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User's Manual for Prediction of Phosphorus Concentration In Nova

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1. 000 RUNOFF ISOLINE 01FA003 WSC STATION NUMBER AND LOCATION Sabie isin Modified from Brimley et al 1985 54 Leer e Manual for Phosphorus Prediction Version 1 0 Appendix IV Literature References for Estimating Export Coefficients Dillon P J and W B Kirchner 1974 The effects of geology and land use on the export of phosphorus from watersheds Water Research 9 135 148 Lowe J S 2001 Revision of the Kings County lake capacity model validation and implications Report prepared for the Municipality of Kings 21p Rast W and G F Lee 1977 Summary analysis of North American U S Portion OECD Eutrophication Project Nutrient loading lake response relationship and trophic status indices Report No EPA 600 3 78 008 Ecological Research Series United States Environmental Protection Agency Corvallis Oregon Reckhow K H M N Beaulac and J T Simpson 1980 Modeling phosphorus loading and lake response under uncertainty A manual and compilation of export coefficients Report No EPA 440 5 80 011 Office of Water Regulations Criteria and Standards Division United States Environmental Protection Agency Washington D C Reckhow K H and S C Chapra 1983 Engineering approaches for lake management Volume I Data analysis and empirical modeling Butterworth Boston Scott R S W C Hart and G Patterson 2000 Phosphorus export from stream catchments in Nova Scotia Internal Report No 93
2. 20 year means from the nearest weather station should be used 7 1 2 3 Annual Unit Lake Evaporation Ev Evaporation from the surface of the lake is required to estimate the lake outflow This parameter is the evaporation rate per square metre per year This information can be also be obtained from the Canadian Climate Normals As is the case for precipitation long term averages should be used 18 Leer Le Manual for Phosphorus Prediction Version 1 0 7 1 2 4 Annual Unit Hydraulic Run Off Ru The average annual unit water run off is the amount of water expressed as m yr this is the same as m m yr that runs off the drainage basin and flows into the lake It represents net run off and is the difference between precipitation and evapotranspiration It should not include groundwater inputs to the lake Ideally this should be estimated from direct measurements made at weirs located at the inputs or outputs of the lake This information however is seldom available and is costly to obtain In most cases it will be necessary to estimate this parameter from other studies An isorunoff map for Nova Scotia is contained in Appendix III and can be used to obtain a rough estimate when more precise data is unavailable 7 1 3 Phosphorus Inputs The most critical data input for the model is the phosphorus loading to the lake This includes both point source loadings such as the effluent of sewage treatment plants and storm
3. PSi Total phosphorus input from Point Source i Nd Number of dwellings in the drainage basin Nu Average number of persons occupying each dwelling Npc Average fraction of the year dwelling are occupied Si Phosphorus load per capita year Rsp Septic system retention coefficient 7 2 2 4 Total Phosphorus Input Jt The Total Phosphorus Input is the sum of all phosphorus inputs to the lake These include upstream phosphorus input atmospheric phosphorus deposition phosphorus surface run off and phosphorus inputs due to development Jt Ji Jd Je Jr where Ji Upstream Phosphorus Input Jd Atmospheric Phosphorus Input Je Surface Run Off Phosphorus Input Jr Development Phosphorus Input 7 2 2 5 Lake Phosphorus Retention Factor Rp The Lake Phosphorus Retention Factor is the fraction of phosphorus entering the lake that is lost by settling to the sediments Rp v v 4qs where v Phosphorus Retention Coefficient qs Areal Hydraulic Load 12 4 for lakes with an oxic hypolimnion and 7 2 for lakes with an anoxic hypolimnion 33 Leer Le Manual for Phosphorus Prediction Version 1 0 7 2 2 6 Lake Phosphorus Retention Ps The amount of phosphorus that is retained in the lake as a result of being lost to the sediments is calculated from the Total Phosphorus Input and the Phosphorus Retention Factor Ps Jtx Rp where Jt Total Phosphorus Input Rp Phosphorus Retention Factor 7 2 2 7 Lake
4. Surface Run Off Phosphorus Input Je gm yr Development Phosphorus Input Jr gm yr Total Phosphorus Input Jt gm yr Lake Phosphorus Retention Factor Rp Lake Phosphorus Retention Ps gm yr Lake Phosphorus Concentration P mg L Total Phosphorus Outflow Jo gm yr Lake Mean Depth Z m Lake Flushing Rate FR times yr Lake Turnover Time TT yr Lake Response Time RT 1 2 yr 7 2 1 Hydrology 7 2 1 1 Total Precipitation Hydraulic Input Ppti The total amount of precipitation input to the lake is calculated as follows Ppti Ao x Pr where Ao Lake Surface Area Pr Annual Unit Precipitation 30 Version 1 0 Leer e Manual for Phosphorus Prediction Version 1 0 7 2 1 2 Total Evaporation Hydraulic Loss Eo The total loss of water due to evaporation from the lake is calculated as follows Eo Ao x Ev where Ao Lake Surface Area Ev Annual Unit Lake Evaporation 7 2 1 3 Total Hydraulic Surface Run Off Ou The total amount of water entering the lake from land run off is calculated as follows Qi Adx Ru where Ad Drainage Basin Area Ru Annual Unit Water Run Off 7 2 1 4 Total Hydraulic Input Qt The Total Hydraulic Input to the lake is calculated as the sum of all water inputs to the lake Qt Ppti QI Qi where Ppti Total Precipitation Input Ql Total Hydraulic Surface Run Off Qi Upstream Hydraulic Input ll 7 2 1 5 Areal Hydraulic Load q The Areal Hydraulic Load to the lake is
5. Percentage Wetland in the Drainage Basin 74 Leer Le Manual for Phosphorus Prediction Version 1 0 VI 2 1 5 Groundwater Inputs The model does not address either the loss of phosphorus to groundwater or the potential for phosphorus input by way of groundwater flows into a lake It is often assumed that groundwater is relatively depleted of phosphorus because of the immobility of phosphorus in soils Although this may be true generally a recent review of phosphorus loss in agricultural drainage Sims et al 1998 indicates that considerable phosphorus can leach into groundwater systems under conditions of deep sandy soils and soils with high phosphorus concentrations resulting from over fertilization or excessive use of organic fertilizers There is also the possibility of groundwater transport to surface run off in agricultural fields that are tile drained This should be considered in model applications where a significant proportion of the lake s drainage basin contains agricultural land use especially if the crops grown receive high levels of fertilization VI 2 2 Lake Morphology Aside from the surface area and indirectly volume of the lake the model does not take into account differences in lake morphology or the position of water inputs to the lake A lake having a complex shoreline with bays and arms may have considerable spatial variation in such things as residence times which in turn could result in considerable variati
6. but it is often accelerated by the activities of humans a process referred to as cultural eutrophication through land use alterations within a lake s drainage basin or by the direct discharge of sewage or other effluents containing nutrients into a lake Although freshwater algae require a number of nutrients in order to grow the two that are most commonly present in limiting amounts are phosphorus and nitrogen Of these phosphorus is the nutrient that most often limits the growth of aquatic plants in freshwater systems and when present in high concentrations is most often responsible for lake eutrophication A general rule of thumb used by limnologists is that phosphorus is considered the limiting nutrient when the ratio of total nitrogen to total phosphorus concentration by weight is greater than about 7 Although there is considerable variation on a global scale the concentration of phosphorus that results in oligotrophic mesotrophic and eutrophic conditions is about lt 10 10 35 and gt 35 ug LU respectively Considerable effort has been devoted to developing quantitative empirical relationships between the concentration of phosphorus in a lake and water quality parameters that provide an indication of the trophic status of a lake The two most commonly used Leer e Manual for Phosphorus Prediction Version 1 0 parameters for this purpose are chlorophyll a concentration an index of the amount of algae contained with
7. mainly hay land 3 2 ha and cottage lots 43 6 ha The area of each was estimated using an image analysis program The following phosphorus export coefficients were estimated from the export coefficients tabulated in Section 7 1 3 3 of the User s Manual e Igneous Forested 0 0069 gm m yr from Scott et al 2000 summary e Managed Forest 0 0625 gm m yr from Maine Department of Environmental Protection 2000 summary e Wetlands 0 0000 gm m yr see discussion in Section 2 1 4 of Supplementary Technical Report e Agriculture mainly hay land 0 0081 gm m yr mean value for grazing pasture from Reckhow et al 1980 in Table 7 4 e Cottage Lots 0 0300 gm m yr from Maine Department of Environmental Protection 2000 summary Donohoe H V and R G Grantham 1989 Geological highway map of Nova Scotia Department of Mines and Energy 4 Finck P W R M Graves F J Bonner and H B Bent 1994 Glacial and till clast geology of Gaspereau Lake Nova Scotia South Mountain Batholith Project Map 94 14 Nova Scotia Department of Natural Resources Cann D B J L MacDougall and J D Hilchey 1965 Soil survey of Kings County Nova Scotia Canadian Department of Agriculture and Nova Scotia Department of Agriculture and Marketing 62 Leer e Manual for Phosphorus Prediction Version 1 0 V 7 Determination of Development Input Development input of phosphorus is determined according to the following
8. or residence Time of a lake is the average amount of time that water remains in the lake It is the reciprocal of the lake s flushing rate and is calculated as follows TT V Qo where V Lake Volume Qo Total Hydraulic Outflow 35 Leer e Manual for Phosphorus Prediction Version 1 0 The longer the residence time the greater the amount of phosphorus that will be subject to sedimentation and lost to the sediments 7 2 3 4 Response Time RT 1 2 The Response Time of a lake is a measure of the time it would take for the lake to respond to a change in its phosphorus loading Response time is a function of the lake s flushing rate and is independent of either the lake s phosphorus load or content Because the rate at which a substance is accumulated or removed from a lake is a logarithmetic function response time is usually expressed as the time it would take to increase or reduce the concentration of a substance by one half and can be estimated by the following equation Dillon and Rigler 1975 RT 1 2 0 69 FR 10 z where FR Flushing Rate of the lake Z Mean Depth of the lake ll II It should be noted that this formulation does not consider the case where a significant portion of the phosphorus within the water column of the lake is a result of internal loading i e the resuspension of phosphorus that has been accumulated within the sediments of the lake 8 Entering Data Entering the data into the
9. uses Pasture log TP export 1 562 0 589 x log Drainage Basin Area Row Crops log TP export 1 880 0 589 x log Drainage Basin Area They suggest these equations be utilized by determining a standardization factor based on drainage basin area Thus if an estimate of the amount of phosphorus exported for a particular land use is to be estimated based on export coefficients obtained from a study carried out in another area the export should be corrected to account for any difference in drainage basin size They provide the following example if the TP export of two row crop catchments 5 and 15 km are to be validly compared the export of the larger basin must be pro rated by a factor of 1 6 72 Leer e Manual for Phosphorus Prediction Version 1 0 the expected TP export from 5 km divided by the expected TP export from 15 km so as to correct for the spatial scale effect observed from this agricultural practice The standardization factor is simply the ratio of the expected TP exports predicted from the above equations for the two catchments VI 2 1 2 Phosphorus Retention in Stream and Rivers The model makes no allowance for the assimilation of phosphorus within upstream rivers or streams entering a lake or for tributaries contained within a lake s drainage basin This is a potentially serious limitation if the model is used to determine the permissible level of development within the watershed of a lak
10. 3 Annual Unit Lake Evaporation os sis esas Ne eeh EE 18 7 1 2 4 Annual Unit Hydraulic Run Off cece cee cece ence eens 19 7 1 3 Phosphorus MOWING ege ER EE deeg 19 7 1 3 1 Upstream Phosphorus Input oo eee cee c cece e eee ee eens 19 7 1 3 2 Annual Unit Atmospheric Deposition 20 7 1 3 3 Annual Unit Phosphorus Export from Land 4 20 7 1 3 4 Development Inputs iacaddianccisiosssasahiaiseiwvarrenverseveanedies 26 7 1 3 5 Point Source EE 27 7 1 3 6 Lake Phosphorus Retention Coefficient eeeeeeee 29 7 2 Model EE 30 iii Leer e Manual for Phosphorus Prediction Version 1 0 E e e E 30 7 2 1 1 Total Precipitation Hydraulic Input 30 7 2 1 2 Total Evaporation Hydraulic Loss 02 0 ceeeeeeeeeeee ee eee ence 31 7 2 1 3 Total Hydraulic Surface Run Off see EENEERR EEN RRE NENNEN 31 7 2 1 4 Total Hydraulic Input gege AER 31 7 2 1 5 Afeal Hydraulic E 31 7 2 1 6 Total Hydraulic Outflow Neuen rege ERAN 32 T22 e cissrr sretni rers Ueaweguveveaniaoronweriexiarsenveneueaerennes 32 7 2 2 1 Atmospheric Phosphorus Input 32 7 2 2 2 Total Surface Run Off Phosphorus Input 32 7 2 2 3 Development Phosphorus Input 33 7 2 2 4 Total Phosphorus Input 33 7 2 2 5 Lake Phosphorus Retention Factor cceeeeeeeeeeeeeeees 33 7 2 2 6 Lake Phosphorus Retention sde egdr ceded eureuciss Clow iacers 34 7 2 2 7 Lake Phosphorus Concentration cccceee eee eee seen es
11. Category 6 P Export Coefficient E6 0 0000 gmPm yr Difference 21 9 Land Use Category 7 P Export Coefficient E7 0 0000 gm Pm yr Land Use Category 8 P Export Coefficient E8 0 0000 gm Pm yr Land Use Category 9 P Export Coefficient EQ 0 0000 gm P m yr Land Use Category 10 P Export Coefficient E10 0 0000 gm P m yr Number of Dwellings Nd 110 Average number of Persons per Dwelling Nu 2 73 Average Fraction of Yr Dwellings Occupied Npc 0 22 De This includes only the input from septic systems It could also and probably should include the increase in run off of phosphorus from dwelling lots above that which would occur if the lots were left as forest land 64 Leer e Manual for Phosphorus Prediction Version 1 0 Phosphorus Load per Capita per Year Si 800 gm P cap yr Septic System Retention Coefficient Sr 0 5 n a Point Source Input 1 PS1 0 gm vr Point Source Input 2 PS2 0 gm vr Point Source Input 3 PS3 0 gm vr Point Source Input 4 PS4 0 gm vr Point Source Input 5 PSs 0 gm yr Phosphorus Retention Coefficient v 7 2 n a Model Outputs Total Precipitation Hydraulic Input Ppti 1750991 m yr Total Evaporation Hydraulic Loss Eo 260478 m yr Total Hydraulic Surface Run Off O 5982400 m vr Total Hydraulic Input Qt 773391 m yr Areal Hydraulic Load qs 5 16 m yr Total Hydraulic Outflow Qo 7472913 m yr Upstream P Input Jd 0 gm vr Total Atmospheric P Input Jd 28942
12. Category 8 P Export Coefficient E8 gm P mur Land Use Category 9 P Export Coefficient E9 gm P m yr Land Use Category 10 P Export Coefficient E10 om Pm yr Number of Dwellings Nd Average Number of Persons per Dwelling Nu Average Fraction of Year Dwellings Occupied Npc yr Phosphorus Load per Capita per Year Si gm capita yr Septic System Retention Coefficient Rsp n a Point Source Input 1 PS1 gm yr Point Source Input 2 PS2 gm yr Point Source Input 3 PS3 gm yr Point Source Input 4 PS4 gm yr Point Source Input 5 PS5 gm yr Lake Phosphorus Retention Coefficient v n a Model Outputs Total Precipitation Hydraulic Input Ppti m yr Total Evaporation Hydraulic Loss Eo m yr Total Hydraulic Surface Run Off Ql m yr Total Hydraulic Input Qt m yr 51 User s Manual for Phosphorus Prediction Version 1 0 Areal Hydraulic Input qs m yr Total Hydraulic Outflow Qo m yr Total Atmospheric P Input Jd gm vr Total Surface Run Off P Input Je gm vr Total Development P Input Jr gm vr Total P Input Jt gm vr Lake P Retention Factor Rp S Lake P Retention Ps gm vr Predicted Lake P Concentration P mg L Lake P Outflow Jo gm yr Lake Mean Depth Zz m Lake Flushing Rate FR times vr Lake Turnover Time TT Lake Response Time RT 1 2 52 Leer e Manual for Phosphorus Prediction Version 1 0 Appendix II Data Sources Lake Morphology Information Officer Nova Scotia
13. D A Hammer ed Constructed wetlands for wastewater treatment Municipal industrial and agricultural Lewis Publishing Hutchinson N J 2002 Limnology plumbing and planning Evaluation of nutrient based limits to shoreline development in Precambrian Shield watersheds p 647 680 Jn R L France ed Handbook of water sensitive planning and design Lewis Publishing 80 Leer e Manual for Phosphorus Prediction Version 1 0 Jackson T A and R E Hecky 1980 Depression of primary productivity by humic matter in lake and reservoir waters of the boreal forest zone Can J Fish Aquat Sci 37 2300 2317 Jorgenson 1995 State of the art of ecological modeling in limnology Ecol Mod 78 101 115 Kennedy R H 1998 Basinwide considerations for water quality management Importance of phosphorus retention by reservoirs Water Quality Technical Note MS 03 United States Army Corps of Engineers Vicksberg MS Kerekes J 1981 Atlantic Region p 1 13 Jn Janus L L and R A Vollenweider eds Summary Report of the OECD Cooperative Programme on Eutrophication Canadian Contribution Scientific Series No 131 National Water Research Institute Inland Water Directorate Canadian Centre for Inland Waters Burlington Ontario Knight R L T W McKim and H R Kohl 1987 Performance of a natural wetland treatment system for wastewater management J Wat Poll Control Fed 59 8 746 754 Lee G F R A Jones and W Ras
14. Excel spreadsheets is quite straight forward for most of the input parameters The only potential difficulty that may be encountered is in the case where more than one upstream input enters the lake In this instance it will be necessary to develop a customized formula for the Excel cells to sum all of the upstream water and phosphorus inputs It is also important to zero out any inputs listed on the spreadsheet that may not be applicable for the lake being modeled 36 Leer Le Manual for Phosphorus Prediction Version 1 0 9 Model Validation Validation of the model is necessary before it can be used with confidence for prediction and as a basis for making policy decisions Model validation simply involves comparing the model s prediction with data collected in the field As a general rule the model can be considered valid if the model prediction and field measurements of phosphorus concentration do not differ by more than about 20 a value that is considered to reflect the confidence limits of most field and laboratory measurements It is important to realize that the model is likely to have been constructed using parameter estimates that are averages of many years and that the validation data should also be representative of an average year Mean annual lake phosphorus concentrations can vary considerably from year to year and it is necessary to collect the validation data over a number of years to determine a reasonable average Althoug
15. Land Use Category 4 P Export Coefficient E4 0 0081 om Pm ur Measured P mg L 0 0105 Land Use Category 5 P Export Coefficient ER 0 0300 gm P m yr Predicted P mg L 0 0084 Land Use Category 6 P Export Coefficient E6 0 0300 gmPm yr Difference 20 0 Land Use Category 7 P Export Coefficient E7 0 0000 gm Pm yr Land Use Category 8 P Export Coefficient E8 0 0000 gmPm yr Land Use Category 9 P Export Coefficient E9 0 0000 gmPm yr Land Use Category 10 P Export Coefficient E10 0 0000 gmPm yr Number of Dwellings Nd 110 Average number of Persons per Dwelling Nu 2 73 n a Average Fraction of Yr Dwellings Occupied Npc 0 22 yr Phosphorus Load per Capita per Year Si 800 gm P cap yr Septic System Retention Coefficient Rsp P Input from camp PS1 gm yr P input from public beach PS2 gm yr Point Source Input 3 PS3 0 gm yr Point Source Input 4 PS4 0 gm yr Point Source Input 5 PS5 0 gm yr Phosphorus Retention Coefficient v 7 2 n a Model Outputs Total Precipitation Hydraulic Input Ppti 1750991 m yr Total Evaporation Hydraulic Loss Eo 260478 m vr Total Hydraulic Surface Run Off QI 5982400 m yr Total Hydraulic Input Qt 7733391 m vr Areal Hydraulic Load qs 5 16 m yr Total Hydraulic Outflow Qo 7472913 m vr Total Atmospheric P Input Jd 28942 gm yr Total Surface Run Off P Input Je 91369 gm yr Total Development P Input Jr 29026 gm yr Total P Input Jt 149337 gm yr Lake P Retention Factor Rp 0 58 n a Lake Phosphorus Retenti
16. Phosphorus Concentration P The Lake Phosphorus Concentration is calculated as the Total Phosphorus Input minus the amount lost to sedimentation divided by the Total Hydraulic Outflow P Jt Ps Qo where Jt Total Phosphorus Input Ps Phosphorus Retention Qo Total Hydraulic Outflow II 7 2 2 8 Lake Phosphorus Outflow Jo The amount of phosphorus that flows out of the lake is the difference between the total phosphorus input and the amount of phosphorus retained by the lake as a result of settling to the sediments Jo Jt Ps where Jt Total Phosphorus Input Ps Lake Phosphorus Retention 34 Leer e Manual for Phosphorus Prediction Version 1 0 7 2 3 Lake Characterization Parameters The following parameters essentially characterize the lake s hydraulic characteristics and can be important in determining the choice of formulations to use for calculation of phosphorus retention They all require that the volume of the lake be known 7 2 3 1 Mean Depth z The Mean Depth of the lake is calculated as the ratio of the surface area and volume of the lake z Ao V_ where Ao Lake Surface Area V Lake Volume 7 2 3 2 Flushing Rate FR The Flushing Rate is the number of times a volume of water equal to the volume of the lake flows through the lake per year It is calculated as FR Qo V where Qo Total Hydraulic Outflow V Lake Volume 7 2 3 3 Turnover Time TT The Turnover
17. TEMPERATURE C 0 10 20 30 EPILIMNION HYPOLIMNION Figure 2 1 Cross section through a stratified lake showing the three water layers and a temperature depth profile Lake stratification typically begins during spring when daylength increases and the lake begins to warm It ends in the fall when daylength begins to decrease and the surface water cools causing it to sink to the bottom of the lake At this time the lake undergoes the fall overturn and the bottom waters rise to the surface having been displaced by the sinking surface waters This process results in bottom waters becoming re oxygenated in those instances when the lake has experienced a decrease in oxygen during the period of summer stratification Temperate zone lakes may also undergo stratification during winter if covered by ice and this may also result in depletion of oxygen in the bottom waters Figure 2 2 illustrates the seasonal variation in thermal structure of a lake that undergoes stratification One of the most significant consequences of stratification is that it limits the degree to which oxygen is mixed from the surface of the lake to the hypolimnion As a result if the lake has a high level of algal production the dead organic matter that eventually results settles to the Leer Le Manual for Phosphorus Prediction Version 1 0 bottom of the lake where it is metabolized by organisms that consume whatever oxygen was present when the lake first strati
18. analysis of field samples will be done at an accredited laboratory having the capability of processing samples for water quality and especially for carrying out total phosphorus analyses at a detection limit of 0 001 mg L 10 Model Re evaluation If the model does not predict well when compared to the validation data it must be re evaluated Re evaluation involves assessing each input parameter in terms of its accuracy It may also require that the processes incorporated into the model be re evaluated For example if the lake is stratified it may be necessary to alter the way in which sedimentation rate is modeled 11 Sensitivity Analysis Carrying out a sensitivity analysis can be quite insightful in terms of understanding which factors exert the most influence in determining the level of phosphorus predicted by the model It is also useful in determining where the greatest effort should be placed in refining the model if it does not meet the validation criteria As an example a sensitivity analysis of the Gaspereau River watershed model indicated that the prediction of phosphorus concentration was most sensitive to the phosphorus land run off coefficients and the lake phosphorus retention coefficient The general procedure for carrying out a sensitivity analysis is to alter the value of each model input parameter by a constant percentage while holding all other parameters 38 Leer e Manual for Phosphorus Prediction Version
19. equation Pd amp PSi Nd x Nu x Npe x Si x 1 Rsp where PSi Total phosphorus input from Point Source i Nd Number of dwellings in the drainage basin Nu Average number of persons occupying each dwelling Npc Average fraction of the year dwelling are occupied Si Phosphorus load per capita year Rsp Septic system retention coefficient Development on Lake George is due to residential use most of which is summer cottages The number of cottages and permanent residences located within 300 metres of the shoreline of the lake was determined from statistics compiled by the Municipality of Kings County Information on the frequency of occupancy and number of persons using each residence was obtained through a mail out survey The number of dwellings Nd was determined to be 110 Of these 104 are seasonal and 6 are permanent Results of the survey indicated that the average number of persons occupying each dwelling was 2 73 for the seasonal dwellings and 3 20 for the permanent dwellings The average fraction of the year each dwelling was occupied was 0 19 for the seasonal dwellings and 0 82 for the permanent dwellings Based on this information the average number of occupants Nu and the average fraction of the year occupied for seasonal and permanent dwellings Npe combined were calculated to be 2 73 and 0 22 The phosphorus load per capita Si was considered to be 800 gm P yr and the septic system retention coefficien
20. eutrophication in the Maritime Provinces Wat Poll Cont September 99 100 Waller D H and W C Hart 1986 Solids nutrients and chlorides in urban run off p 59 85 In H C Torno J Marsalek and M Desbordes eds Urban run off pollution Springer Verlag Berlin Wetzel R G 1983 Limnology 2 ed Saunders Wetzel R G and G E Likens 1991 Limnological analyses 277 ed Springer Verlag New York 46 Leer e Manual for Phosphorus Prediction Version 1 0 14 Glossary Algae A general term applied to aquatic photosynthetic organisms Anaerobic life without oxygen Anoxic having no oxygen Catchment Area See watershed Chlorophyll a The major photosynthetic pigment present in algae and other plants Measurement of its concentration in a water body is used as an indication of algal biomass Drainage Basin The land area from which water runs off to drain into a stream river lake or estuary Epilimnion The upper warmer surface layer of a stratified lake Export coefficient A measure of the amount of a substance exported from a system f ys 1 usually expressed as mass area time Export Coefficient Model A model for calculating nutrient loads to an aquatic ecosystem based on knowledge of land use and other drainage basin characteristics Eutrophic A measure ofa lake s trophic status Literally means well nourished and applied to aquatic ecosystems exhibiting a high level
21. lake phosphorus concentration The spatial extent of the watershed required for the model depends on the relationship of the lake being modeled to other lakes Ifthe lake is a headwater lake then only its watershed needs to be included in the model If however the lake receives inputs from lakes located upstream the watersheds of those lakes will also have to be included in the model Leer Le Manual for Phosphorus Prediction Version 1 0 The mathematical formulation of the model is best described as a black box mass balance steady state model The term black box implies that the model does not attempt to include any of the processes involved in determining the amount of phosphorus entering the lake nor any of the biological or chemical processes that phosphorus goes through once it enters the lake The term mass balance indicates that the model is essentially a budget of the amount of phosphorus entering and leaving the lake and the term steady state means that on an annual time scale the amount of phosphorus entering the lake is equal to the sum of that which sediments to the bottom and that which leaves the lake via its outflow The model is essentially an accounting system that sums the hydraulic inputs phosphorus inputs and amount of phosphorus lost to the sediments to estimate the phosphorus concentration of the lake Figure 3 2 illustrates this further Atmospheric Phosphorus Precipitation Evaporation Deposition Lake P
22. of productivity see Table 1 Flushing Rate The number of times a volume of water equal to the volume of the lake flows out of the lake Itis calculated as the ratio of the volume of water leaving the lake to the volume of the lake usually on an annual basis 47 Leer e Manual for Phosphorus Prediction Version 1 0 Hypolimnion The lower colder water later of a stratified lake Hypoxia having low generally lt 2 3 mg L dissolved oxygen Internal Nutrient Loading The release of nutrients from sediments into the water column Mesotrophic A measure of a lake s trophic status Literally means moderately nourished and applied to lakes exhibiting a moderate level of productivity see Table 1 Metalimnion The middle layer of a stratified lake containing an area of rapid temperature change the thermocline Non point Pollution Source A nutrient or other pollutant source that originates from a diffuse area of the watershed as opposed to a clearly identified single source Oligotrophic A measure of a lake s trophic status Literally means poorly nourished and applied to lakes exhibiting a low level of productivity see Table 1 Oxic having oxygen Point Source Pollutant A pollutant that originates from a single easily identified location such as a sewage treatment plant Residence Time See Turnover Time Response Time The time it would take for the lake to respond to a cha
23. of the model it was discovered that Lake George has a summer camp located on its north shore The camp accommodates 34 persons per day for a period of 14 days which is equivalent to 476 user days per year or 1 30 capita per year Assuming a septic input of 800 gm P per capita per year and a septic retention coefficient of 0 5 this would result in an input of 520 gm P per year The area of land used for the camp should also be considered and it was assumed that it occupied an area of five ha and had a phosphorus export coefficient of 0 0300 gm m yr equal to that of the cottage lots Further re evaluation indicated that Lake George also contains a public beach Data on the per capita use of the public beach is not available but if it is conservatively assumed that phosphorus inputs from this source are equal to about four times that of the summer camp this addition results in a difference of 20 0 which is on the borderline of the of the 20 guideline Other factors that could also be re evaluated include inputs from roadways along the lake s shoreline and the assumption that there is no phosphorus export from the wetland present in the drainage basin The validated model is illustrated below the input values that were changed or added in the re evaluation process are in bold print Lake George Validated Model Input Parameters Symbol Budgets Morphology Drainage Basin Area Excl of Lake Area Ad Hydr
24. the amount of water entering the lake relative to the surface area of the lake It is calculated as the ratio of the total annual water input minas evaporation and the lake surface area qs Qt Eo Ao where 31 Leer e Manual for Phosphorus Prediction Version 1 0 Qt Total Hydraulic Input Eo Evaporation Hydraulic Loss Ao Lake Surface Area ll 7 2 1 6 Total Hydraulic Outflow Qo The Total Annual Hydraulic Outflow is calculated as the Total Hydraulic Input minus Evaporation for the lake surface Qo Qt Eo where Qt Total Hydraulic Input Eo Evaporation Loss 7 2 2 Phosphorus 7 2 2 1 Atmospheric Phosphorus Input Jd The Atmospheric Phosphorus Input is calculated as the product of the Annual Unit Atmospheric Deposition and the Lake Surface Area Jd Dx Ao where D Annual Unit Atmospheric Deposition Ao Lake Surface Area 7 2 2 2 Total Surface Run Off Phosphorus Input Je The Total Surface Run Off Phosphorus Input is the sum of all the phosphorus export from each land use class Je Adi x Ei where Adi Area of land use i Ei Annual unit phosphorous export from land use i 32 Leer Le Manual for Phosphorus Prediction Version 1 0 7 2 2 3 Development Phosphorus Input Jr The Development Phosphorus Input is the sum of phosphorus inputs from all point sources and dwellings within the lake s drainage basin Jr amp PSi Nd x Nu x Npe x Si x 1 Rsp where
25. the model and observing the resulting changes They also provide an important means of evaluating how well we understand a system by comparing model predictions to what occurs in nature If the model replicates what occurs in nature we can have some confidence in believing that it contains all the important elements that control a particular process If however the model behaves differently from what we observe in nature this is an indication that the model lacks important qualitative elements or is not correct in its quantitative formulations If the model does appear to work well in terms of its predictive ability we then have a tool that we can use to make management decisions The phosphorus run off coefficient modeling approach is one of the simplest approaches available to evaluate potential changes in phosphorus concentration resulting from changes in land use activities This simplification has both its advantages and disadvantages Its main advantage is that it is relatively easy to apply does not require a great deal of costly field work for estimation of parameters and most importantly it provides for a relatively standardized procedure for making the best guess when a 70 Leer e Manual for Phosphorus Prediction Version 1 0 decision has to made based on the potential impact of a particular development scenario being proposed for a watershed Because the model is simple its main disadvantage is that it has a number
26. 1 0 constant and then determining the percent change in the model s predictions A factor of ten percent is typically used and because there is some non linearity in the model it is always a good idea to both increase and decrease the input In some cases such as inputs related to precipitation it may be instructive to alter the input parameter by a factor that corresponds to how much the parameter is known to vary on an annual basis 12 Acknowledgements Funding to develop this User s Manual was provided by the Nova Scotia Department of Environment and Labour the Nova Scotia Department of Natural Resources the Nova Scotia Department of Transportation and Public Works and Environment Canada The manual was developed under the direction of the following members of the Nova Scotia Water Quality Objectives and Model Development Steering Committee Darrell Taylor Environmental Analyst Committee Chair Nova Scotia Department of Environment and Labour Andrew Bagnall Supervisor of Extension Services Nova Scotia Department of Agriculture and Fisheries Anthony Blouin Manager Environmental Policy Environmental Management Services Halifax Regional Municipality David Briggins Manager Water and Wastewater Branch Nova Scotia Department of Environment and Labour Graham Fisher Watershed Planner Nova Scotia Department of Environment and Labour John Gibb Regional Hydrogeologist Integration and Interpretation Section Environment C
27. 3 DalTech Dalhousie University Halifax Nova Scotia 102 p Uttomark P D J D Chapin and K M Green 1974 Estimating nutrient loading of lakes from non point sources Report No 660 13 74 020 Ecological Research Series United States Environmental Protection Agency Corvallis Oregon 55 Leer e Manual for Phosphorus Prediction Version 1 0 Appendix V Example of Model Application This appendix contains an example of the application of the model to Lake George a headwater lake located in the Gaspereau River watershed in Kings County Nova Scotia Development of each model input is explained according to the order in which they are presented in the manual and listed in the Excel worksheet 56 Leer e Manual for Phosphorus Prediction Version 1 0 V 1 Determination of Drainage Basin Area The area of the drainage basin is determined by outlining the drainage basin on a topographic map Figure V 1 and determining its area using planimetry the actual size of the map used for this was at a scale of 1 5 000 The drainage basin surface area was determined to be 747 8 ha PT ea LN y Lake George f J Drainage Basin 200 D 200 400 Meters ELE Figure V 1 Map of Lake George showing its drainage basin 57 Leer e Manual for Phosphorus Prediction Version 1 0 V 2 Determination of the Area of Each Land Use Category The area of each land use is determined by subdividing the drainage basin into land use categories Fo
28. 34 7 2 2 8 Lake Phosphorus Outflow Ave cudevssarsvenesedauwesnavetuasnedsis 34 7 2 3 Lake Characterization Parameters eene genge geed eeegA EA 35 Tid ie Mean Depth dreet eh Eeer 35 Fo Flushing Rate AE 35 dot en erte geb EE 35 7 2 3 4 Response EE 36 Sy Entering Data eege 36 9 Model Werer Let genee 37 9 1 Protocol for Collection of Validation Data 37 Et Bee 38 11 Sensitivity Analysis wc ssacesesoedsoanecandneessnenednsurenonnetacandssancbivawecars 38 12 Acknowledgements enden deeg de E E ANENE EE EREE e eg 39 E EE 41 l4 Glossary EE 47 15 APPEndICES euer 50 Appendix I Sample Excel Worksheet 00 0 cece cece ec eceneea eens 51 iv Leer Le Manual for Phosphorus Prediction Version 1 0 Appendix II Data Sources sicissepssncncessiawe EE ENEE 53 Appendix III Isorunoff Map for Estimating Surface Run Off 54 Appendix IV Literature References for Estimating Export Coefficients 55 Appendix V Example of Model Application cceeeee eee ee ees 56 V 1 Determination of Drainage Basin Area cecee cence ees 57 V 2 Determination of the Area of Each Land Use Category 58 V 3 Determination of Hydrological Inputs Outputs 59 NA Determination of Lake Surface Area and Volume 60 V 5 Estimate of Atmospheric Phosphorus Deposition Coefficient 62 No Estimates of Phosphorus Land Use Run Off Coefficients Gi V 7 Determination of Devel
29. 6 Non row Crops 0 0010 0 0290 0 0076 0 0108 Grazing Pasture Land 0 0014 0 0490 0 0081 0 0150 Run off coefficients for land uses other than those listed above will have to be estimated from literature containing coefficients measured in other regions of North America See Appendix IV for literature references of compiled export coefficients It should be noted that the utmost care should used in deciding if an estimate is really applicable to the situation that exists in the watershed being modeled Export coefficients are among the most sensitive parameters determining the level of phosphorous concentration predicted by the model 25 Leer e Manual for Phosphorus Prediction Version 1 0 Urban Run Off Urban areas typically have a high run off of phosphorus Sources include run off from pavement roads parking lots and driveways and lawns and leaf fall Reckhow et al 1980 list a wide variety of export coefficients for urban areas ranging from 0 0019 to 0 0623 gm m vr The lowest values were for areas of low density housing and the highest for high density housing areas Waller and Hart 1986 estimated surface run off from urban areas in Ontario to be about 0 11 emm yr They also presented the following estimates for impervious urban areas in Halifax Residential Vegetation Low Traffic 0 186 gm m yr Commercial No Vegetation High Traffic 0 202 gm m yr Commercial Vegetation Moderately High
30. 8 Sedimentary Medium Fine 89 4 3 4 0 0213 Sedimentary Fine Coarse 98 1 0 1 0 0191 Sedimentary Medium Fine 74 4 0 22 0 0311 Sedimentary Medium Fine 72 8 0 20 0 0321 Igneous Fine Coarse 69 6 2 23 0 0624 Some phosphorus export coefficient estimates are also available for Maine which has similar climate geological and soil characteristics to Nova Scotia The following export 24 Leer e Manual for Phosphorus Prediction Version 1 0 coefficients were established by the Maine Department of Environmental Protection 2000 based on an extensive survey of values reported in the literature e Managed Forests ca 15 clearcut 10 selective cut 0 050 0 075 gm m yr e Unmanaged Forest 0 0035 0 0050 gm m yr e Agriculture Rotation Crops 0 150 0 350 gm m yr e Agriculture Using Soil Conservation Practices 0 010 0 030 gm m yr e Residential Lots 0 025 0 035 gm m yr e Logging Roads 0 35 gm m yr e Public Highways 0 35 gm m yr e Camp Private Roads 0 35 gm m yr Reckhow et al 1980 carried out and an extensive literature survey of export coefficients and compiled the summary listed in Table 7 4 Table 7 4 Summary of land use phosphorus export coefficients gm m yr compiled by Reckhow et al 1980 Land Use Range Median Mean Forest 0 0019 0 0083 0 0021 0 0024 Row Crops 0 0026 0 1860 0 0224 0 044
31. 9 A note on error analysis for a phosphorus retention model Water Resour Res 15 1643 1646 Reckhow K H M W Beaulac and J T Simpson 1980 Modeling phosphorus loading and lake response under uncertainty A manual and compilation of export coefficients U S Environmental Protection Agency EPA 440 5 80 011 Sas H 1989 Lake restoration by reduction of nutrient loading Expectations experiences and extrapolations Academia Verl St Augustin Scott R S W C Hart and G Patterson 2000 Phosphorus export from stream catchments in Nova Scotia Internal Report No 93 3 DalTech Dalhousie University Halifax Nova Scotia 102 p 44 Leer e Manual for Phosphorus Prediction Version 1 0 Scott R S J Lowe and S Mandaville 2003 Selection of phosphorus loading model for Nova Scotia Phase I Report prepared for the Nova Scotia Department of Environment and Labour 74 p Soil and Water Conservation Society of Metro Halifax 1992 Theoretical phosphorus loading in 27 Halifax County lakes Soil and Water Conservation Society of Metro Halifax Dartmouth Nova Scotia Soil and Water Conservation Society of Metro Halifax 1993 Theoretical phosphorus loading to 25 Halifax County lakes Phase B2 limnology project September 1993 Soil and Water Conservation Society of Metro Halifax Dartmouth Nova Scotia Thirumurthi R D and W C Hart 1985 Chemistry of bulk deposition in Halifax and its effects on Chain and Chocolate la
32. Department of Agriculture and Fisheries P O Box 700 Pictou N S BOK HO Tel 902 485 5056 http www gov ns ca nsaf sportfishing lakesurvey Drainage Basin Topographic Maps Nova Scotia Geomatics Centre Service Nova Scotia and Municipal Relations 160 Willow Street 5151 Terminal Road Amherst N S P O Box 2205 B4H 3W5 Halifax N S Tel 902 667 721 B3J 3C4 Fax 902 667 6299 Tel 902 424 2735 http www gov ns ca snsmr land Fax 902 424 5747 email lic_hfx gov ns ca Climate Meteorology Environment Canada Canadian Climate Normals http www climate weatheroffice ec gc ca climate_normals index_e html Geology Nova Scotia Department of Natural Resources Mineral Resources Branch 1701 Hollis Street Founders Square 3rd Floor Halifax N S B3J 3M8 Tel 902 424 2035 Fax 902 424 7735 http www gov ns ca natr meb pubs pubshome htm Soil Characteristics Nova Scotia Department of Agriculture and Marketing Soils Survey Reports Agriculture and Agri Food Canada 1999 Canadian Soil Information Systems National Soil Database http sis agr gc ca cansis Land Use and Population Statistics Local Municipal Planning Offices 53 Leer e Manual for Phosphorus Prediction Version 1 0 Appendix III Isorunoff Map for Estimating Surface Run Off HYDROLOGIC NETWORK REVIEW NOVA SCOTIA A_JOINT FEDERAL PROVINCIAL PROJECT ISOGRAM OF MEAN ANNUAL RUNOFF INSET t50 IN MILLIMETRES FOR PERIOD 1969 1983 LEGEND
33. Excl of Lake Area Ad Hydraulic Budget m Area Land Use Category 1 Total Area Land Use Category 2 Upstream Inflow Area Land Use Category 3 Area Land Use Category 4 Precipitation Surface Run Off Area Land Use Category 5 Evaporation Area Land Use Category 6 Total Outflow Area Land Use Category 7 Area Land Use Category 8 Area Land Use Category 9 Phosphorus Budge Area Land Use Category 10 Lake Surface Area Upstream Inflow Lake Volume Atmosphere Hydrology Inputs Surface Run Off Upstream Hydraulic Inputs Qi Development Annual Unit Precipitation Pr Sedimentation Annual Unit Lake Evaporation Annual Unit Hydraulic Run Off Ev m yr Phosphorus Inpu Upstream P Input gm P yr Total Outflow Model Validation Predicted P mg m Annual Unit Atmospheric Phosphorus Deposition gm P m yr Measured P mg m Land Use Category 1 P Export Coefficient gm P m yr Difference Land Use Category 2 P Export Coefficient Land Use Category 3 P Export Coefficient Land Use Category 4 P Export Coefficient Land Use Category 5 P Export Coefficient gm P m yr gm P m yr gm P m yr gm P m yr Land Use Category 6 P Export Coefficient E6 gm P m yr Land Use Category 7 P Export Coefficient E7 gm P m yr Land Use
34. Traffic 0 398 gm m yr Institutional No Vegetation Low Traffic 0 042 gm m yr 7 1 3 4 Development Inputs Nd Nu Npc Si Rsp Development input is the amount of phosphorus supplied to the lake from the human population present in the watershed It is based on a determination of the number of capita years in the watershed the amount of phosphorus produced per capita and the proportion of the phosphorus produced that enters the lake It also includes point source inputs of phosphorus Although some of this information may be available from local planning offices it will most likely have to be gathered from surveys The information required to estimate the number of capita years is as follows e Nd the number of dwelling units within 300 m of the shoreline of the lake and any tributaries that enter into the lake e Nu the average number of people occupying the dwellings e Npc the average fraction of the year each dwelling is occupied 26 Leer e Manual for Phosphorus Prediction Version 1 0 The amount of phosphorus produced per capita Si depends on the nature of the activities of the population residing in the watershed and whether the residences are simple recreational cottages or full time residences Factors such as the use of fertilizer for gardening and lawn maintenance use of phosphate based detergents and prevalence of garbage grinders are some of the factors that should be considered Estimates of the amount of phos
35. User s Manual for Prediction of Phosphorus Concentration In Nova Scotia Lakes A Tool for Decision Making Version 1 0 Prepared For The Nova Scotia Water Quality Objectives and Model Development Steering Committee Nova Scotia Department of Environment and Labour By M Brylinsky Acadia Centre for Estuarine Research Acadia University Wolfville Nova Scotia B4P 2R6 January 2004 gt 4 NOVA SCOTIA ACADIA Ka Ld CENTRE FOR ESTUARINE RESEARCH Environment and Labour Leer e Manual for Phosphorus Prediction Version 1 0 SUMMARY Increasing demands on our freshwater resources to provide clean water for industrial domestic agricultural and recreational purposes together with increasing development of watersheds has raised concerns about the kind and amount of development that can be tolerated in watersheds containing these resources Of major concern are watershed activities that result in increased inputs of phosphorus to lakes the nutrient most important in controlling lake productivity and when present in high concentrations the major cause of lake eutrophication As a result considerable effort has been extended by various agencies to develop methods that can be used to determine the extent to which a watershed can be altered before the aquatic ecosystems it contains begin to exhibit impaired water quality This manual documents a simple modeling procedure that has been widely used to predict the amount of phosphoru
36. ailable In this case the phosphorus may become resuspended into the water column where it is available for uptake by plants This chemical transformation of insoluble phosphorus to a soluble form under anoxic conditions is one of the reasons why a lake that has accumulated phosphorus in its sediments over a long period of time and that has an anoxic hypolimnion may take considerable time often on the order of decades to respond to a reduction in phosphorus loading AIPO Streams R vm tem INPUTS FePO gt Erosion Aerial Deposition gt 90 Ge pe P Loading MgPO 10 PO 90 PP lt 10 Bacterioplankton Particulate P n organic detritus 90 Phytoplankton Zooplankton Organic Sediments Sediment e g Ca PO Fe PO Figure 2 3 The cycle of phosphorus in a lake percentages represent the relative amounts of phosphorus typically found in each form within the water column of a lake Modified from Horne and Goldman 1994 Plants can only assimilate phosphorous in the dissolved inorganic form This form is referred to as orthophosphate and because of the rapidity with which plants take it up it is usually present in very low amounts Orthophosphate that has been taken up by plants Leer e Manual for Phosphorus Prediction Version 1 0 becomes incorporated into the food web as living particulate phosphorus This pool of phosphorus is much larger than that present as orthophosphate As organisms die an
37. ake and the way in which lake stratification and the mixing processes occurring within the water column of a lake influence this cycle It is also important to know something of the relationship between light availability and lake stratification in terms of how this also influences lake productivity The discussion below provides a general description of these factors 2 1 Lake Stratification Lake stratification refers to the condition in which the water column of a lake becomes separated into layers of different densities as a result of differences in temperature In temperate climates this stratification is typically most strongly developed during the late summer and consists of three water layers Figure 2 1 The upper surface portion of the water column the epilimnion is the warmest layer and the lower bottom layer the hypolimnion is the coldest Between the two is the metalimnion a layer of water in which a strong temperature gradient called the thermocline exists In Nova Scotia the depth of the thermocline during the summer is generally about six metres unless the lake is colored in which case the thermocline forms at about three Leer e Manual for Phosphorus Prediction Version 1 0 metres Aside from color the strength and depth of the thermocline as well as the temperature difference between the epilimnion and hypolimnion depends on a number of factors of which exposure to winds is one of the most important
38. al Protection Agency Washington D C EPA 822B00 001 Wagner R A T S Tisdale and J Zhang 1996 A framework for phosphorus transport modeling in the Lake Okeechobee watershed Wat Res Bull 31 1 57 73 Welch E B and G D Cooke 1995 Internal phosphorus loading in shallow lakes importance and control Lake and Reserv Manage 11 3 273 281 82
39. anada Robert Gordon Associate Professor Resource Stewardship Department of Agriculture Engineering Nova Scotia Agricultural College William Hart Director Centre for Water Resources Studies Dalhousie University 39 Leer e Manual for Phosphorus Prediction Version 1 0 Joseph Kerekes Scientist Emeritus Conservation and Protection Branch Environment Canada Scott Lister Watershed Planner Nova Scotia Department of Environment and Labour Jonathan Lowe Fisheries Representative Nova Scotia Department of Agriculture and Fisheries Michael MacIntyre Senior Planner Community Planning Department Municipality of Kings County John MacMillan Fisheries Biologist Recreational Fisheries Nova Scotia Department of Agriculture and Fisheries Alan McNeill Aquaculture Coordinator Nova Scotia Department of Agriculture and Fisheries Vincent Mercier Environmental Indicator and Reporting Specialist Environment Canada Randy Milton Manager Wildlife Resources Nova Scotia Department of Natural Resources Jordan Mooers Hydrogeologist Nova Scotia Department of Transportation and Public Works Richard Scott Senior Research Associate Centre for Water Resources Studies Dalhousie University Wesley White Biologist retired Science Branch Department of Fisheries and Oceans David Wigmore Senior Manager Nova Scotia Department of Environment and Labour Special thanks are due Michael MacIntyre and David Poole of the Kings County Planning Office wh
40. aulic Budget m Area Land Use Category 1 Forest Area Land Use Category 2 Clear Cut Ad1 Total Upstream Inflow 0 Precipitation 1750991 Area Land Use Category 3 Wetland Area Land Use Category 4 Hay Land Area Land Use Category 5 Cottage Lots Land Run Off 5982400 Evaporation 260478 Area Land Use Category 6 Campground Ad6 ha Total Outflow 7472913 96 63 Area Land Use Category 7 Ad7 0 0 ha Total Check 100 00 Area Land Use Category 8 Ad8 0 0 ha Area Land Use Category 9 Ad9 0 0 ha A Area Land Use Category 10 Ad10 0 0 ha E Lake Surface Area Ao 144 7 ha Total Lake Volume V 6 72 10 m Upstream Inflow 0 0 Hydrology Atmosphere 28942 19 38 Upstream Hydraulic Inputs Qi 0 m vr Surface Run Off 91369 61 18 Annual Unit Precipitation Pu 1 21 myr Development 29026 19 44 Annual Unit Lake Evaporation Eu 0 18 m vr Sedimentation 86615 58 00 Annual Unit Hydraulic Run Off Ru 0 80 m vr Total Outflow 62722 42 00 Phosphorus Inputs Total Check 100 00 Upstream P Input Ju 0 gm P yr Annual Unit Atmospheric P Deposition Da 0 0200 gm Pm yr User s Manual for Phosphorus Prediction Version 1 0 Land Use Category 1 P Export Coefficient E1 0 0069 gm P m yr Model Validation Land Use Category 2 P Export Coefficient E2 0 0625 gm P m yr Land Use Category 3 P Export Coefficient E3 0 0000 gm P m yr
41. bols are the same as for the truncated pyramid formula Volume h 3 x Ay Ar 4 Au x AL 60 Leer Le Manual for Phosphorus Prediction Version 1 0 Lake George Kings County 44 56 64 42 June 1978 030 Chemistry Station 500 Om Figure V 3 Bathymetric map of Lake George obtained from the Nova Scotia Department of Agriculture and Fisheries 61 Leer e Manual for Phosphorus Prediction Version 1 0 V 5 Estimate of Atmospheric Phosphorus Deposition Coefficient Atmospheric phosphorus unit deposition Da was assumed to be 0 020 mg gm m yr the average of the values reported for Nova Scotia see Section 7 1 3 2 V 6 Estimates of Phosphorus Surface Run Off Coefficients Estimates of phosphorus surface run off coefficients were made based on the geology soil types and land use characteristics of the drainage basin Information on bedrock geology was obtained from Donohoe and Grantham 1989 and Finck et al 1994 and soil characteristics were obtained from Cann et al 1965 The bedrock geology is primarily intrusive granite coved by a shallow layer of glacial drift The major soil type in the drainage basin belongs to the Gibraltar series which consists of coarse till There is little evidence that either geology or soil type vary significantly within the drainage basin of Lake George Land use categories include forest 640 4 ha clear cut forest land 52 3 ha wetland 8 3 ha agriculture
42. d decay the phosphorus they contain can be transformed into forms that can be recycled if they remain in the soluble form By far the largest quantity of phosphorus present in aquatic systems is that contained in the non living organic particulate form This is commonly referred to as detrital phosphorus and consists of dead aquatic organisms as well as terrestrial plants and animals that have been washed into the system As this pool of organic matter is metabolized by bacteria and other detritus feeding organisms phosphorus is released and may once again become available to plants to complete the cycle 2 3 Factors Controlling Algal Growth The two major factors that control algal growth in aquatic ecosystems are the availability of light and the availability of nutrients both of which are strongly influenced by the amount of mixing of the water column In stratified systems the depth to which algae are mixed is determined by the thermocline depth Ifthe thermocline depth is shallow the algae will spend most of the time within the upper portion of the water column where there is usually sufficient light for photosynthesis and if nutrients are plentiful will grow rapidly If however the system is unstratified and relatively deep the algae will be mixed throughout the water column and may spend a significant portion of the time in that part of the water column where light levels are too low to support photosynthesis In this case algal gro
43. e loss of phosphorus by settling to sediments is proportional to its concentration in the lake e Seasonal fluctuations in hydraulic and phosphorus loading can be neglected A major difficulty encountered in using Vollenweider s model is that it requires knowing the net sedimentation rate of phosphorus once it enters the lake This has proven to be a 11 Leer Le Manual for Phosphorus Prediction Version 1 0 difficult parameter to measure largely because of the problems involved in separating phosphorus settling from phosphorus resuspension under experimental conditions Based on an analysis of data from 21 temperate zone European and North American lakes Vollenweider 1976 estimated o the phosphorus sedimentation rate to be equal to approximately 10 divided by the mean depth of the lake This formulation however requires that the mean depth of the lake be known which in turn requires a bathymetric survey of the lake A number of studies Larsen and Mercier 1976 Canfield and Bachmann 1980 have shown that lake phosphorus retention is highly correlated with the areal hydraulic load One of the most commonly used formulations for phosphorus retention was developed by Kirchner and Dillon 1975 based on an analysis of Ontario lakes In this formulation the proportion of phosphorus lost to the sediments Rp is estimated as follows Rp v v qs where v apparent settling velocity qs areal hydraulic load In a later study Di
44. e that has effluents entering lakes located downstream If a downstream lake exceeds a phosphorus objective no upstream development would be allowed The retention of phosphorus in streams and rivers can result from settling of particulate phosphorus sorption of dissolved phosphorus to stream sediments chemical precipitation of phosphorus and uptake of phosphorus by benthic algae and macrophytes Wagner et al 1996 Behrendt and Opitz 2000 carried out a number of studies in which it was found that as much as 20 to 40 of the phosphorus load was retained within streams before reaching the receiving water body VI 2 1 3 Proximity of Dwellings to Lake When assessing the impacts of development most phosphorus loading models have only considered dwellings located within 300 m of the lake s shoreline or a tributary entering the lake and that phosphorus export to the lake is not influenced by the distance of the dwelling from the lake The 300 m distance is arbitrary and has never been substantiated Hutchinson 2002 has proposed that this be modified to at least include a factor that takes into consideration the distance of the dwelling from the shoreline of the tributary He proposes that the 300 m limit be maintained but because all soils have some ability to 13 Leer e Manual for Phosphorus Prediction Version 1 0 retain phosphorus the amount of phosphorus export to the lake or tributary be reduced as follows e Developme
45. ed to a water body it refers to its level of biological productivity Three commonly used terms to define the trophic status of a water body are oligotrophic little nourishment mesotrophic moderate nourishment and eutrophic much nourishment Oligotrophic systems are characterized by relatively pristine conditions and low levels of production Eutrophic systems are Leer e Manual for Phosphorus Prediction Version 1 0 characterized by a high biomass of plants especially algae and in many instances low levels of dissolved oxygen which can result in the build up of toxic products such as methane hydrogen sulphide and ammonia Eutrophic conditions can lead to fish kills and species shifts of both plants and animals A fourth trophic term dystrophic literally means abnormal nourishment and is used to describe systems that do not fall into the above categories Dystrophic water bodies are characterized by colored water mostly as a result of receiving run off containing dissolved humic compounds that originate from peatlands or leachates produced from the breakdown of coniferous vegetation within a watershed Because lakes lie in depressions within the land they are natural traps for particulate materials containing nutrients that enter via their inflows As a result all lakes gradually accumulate nutrients and at some point will become eutrophic This natural eutrophication is a slow process on the order of tens of centuries in most cases
46. eous S Sedimentary Mainly roads and open water F Fine gt 15 clay M Medium 5 to 15 clay C Coarse lt 5 clay 23 Leer e Manual for Phosphorus Prediction Version 1 0 In a summary of their results Scott et al 2000 suggest the following general export values e Igneous Forested Watersheds 0 0069 gm m yr e Igneous Forested Watersheds with gt 15 cleared wetland 0 0083 gm m yr e Sedimentary Forested Watersheds 0 0088 gm m yr e Sedimentary Forested Watersheds with gt 5 cleared wetland 0 0115 gm m yr Lowe 2002 carried out a similar study for a number of stream catchments located in the Gaspereau River watershed The estimated phosphorus export coefficients Table 7 3 are considerably higher than those reported by Scott et al 2000 The difference may be related to the highly colored waters typical of the lower reaches of the Gaspereau watershed where the study was carried out Table 7 3 Phosphorus export coefficients measured by Lowe 2002 for watersheds located in the Gaspereau River system Kings County Nova Scotia Land Use Phosphorus Geology Soil Type Export Forest Clearcut Wetland Agriculture gm m yr Igneous Coarse 99 0 1 0 0 0327 Igneous Coarse 85 15 0 0 0 0634 Igneous Medium Coarse 80 14 0 6 0 0304 Sedimentary Medium Fine 79 3 0 18 0 0354 Sedimentary Medium Fine 80 4 0 16 0 040
47. eristics and particularly with respect to inputs of phosphorus resulting from human activities The intended users of the manual include federal and provincial resource management agencies provincial regulatory officers municipal planners consulting agencies and non governmental organizations and individuals The general approach presented here has previously been applied within Nova Scotia for lakes associated with the Gaspereau River watershed Horner Associates Ltd 1995 Shubenacadie River watershed Hart et al 1978 Nine Mile River watershed Dillon Consulting Ltd 2003 a Cape Breton highlands lake Kerekes 1983 and numerous lakes in the Halifax area Soil and Water Conservation Society of Metro Halifax 1992 1993 Leer e Manual for Phosphorus Prediction Version 1 0 Scott et al 2003 carried out a study comparing these models and concluded that all of the models were essentially the same in terms of their general formulations and assumptions 2 Some Basic Limnological Concepts Anyone who attempts to use the model presented in this manual to predict the phosphorus concentration of a lake or to determine the permissible loading of phosphorus to a lake should have at least a general knowledge of the factors that cause eutrophication as well as of the processes that determine the degree to which a particular lake is subject to becoming eutrophic Of particular importance is an understanding of how phosphorus cycles within a l
48. export coefficients and simply removing the development contribution of phosphorus to determine the pre development lake phosphorus concentration He stresses however that the model must be well developed and validated if the results are to be of any significance 79 Leer e Manual for Phosphorus Prediction Version 1 0 VI 5 References Behrendt H and D Opitz 2000 Retention of nutrients in river systems dependence on specific runoff and hydraulic load Hydrobiologia 410 111 122 Chapra S C 1975 Comment on An empirical method of estimating the retention of phosphorus in lakes by W B Kirchner and P J Dillon Wat Resourc Res 11 8 1033 1034 Chapra S C 1997 Surface water quality modeling McGraw Hill New York Chow Fraser P and H C Duthie 1987 Response of the phytoplankton community to weekly additions of ammonium phosphate in a dystrophic lake Archiv fur Hydrobiologia 110 67 82 Dillon P J and L A Molot 1997 Effect of landscape form on export of dissolved organic carbon iron and phosphorus from forested stream catchments Water Resour Res 33 2591 2600 Environment Canada 2003 Canadian guidance framework for the management of phosphorus in freshwater systems National Guidelines and Standards Office Water Policy and Coordination Directorate Gatineau Quebec 116 p Faulkner S P and C J Richardson 1989 Physical and chemical characteristics of freshwater wetland soils p 41 72 Jn
49. ficients than those with colder dryer climates e The amount intensity and duration of precipitation have a large influence on phosphorus export coefficients Geology and Soil Types e Sandy soils overlying granitic igneous formations tend to have high nutrient export e Loamy soils contain more nutrients and are more subject to erosion than sandy and gravely soils and tend to have higher export coefficients e Clay soils are highly erosive have poor water infiltration and a high capacity to adsorb phosphorus which results in high export 21 Leer e Manual for Phosphorus Prediction Version 1 0 e Organic soils have high nutrient contents poor infiltration capacity limited phosphorus retention capacity and high export Forestry e Relative to other land uses phosphorus export from forests is generally low on the order of 0 001 to 0 015 gm m yr e Forested watersheds with sandy soils overlying granitic igneous formations export about one half the phosphorus than do forested watersheds with loamy soils overlying sedimentary formations e Deforested watersheds have high export of phosphorus e Young lt 5 years old forests have relatively high phosphorus export Cultivated Lands e Phosphorus export from cultivated lands tends to be very high and variable e Heavily fertilized or manured lands particularly if over fertilized have high phosphorus export but this is reduced considerably if the fertilizer or manure is worked i
50. fied and the bottom waters may become anoxic Ice Cover Spring Overturn Summer Stratification Fall Overturn Ice Cover Figure 2 2 A temperature isopleth illustrating the seasonal development of stratification in a lake The dashed line represents the position of the thermocline Modified from Wetzel 1983 2 2 The Aquatic Phosphorus Cycle The cycling of phosphorus in aquatic ecosystems is complex and involves physical chemical and biological transformations Figure 2 3 The major source of natural phosphorus is through weathering and erosion of rocks where phosphorus exists in a relatively insoluble oxidized form complexed with metals such as aluminium iron and magnesium The resistance of these compounds to dissolution is one of the reasons why phosphorus is so often limiting in aquatic ecosystems Once phosphorus enters a water body it has numerous fates If it exists as an insoluble precipitate it may settle to the bottom where it becomes buried within the sediments with little chance of being returned to the water column This is typically the case in an unproductive well oxygenated lake If however the lake is a productive one and it Leer e Manual for Phosphorus Prediction Version 1 0 contains an anoxic zone either at the sediment surface or within the bottom water layer the precipitate may be chemically transformed to a reduced state which is soluble and biologically av
51. freshwater resources to provide clean water for industrial domestic agricultural and recreational purposes has raised concerns about the kind and amount of development that can be tolerated in watersheds containing these resources In many areas of the world freshwater systems have been severely degraded as a result of poor watershed management and lack of land use planning Although Nova Scotia contains many relatively pristine watersheds concern about threats to the quality of our freshwater resources from increased development and the land use changes that accompany development has been raised in the past Waller 1971 and many believe that it is now time to develop procedures for determining the kind and level of development that can be endured within Nova Scotia watersheds before water quality becomes impaired Over the last three decades considerable effort has been extended by many agencies to develop a simple procedure that can be used to determine the extent to which a watershed can be altered before the aquatic ecosystems it contains begin to exhibit impaired water quality as a result of excessive nutrient enrichment In North America many provinces and states are in the process of developing nutrient criteria designed to protect freshwater systems from nutrient overenrichment Of major concern is human activity that results in alterations of the tropic status of lakes The term trophic literally means nourish and when appli
52. g of agencies that can be contacted to obtain maps and other data required to estimate model parameters Table 7 1 Model inputs Morphological Parameters Symbol Units Drainage Basin Area exclusive of lake Ad m Surface Area of Each Land Use Category Adi m Lake Surface Area Ao m Lake Volume V m Hydraulic Input Parameters Upstream Hydraulic Inputs Qi m yr Annual Unit Precipitation Pr m vr Annual Unit Lake Evaporation Ev m yr Annual Unit Hydraulic Run Off Ru myr Phosphorus Input Parameters Upstream Phosphorus Input Ji gm yr Annual Unit Atmospheric Phosphorus Deposition D gm m yr Annual Unit Phosphorus Export from Land Ei gm m yr Number of Dwellings Na Average Number of Persons per Dwelling Nu Average Fraction of Year Dwellings Occupied Npc yr Phosphorus Input per Capita Year Si gm capita yr Septic System Retention Coefficient Rsp Point Source Phosphorus Inputs PSi gm yr Lake Phosphorus Retention Coefficient v A separate estimate is required for each combination of geology soil type and land use present in the drainage basin 7 1 1 Morphology 7 1 1 1 Drainage Basin Area Ad Estimation of the drainage basin area requires using a topographic map typically at scales of 1 10 000 or 1 50 000 to define the watershed boundary The watershed boundary is the area between the highest points of land and the outlet
53. g organic acids The organic acids are largely in the form of humic and fulvic acids that arise from run off originating in wetlands and forested landscapes dominated by coniferous vegetation Application of nutrient loading models to colored lakes has not been very successful as model predictions of phosphorus concentration are generally much lower than measured lake phosphorus concentrations Kerekes 1981 In addition the relationship between phosphorus concentration phytoplankton production phytoplankton biomass chlorophyll a concentration and Secchi Disk depth appears to be different for colored lakes Jackson and Hecky 1980 Chow Fraser and Duthie 1987 Nurnberg 1996 At present it does not appear that phosphorus loading models as they are presently developed can be as easily applied to reservoirs as they can to natural lakes Kerekes 1982 Kennedy 1998 The major reasons for this are as follows e The depth and volume of reservoirs typically undergo changes over a relatively short term depending on the need for the water they contain As a result the flushing rate and in turn the sedimentation rate of phosphorus varies greatly over the same time period 76 Leer e Manual for Phosphorus Prediction Version 1 0 e Reservoirs used for power generation have their outflows located at the bottom which depletes the hypolimnion and the phosphorus that has settled into it e Reservoirs are often constructed in drowned river valleys a
54. gm yr Total Surface Run Off P Input Total Development P Input 26426 gm yr Total P Input 145582 gm yr Lake P Retention Factor 0 58 n a Lake Phosphorus Retention 84438 gm yr Lake Phosphorus Concentration mg LU Lake Phosphorus Outflow 81144 gm yr Lake Mean Depth 4 6 m Lake Flushing Rate 1 11 times vr Lake Turnover Time 0 90 yr Lake Response Time 0 21 yr 65 Leer e Manual for Phosphorus Prediction Version 1 0 V 10 Model Validation Model validation involves comparing the model s predicted phosphorus concentration with phosphorus concentrations obtained from field measurements Figure V 4 shows the seasonal and yearly variation in phosphorus concentration for Lake George based on measurements made as part of a volunteer based water quality monitoring program coordinated by the Municipality of Kings County The mean value of all of the measurements is 0 0105 mg L REE Oe rrr TT cull 1997 1998 1999 2000 2001 2002 Year Figure V 4 Phosphorous concentration validation data for Lake George The model under predicts the lake s phosphorus concentration by 21 9 which is above the 20 difference generally considered acceptable for model validation see Section 9 of the User s Manual As a result it was decided that the model should be re evaluated 66 Leer e Manual for Phosphorus Prediction V 11 Model Re evaluation Version 1 0 In re evaluation
55. h h osphorus Phosphorus Phosphorus Inflow i Inflow gt Outflow Concentration Outflow Phosphorus Phosphorus Hydraulic Budget Sedimentation Resuspension Phosphorus Budget Figure 3 2 Inputs and outputs of the hydraulic and phosphorus budgets 4 Model Formulation The general equation used to determine the concentration of phosphorus in the lake once the hydraulic and phosphorous inputs are known is based on formulations originally proposed by Bifi 1963 and Piontelli and Tonolli 1964 and further developed by Vollenweider 1968 1975 10 Leer e Manual for Phosphorus Prediction Version 1 0 The Vollenweider model assumes that the change in the amount of phosphorus in the lake over time is equal to the amount of phosphorus entering the lake minus the amount of phosphorus lost to the sediments and the outflow APV At M PV x Q V o xP where PV Total mass of phosphorus in lake gm P Lake phosphorus concentration gm m V Lake volume m t time M Annual mass of phosphorus input to lake gm yr Q Annual volume of water outflow from lake m yr o Sedimentation coefficient wer The steady state solution 1 e setting APV At 0 to this equation is M V Py _ Q V o The major assumptions of the model are e Phosphorus entering the lake is mixed throughout the lake e The concentration of phosphorus in the outflow is equal to the concentration in the lake e Th
56. h the number of years required is debatable most believe that it should be somewhere between five and ten years Hutchinson 2002 provides a number of suggestions for the design of monitoring programs in instances when limited resources are available He suggests that at minimum the following data should be collected e An annual spring overturn measurement of total phosphorus e Biweekly measurements of Secchi Disk depth during the summer e An annual determination of a dissolved oxygen profile at the end of the summer and prior to fall turnover It would also be wise to collect water samples for determination of chlorophyll a concentrations on at least a bimonthly basis 9 1 Protocol for Collection of Validation Data The Nova Scotia Department of Environment and Labour 1999 has produced a manual that provides details of the protocols for collecting water samples for validation data This criteria however may be difficult to meet for lakes having phosphorus concentrations near to the limit of analytical detection 37 Leer e Manual for Phosphorus Prediction Version 1 0 Although the manual was specifically developed for a volunteer water quality monitoring program carried out in Kings County of the Annapolis Valley the protocols described are generic and applicable to any water quality monitoring program This manual should be consulted in designing the validation data sampling program The manual assumes that the
57. iction Version 1 0 Aquaculture Operations Inland aquaculture operations are also potential point sources of phosphorus Within Nova Scotia salmonid aquaculture is most common The amount of phosphorus exported depends mainly on the type and amount of food used For salmonids current operations use high nutrient dense feeds which contain about 1 phosphorus by weight of which approximately one third is assimilated by the fish and two thirds is exported in the effluent personal communication J Blanchard Nova Scotia Department of Agriculture and Fisheries It is therefore possible to estimate the total amount of phosphorus exported based on the amount of food used 7 1 3 6 Lake Phosphorus Retention Coefficient v The amount of phosphorus retained within the lake as a result of phosphorus settling to the sediments requires an estimate of the phosphorus retention coefficient see Section 4 for the coefficients developed by Dillon et al 1986 29 Leer e Manual for Phosphorus Prediction 7 2 Model Outputs The outputs of the model are listed in Table 7 6 Table 7 6 Model outputs Parameter Symbol Units Total Precipitation Hydraulic Input Ppti mi yr Total Evaporation Hydraulic Loss Eo mi yr Total Hydraulic Surface Run Off Q m yr Total Hydraulic Input Qt m yr Areal Hydraulic Load qs m yr Total Hydraulic Outflow Qo m yr Atmospheric Phosphorus Input Jd gm yr
58. in the water column of the lake and Secchi Disk depth a measure of the lake s water clarity Table 1 contains an example of one set of guidelines commonly employed to determine the trophic status of a lake Table 1 Total phosphorus chlorophyll a and Secchi Disk depth boundary values for determining a lake s trophic state Vollenweider and Kerekes 1982 TP Mean Max Mean Secchi Min Secchi Trophic Category ug L Chlorophyll Chlorophyll Depth Depth mg m mg m m m Ultra oligotrophic lt 4 lt 1 lt 2 5 gt 12 gt 6 Oligotrophic lt 10 lt 2 5 lt 8 gt 6 gt 3 Mesotrophic 10 35 2 5 8 8 25 6 3 3 1 5 Eutrophic 35 100 8 25 25 75 3 1 5 1 5 0 7 Hyper eutrophic gt 100 gt 25 gt 75 lt 1 5 lt 0 7 Explanation of terms TP mean annual in lake total phosphorus concentration Mean Chlorophyll mean annual chlorophyll a concentration in surface waters Max Chlorophyll peak annual chlorophyll a concentration in surface waters Mean Secchi Depth mean annual Secchi Disk depth Min Secchi Depth minimum annual Secchi Disk depth The purpose of this manual is to document a procedure that can be used to predict the amount of phosphorus that a lake will contain based on its morphological hydrological and drainage basin characteristics This information can then in turn be used to assess its susceptibility to eutrophication as a result of modifications of any of these charact
59. ir trophic response to phosphorus The former is unlikely to be practical because of the effort and cost that would be involved The latter approach requires the development re Leer e Manual for Phosphorus Prediction Version 1 0 of some sort of lake classification system based on how a lake responds to additions of phosphorus This approach often referred to as the ecoregional or reference condition approach is currently being taken by many federal and state agencies in the United States USEPA 2000 and has been suggested as a potential approach for setting phosphorus objectives in Canada Environment Canada 2003 Determining exactly which factors should be considered in classifying lakes for this purpose is still a subject of debate In general they are those factors that determine the degree to which a lake will respond to an increase in phosphorus concentration and particularly those factors that determine the biomass of algae under conditions when nutrients are not limiting These include those factors that determine the potential level of algal production especially the relationship of lake mixing depth to euphotic zone depth both of which are closely related to the lake s morphology and those factors that determine the loss of algal biomass The later include grazing by zooplankton and flushing from the lake The establishment of phosphorus water quality objectives also requires a somewhat subjective assessmen
60. kes Water Poll Res J Can 20 1 89 105 Underwood J K 1984 An analysis of the chemistry of precipitation in Nova Scotia 1977 1980 Ph D Thesis Technical University of Nova Scotia Halifax Nova Scotia 264 p Uttomark P D J D Chapin and K M Green 1974 Estimating nutrient loading of lakes from non point sources Report No 660 13 74 020 Ecological Research Series United States Environmental Protection Agency Corvallis Oregon Vollenweider R A 1968 The scientific basis of lake and stream eutrophication with particular reference to phosphorus and nitrogen as eutrophication factors OECD Tech Report DAS CSI 68 21 Paris Vollenweider R A 1975 Input output models with special reference to the phosphorus loading concept in limnology Schweiz Z Hydrol 37 53 84 45 Leer e Manual for Phosphorus Prediction Version 1 0 Vollenweider R A 1976 Advances in defining critical loading levels for phosphorus in lake eutrophication Mem Ist Ital Idrobiol 33 53 83 Vollenweider R A and J J Kerekes 1980 Background and summary results of the OECD cooperative program on eutrophication Restoration of lakes and inland waters United States Environmental Protection Agency Report EPA 440 5 81 010 Washington D C Vollenweider R A and J J Kerekes 1982 Eutrophication of waters Monitoring assessment and control Organization for Economic Co operation and Development Paris 156 p Waller D H 1971 Cultural
61. llon et al 1994 they suggested the use of different values of v depending on whether the lake contained an oxic or anoxic hypolimnion 12 4 for the former and 7 2 for the latter Incorporation of this equation into the Vollenweider steady state equation results in the following equation for lake phosphorus concentration note that this formulation does not require that the mean depth or volume of the lake be known M x 1 Rp Q Kalff 2002 provides an excellent discussion of the derivation of this and other variations of the Vollenweider formulation 12 Leer e Manual for Phosphorus Prediction Version 1 0 The general model formulations presented above have been widely used and applied successfully to numerous lakes Sas 1989 Dillon and Rigler 1975 were the first to incorporate these formulations into what is commonly referred to as an export coefficient model where the phosphorus loadings are estimated using phosphorus export coefficients for the various land use characteristics of a lake s drainage basin There are however certain types of lakes for which these formulations do not appear to work well Kalff 2002 These include colored lakes having high concentrations of humic substances lakes that have a low nitrogen to phosphorous ratio and are more likely to be limited by nitrogen rather than phosphorus lakes that have high turbidity and are more likely to be limited by light than nutrients and lakes that are ve
62. meters associated with each of these categories is summarized in Table 7 1 A number of model inputs require estimation of surface areas Examples include the surface area of the lake the surface area of the lake s drainage basin and the surface areas of soil geology and land use types within the drainage basin In the past surface areas have typically been measured using a planimeter There are however other ways to estimate surface areas One of the best and often most precise are those that use Geographic Information System GIS databases containing digital elevations and land use characteristics These are often available through Municipal and Provincial planning agencies Ifa GIS database is not available it will be necessary to obtain maps containing the necessary information and to estimate areas using planimetry There are also a number of image analysis programs that can be used to estimate surface areas They require a digital image of the area to be estimated which may be available from the same agencies that have GIS databases or which can be obtained by digital scanning of an aerial photographs or maps One potential disadvantage is that the scale of the image may be too small to obtain accurate results if the watershed or lake is large Wetzel and Likens 1991 is an excellent source of information on planimetric procedures 15 Leer e Manual for Phosphorus Prediction Version 1 0 Appendix II contains a listin
63. n iron and phosphorus from forested stream catchments Water Resour Res 33 2591 2600 Dillon P J K H Nicholls WA Scheider N D Yan and D S Jefferies 1986 Lakeshore capacity study trophic status Ontario Min Municip Affairs Res and Spec Proj Branch 89 p 41 Leer e Manual for Phosphorus Prediction Version 1 0 Dillon P J and F H Rigler 1974 A test of a nutrient budget model predicting the phosphorus concentration in lake water J Fish Res Board Can 31 1771 1778 Dillon P J and F H Rigler 1975 A simple method for predicting the capacity of a lake for development based on lake trophic status J Fish Res Bd Canada 31 11 1711 1778 Dillon P J W A Scheider R A reid and D S Jeffries 1994 Lakeshore capacity study Part I Test of effects of shoreline development on the trophic status of lakes Lake and Reserv Manage 8 2 121 129 Hart W C 1978 Major ions in Nova Scotia precipitation Ph D Thesis Dalhousie University Halifax Nova Scotia Hart W C R S Scott and J G Ogden HI 1978 A phosphorus loading model for lakes in the Shubenacadie headwaters Technical Report No 2 Prepared for the Shubenacadie Stewiacke River Basin Board Dalhousie University Halifax Nova Scotia 34 p Horne A J and C R Goldman 1994 Limnology 2 ed McGraw Hill New York Horner Associates Ltd 1995 Lake carrying capacities and proposed shoreline development policies Report Prepared fo
64. nd tend to be morphologically more like rivers than lakes e The watersheds of reservoirs are generally much larger than those of lakes and tend to have more surface run off relative to the volume of the reservoir e Because of their larger watersheds reservoirs tend to have higher sediment loads and a greater proportion of their phosphorus input in particulate form Kennedy 1998 makes the following recommendations for anyone attempting to develop phosphorus loading models for reservoirs e Because reservoirs tend to have short hydraulic residence times it may be necessary to formulate nutrient and water balances on a seasonal as opposed to annual basis e Ifthe sediment load is high the phosphorus sedimentation factor should be adjusted e Because of the river like morphology of reservoirs and the tendency for phosphorus to settle near inlets it may be necessary to model reservoirs as a series of longitudinal segments Kerekes 1982 provides an example of how this approach can be applied VI 4 Application of Model to Establishing Phosphorus Water Quality Objectives The trophic response of a lake to inputs of phosphorus depends on many factors and it is unlikely that a single phosphorus water quality objective can be established that would be applicable to all Nova Scotia lakes This makes it necessary to either develop objectives on an individual lake basis or develop objectives for lakes that behave similarly in terms of the
65. nge in its loading of a substance Because this is a logarithmetic function response time is usually expressed as the time for half the change to take place 48 Leer e Manual for Phosphorus Prediction Version 1 0 Secchi Disk A circular disk typically 20 cm in diameter and divided into white and black quadrants used to measure the transparency of a water body Thermocline The area of a stratified lake in which a strong gradient in temperature exists It is often further defined as the area of the lake having a change in temperature of at least 1 C per metre of depth Trophic State An indication of the relative productivity of an ecosystem For freshwater systems it is typically evaluated in terms of the chlorophyll a concentration a measure of algal biomass and the Secchi Disk depth a measure of water transparency Turnover Time The average amount of time that water remains in a lake It is calculated as the ratio of the volume of the lake to the volume of water leaving the lake usually on an annual basis Watershed See Drainage Basin Zooplankton Animals usually microscopic that live suspended within the water column 49 Leer Le Manual for Phosphorus Prediction Version 1 0 15 APPENDICES 50 Leer e Manual for Phosphorus Prediction Appendix I Sample Excel Worksheet Lake Name Version 1 0 Input Parameters Symbol Value Budgets Morphology Drainage Basin Area
66. nt between 100 and 200 m be reduced by one third e Development between 200 and 300 m be reduced by two thirds e Development beyond 300 m considered to have no input VI 2 1 4 Wetlands There are conflicting reports of the amount of phosphorus contributed by wetlands At one extreme some report that wetlands act neither as sources or sinks of phosphorus and that on an annual basis do not have a net export of phosphorus Uttomark et al 1974 Lee et al 1980 Scott et al 2002 on the other hand suggest that wetlands export high amounts of organic rich phosphates Rast and Lee 1980 however suggest that much of the phosphorus exported from wetlands may not be in a form available to algae The results of other studies indicate that wetlands have variable export or retention of phosphorus depending on their flushing rates and the sorptive capacity of the soils contained in the wetland which decreases with time as wetlands age Faulkner and Richardson 1989 Knight et al 1987 advocate that retention is minimal if the residence time of water in the wetland is less than 10 to 15 days Soil sorptive capacity is much more variable and requires empirical data to estimate Dillon and Molot 1997 made estimates of phosphorus loadings for wetlands located in south central Ontario and presented the following relationship Pw Ad x 3 05 0 54 x wetland where Pw Wetland Phosphorus Load kg yr Ad Drainage Basin Area km Wetland
67. nto the soil shortly after application e Pasture and grazing land if overgrazed or fertilized export high amounts of nutrients e Feedlots especially if uncovered and exposed to precipitation have high phosphorus export Urbanization e Urban run off tends to export high amounts of phosphorus and since it is often channelled into storm drains may contain discharges originating from more than one watershed Because export coefficients vary depending on a multitude of factors unless they have been measured in the watershed being modeled the choice of the most appropriate export coefficient to use remains somewhat subjective It is very important to attempt to match climate geology soil and vegetation type as closely as possible when estimates are based on studies that have been carried out in other areas 22 Leer Le Manual for Phosphorus Prediction Land Use Export Coefficients Measured in Nova Scotia Version 1 0 There have been a few studies carried out in Nova Scotia to determine phosphorous export coefficients from various combinations of geology soil type and land use Scott et al 2000 carried out the most extensive study The results are listed in Table 7 2 Table 7 2 Phosphorus export coefficients measured by Scott et al 2000 for various Nova Scotia watersheds Land Use ie Sy Si 5 55 gs Wate
68. o provided much of the information required for the example of the application of the model to Lake George and to Rick Scott and Jonathan Lowe for providing reports and data on phosphorus export coefficients measured in Nova Scotia 40 Leer e Manual for Phosphorus Prediction Version 1 0 13 References Biffi F 1963 Determining the time factor as a characteristic trait in the self purifying power of Lago d Orta in relation to a continual pollution Atti Ist Ven Sci Lettl Atri 121 131 136 Brimley W A D C Ambler R J Porter H T Doane and C L Lin 1985 Hydrologic Network Review Nova Scotia Joint Report by Environment Canada and the Nova Scotia Department of the Environment Canfield D E and R W Bachmann 1980 Prediction of total phosphorus concentrations chlorophyll a and secchi depths in natural and artificial lakes Can J Fish Aquat Sci 38 414 423 Chambers P A M Guy E S Roberts M N Charlton R Kent C Gagnon G Grove and N Foster 2001 Nutrients and their impact on the Canadian environment Agriculture and Agri Food Canada Environment Canada Fisheries and Oceans Canada Health Canada and Natural Resources Canada 241 p Dillon Consulting Limited 2003 Halifax Regional Municipality Nine Mile River Assimilation Study Final Report Dillon Consulting Limited Halifax Nova Scotia 66 p Dillon P J and L A Molot 1997 Effect of landscape form on export of dissolved organic carbo
69. ocated in close proximity to the shoreline of the lake 71 Leer e Manual for Phosphorus Prediction Version 1 0 Related to this is the influence of drainage basin size on phosphorus transport The model assumes that the transport of phosphorus is a linear function of drainage basin area Prairie and Kalff 1986 have evaluated this assumption using literature data tabulated on phosphorus export from 210 drainage basins having a diversity of land uses that included forested and agricultural lands The latter included pasture row crops non row crops and mixed agriculture Their results indicated that drainage basin size does not appear to have an affect on phosphorus export for forested mixed agricultural and non row crops but does for pastures and row crops They suggest that the differences in observed export may be related to the form of phosphorus that is exported from the different land use areas and that particulate phosphorus is for a number of reasons more likely to be retained within the drainage basin than dissolved phosphorus In their study the range and mean percent of particulate phosphorus exported from agricultural land was 44 98 and 84 5 percent respectively For forest lands less than 50 percent of the phosphorus exported was in the particulate form The authors provided the following equations to estimate the relationship between phosphorus export and drainage basin area for pasture and row crop agricultural land
70. of inherent simplifications and assumptions and these must be fully appreciated and understood in order to avoid application of the model to situations in which it has not been shown to work successfully The major purpose of this supplementary document is to discuss these limitations and assumptions to the extent they have been discussed and recorded in the literature so that users of the manual will be able to determine the degree to which the model is applicable to the systems they propose to model A secondary objective of this document is to present some approaches that have been suggested and in some cases applied to overcome some of these assumptions and limitations and should prove particularly useful as a reference in those cases when it proves difficult to validate a model There is also a discussion of the potential for use of the model as an aid to the development of a Phosphorus Water Quality Objective VI 2 Model Assumptions VI 2 1 Phosphorus Transport VI 2 1 1 Drainage Basin Size and Juxtaposition of Land Use Types A major assumption of the model is that the amount of phosphorus transported by surface run off to the lake is independent of the distance over which transport occurs Shuman et al 1975 This means for example that an agricultural land use located in an area of the drainage basin far removed from the lake or tributaries that enter the lake will transport as much phosphorus to the lake as an agricultural area l
71. of the lake This 16 Leer e Manual for Phosphorus Prediction Version 1 0 area is outlined on the topographic map and then by planimetry or some other available method the area of the drainage basin is estimated Use of the largest scale map available that includes the entire drainage basin will provide the most accurate estimates The surface area of the lake should not be included as part of the drainage basin area 7 1 1 2 Surface Area of Each Land Use Category Adi If the drainage basin of the lake contains more than one type of land use and or varies in geology and soil type it will be necessary to estimate the surface area of each combination of land use and soil type since these are likely to differ in their phosphorus export coefficients 7 1 1 3 Lake Surface Area Ao The surface area of the lake is determined by planimetry using either aerial photographs topographic maps or GIS databases In some cases this and other lake morphological characteristics can be obtained from the Nova Scotia Department of Agriculture and Fisheries Lake Survey database The Province has surveyed almost 2000 lakes in Nova Scotia and this information is readily available If the lake contains islands the surface area of the islands should not be included as part of the lake s surface area but should be included as part of the lake s drainage basin 7 1 1 4 Lake Volume V Although the volume of the lake is not in most cases req
72. on Ps 62722 gm yr Lake Phosphorus Concentration mg L Lake Phosphorus Outflow Jo 86615 gm vr Lake Mean Depth Zz 4 6 m Lake Flushing Rate FR 1 11 times yr Lake Turnover Time TT 0 9 yr Lake Response Time 0 21 yr 68 Leer e Manual for Phosphorus Prediction Version 1 0 V 12 Examples of Model Application Having verified the model it can now be used to assess the impact of a particular activity with respect to how it will influence the lake s phosphorus concentration Three examples are presented You may want to make these changes on the Excel spreadsheet to verify the results for yourself 1 What would be the effect of doubling the amount of clear cut forest To evaluate this land use change it is necessary to adjust the areas of the natural forest and clear cut forest in the spreadsheet Increasing the area of the clear cut from 52 3 to 104 6 ha and decreasing the area of the natural forest from 635 4 to 583 1 ha results in a change in phosphorus concentration from 0 0084 to 0 0100 mg L an increase of 19 3 2 What would be the effect of doubling the number of dwellings Doubling the number of cottages to 220 as well as the area of the cottage lots from 43 6 to 87 2 ha which also requires decreasing the area of forestland by 43 6 ha results in changing the phosphorus concentration from 0 0084 to 0 0106 mg L an increa
73. on in phosphorus retention Long narrow water bodies of the type commonly associated with river impoundments for example may have a horizontal gradient in hydrological characteristics resulting in a greater amount of phosphorus retention in the upper portion where influents enter Some lakes also contain more than one basin and these may behave differently from each other In this case it may become necessary to treat each basin as a separate lake especially if there are major differences in the number and characteristics of any tributaries that may enter each basin 75 Leer e Manual for Phosphorus Prediction Version 1 0 VI 3 Model Limitations The model does not appear to work well for lakes that are very shallow Shallow lakes are often characterized by high flushing rates and a limited ability to retain phosphorus Any phosphorus that does settle appears to be easily resuspended as a result of the lake s water column being mixed to depths at or near the sediment surface Welch and Cooke 1995 As a result the model tends to overestimate the retention of phosphorus in shallow lakes Hutchinson 2002 The presence of macrophytes which are often well developed in shallow lakes is also thought to influence the cycling of phosphorus since they can act as pumps bringing nutrients that have been deposited into the sediments back up into the water column Colored lakes are those lakes characterized by high levels of naturally occurrin
74. onal Climatology Coefficients Concentration Watershed Land Use Categories Watershed Geology Watershed Soil Types Watershed Development Construct and Run Model Sensitivity 7 Validate Model Cro Accept Model Make Predictions Compare to Water Quality Objective Identify and Evaluate Management Strategies Re evaluate Model Inputs Figure 4 3 Model development and application procedure Data assimilated from existing literature and other sources is compiled and used to provide the necessary inputs for the model The model is validated by comparing its prediction of the lake s total phosphorus concentration with field measurements see Section 9 If the model prediction and field data agree the model is considered to be validated and can then be used to determine how changes in the model s input parameters 14 Leer e Manual for Phosphorus Prediction Version 1 0 will affect the lake s total phosphorus concentration If the model prediction and field data do not agree it will be necessary to review and re evaluate the data used to estimate the model inputs In the latter case it may prove useful to carry out a sensitivity analysis of each model input see Section 11 7 Model Construction 7 1 Model Inputs The information required to construct the model falls into three general categories 1 drainage basin and lake morphology characteristics 2 hydraulic inputs and 3 phosphorous inputs The specific para
75. opment Input 63 V 8 Determination of Phosphorus Retention Coefficient 63 NO Model Prediction of Phosphorus Concentration 64 W AQ Mod l E E 66 V 11 Model Re evaluation et uge KEEEEAEE ENER ENEE EE Een 67 V 12 Examples of Model Application 69 Appendix VI Supplementary Technical Manual Assumptions and Limitations of the Model e guieekt ge eh deg eegen 70 VLI Introduction caccesvecesseandersentertesdedcecen tals aeons 70 VI 2 Model Assumptions saiciicocesxseranniverasssdigaicerensiepaneiarnayees 71 VI 2 1 Phosphorus Transport 71 VI 2 1 1 Drainage Basin Size and Juxtaposition of Land Use TYPES Ee EE EEN 71 VI 2 1 2 Phosphorus Retention in Streams and Rivers 73 VI 2 1 3 Proximity of Dwellings to Lake cece eee 73 Kap E E 74 VI 2 1 5 Groundwater Inputs os lt sciaccssaosnxesenecaneraxesenesseeds 75 VI 2 2 Lake Morphology enee see ste ee eege deen 75 VI3 Model EC lt 0 csiderassestenineeaneedegnideraneeaicabveresseceancse 76 VI 4 Application of Model to Establishing Phosphorus Water Quality ODJECUVES srsporerio titri kE EEEE EEI EEE AREE EEEE Fi 77 Leer Le Manual for Phosphorus Prediction Version 1 0 MES RETCLENCES eier SEENEN GER EENET 80 vi Leer e Manual for Phosphorus Prediction Version 1 0 User s Manual for Prediction of Phosphorus Concentration In Nova Scotia Lakes A Tool for Decision Making Version 1 0 1 Introduction Increasing pressure on our
76. phorus inputs to septic systems range from as low as 300 to as high as 1800 gm P capita year Uttormark 19 74 Reckhow et al 1980 the higher values being for areas where phosphate detergents are used A commonly used estimate in many models is 800 gm P capita yr Dillon et al 1986 The final parameter required to estimate phosphorus input from residential development is a measure of the adsorption capacity Rsp of the soils in which the septic systems are located This depends on factors such as the age of the septic system the frequency of maintenance the physical and chemical characteristics of the soil surrounding the system and the degree to which the system interacts with the water table Hart et al 1978 estimated that septic systems on Halifax and Wolfville soils retained about 50 of the phosphorus input to septic systems In instances where the model is being used to make conservative predictions of the potential long term consequences of residential development the septic system retention coefficient is often assumed to equal zero see e g Horner Associates Ltd 1995 7 1 3 5 Point Source Inputs PSi The previous discussion of phosphorus loading has dealt with non point sources of phosphorus There are a number of potential point sources of phosphorus that also need to be considered Examples include inputs from sewage treatment plants livestock feedlots and aquaculture operations 27 Leer e Manual for Pho
77. r Lake George in addition to the forestland four other land use categories were identified Figure V 2 Se Lake George Land Use Clear Cut A Pe e E SEH e CS s Kai Wetland gege gt Hay Land T Data Sources Domat 2002 Ae phate Property Database Service Nova Scotia and Municipal Relabons Dat Centretnne Civic Point Fite Deppen Municipalty a othe VC County of Kings Figure V 2 Air photo of Lake George drainage basin showing land use categories 58 Leer e Manual for Phosphorus Prediction Version 1 0 V 3 Determination of Hydrological Inputs Outputs The hydrological inputs outputs include upstream inputs run off from the land precipitation onto the lake and evaporation from the lake Since Lake George is a headwater lake it receives no water inputs from upstream lakes so this value Qi is set to zero If it were to receive upstream inputs this value would be set equal to the Total Hydrologic Outflow of the upstream lake Qo The hydraulic input from land run off is determined as the product of the Annual Unit Hydraulic Run Off and the Area of the Drainage Basin The Hydraulic Unit Run Off Ru is estimated at 0 80 metres yr from the isorunoff map contained in Appendix III The Annual Unit Precipitation Pr onto the lake is estimated as 1 21 metres vr from weather records for Kentville Nova Scotia obtained from the Canadian Climate Normals see Appendix II for so
78. r the Municipality of the County of Kings Kings County Nova Scotia 100 p Hutchinson N J 2002 Limnology plumbing and planning Evaluation of nutrient based limits to shoreline development in Precambrian Shield watersheds p 647 680 In R L France ed Handbook of water sensitive planning and design Lewis Publishers Boca Raton Kalff J K 2002 Limnology Prentice Hall New Jersey 42 Leer e Manual for Phosphorus Prediction Version 1 0 Kerekes J 1983 Predicting tropic response to phosphorus in a Cape Breton Island lake Proc N S Inst Sci 33 7 18 Kerekes J 1982 The application of phosphorus load trophic response relationships to reservoirs Canadian Water Resources Journal 7 1 349 354 Kirchner W B and P J Dillon 1975 An empirical model for estimating retention of phosphorus in lakes Water Resour Res 2 182 183 Larsen DP and H T Mercier 1976 Phosphorus retention capacity of lakes J Fish Res Bd Can 33 1742 1750 Likens G E and O L Loucks 1978 Analysis of five North American Lake Ecosystems III Sources loading and fate of nitrogen and phosphorus Verh Internat Verein Limnol 20 568 573 Lowe J S 2001 Revision of the Kings County lake capacity model validation and implications Report prepared for the Municipality of Kings 21p Lowe J S 2002 Overland phosphorus export in the Gaspereau River watershed application to a lake capacity model MSc Thesis Acadia Universit
79. rshed ER E 2 5 SS Sa Location E z v z jg e Ia SES amp 8 CHERCHER 5 2 g wla S S B ed DIE e li l2 l Halifax I C 83 5 0 0 4 6 0 0 4 1 7 1 0 7 0 0166 Halifax I C 88 2 0 0 9 9 0 0 0 0 0 0 1 9 0 0137 Halifax I C 45 0 0 0 0 0 0 0 0 0 0 0 55 0 0 0024 Petit Etang I C 63 7 0 0 26 5 0 0 8 6 0 0 1 2 0 0107 Petit Etang I C 81 5 0 0 18 3 0 0 0 0 0 0 0 2 0 0041 Prospect I M C 76 4 19 5 0 9 1 6 0 0 0 6 1 0 0 0083 Gillisdale I M 97 1 0 6 0 0 2 1 0 0 0 0 0 2 0 0130 Wentworth I M 86 1 7 9 0 5 2 5 0 0 0 8 23 0 0056 Wentworth I M 87 9 8 8 0 9 0 0 0 0 0 1 2 2 0 0041 Wentworth I M 85 2 11 1 0 4 0 0 0 0 0 4 2 9 0 0042 Wentworth S M 85 6 5 6 1 5 5 4 0 0 0 0 1 9 0 0087 Wentworth S M 93 1 1 8 4 8 0 0 0 0 0 0 0 3 0 0072 Wentworth S M 85 9 5 0 1 0 4 5 0 0 0 6 3 0 0 0108 Mount Thom S M 88 8 5 0 0 8 2 8 0 0 0 3 2 4 0 0058 Mount Thom S M 86 7 6 2 0 7 2 8 0 0 0 3 SE 0 0061 Mount Thom S M 79 9 8 9 0 2 6 1 0 0 3 4 1 5 0 0143 Union Centre S M 81 1 5 5 0 5 7 4 0 0 0 7 1 9 0 0073 Union Centre S M 83 7 4 4 0 5 4 3 0 0 0 6 2 1 0 0058 Union Centre S M 83 3 2 4 0 6 3 2 0 0 0 4 2 3 0 0054 Union Centre S M 86 6 4 7 1 0 5 1 0 0 0 5 2 2 0 0058 Mount Thom S M 82 9 6 4 9 5 0 7 0 0 0 0 0 5 0 0116 Mount Thom S M 82 4 6 5 9 0 1 5 0 1 0 0 0 6 0 0104 Mount Thom S M 83 2 5 5 7 1 3 2 0 2 0 0 0 8 0 0126 Mount Thom S M 82 5 10 9 4 4 0 0 0 3 0 0 1 8 0 0061 Mount Thom S M 77 9 16 1 0 2 5 2 0 0 0 3 0 3 0 0195 Streets Ridge S F 80 0 12 1 1 5 3 5 0 0 0 1 2 9 0 0071 I Ign
80. ry shallow and have short residence times i e high flushing rates It should be noted that the time scale for models based on these formulations is one year which means that the models can not be used to determine average lake phosphorus concentrations for time periods shorter than this There are also numerous other assumptions and limitations associated with this model In some cases modifications can be made to the model to deal with these Some of these limitations and possible solutions for dealing with them are discussed in the Supplementary Technical Report contained in Appendix VI 5 Model Format The model is formatted as an Excel workbook and has been designed so that all of the data for a single lake is contained in a separate worksheet Appendix I contains a sample of the format If the lake being modeled is a headwater lake only one worksheet is required If the lake receives inputs from lakes located upstream those lakes will also have to be modeled each as a separate worksheet An exception to this would be if the upstream hydraulic and phosphorus loadings were already known 13 Leer e Manual for Phosphorus Prediction Version 1 0 6 Modeling Procedure Figure 3 4 illustrates the basic steps involved in constructing and applying the model Data Collection System Description Literature Collect Model Validation Lake and Watershed Survey Data Morphology Estimate Export Lake Total Phosphorus Regi
81. s present in the water column of a lake based on its morphological hydrological and drainage basin characteristics This model has proven to be a useful tool in decision making and assessments of the effect of various alterations within a watershed with respect to how they may influence lake phosphorus concentrations The intended users of the manual include federal and provincial resource management agencies provincial regulatory officers municipal planners consulting agencies and non governmental organizations and individuals il Leer e Manual for Phosphorus Prediction Version 1 0 Table of Contents Page UE Are EE 1 2 Some Basic Limnolopical Concepts eege 8 agasbtaee ENKEN NENNEN dee 4 2 1 Lake Stratification EE 4 2 2 The Aquatic Phosphorus Cycle cicisaescsesiagtivaksaebiannivvessenicaieenes 6 2 3 Factors Controlling Algal Growth ssssssssesssssssssseeeerrerrssssssse 8 KREE H A Model Fo orm latio e AA EE Ee AEN 10 3 Mod l EE dees dere Are ge 13 6 Modeling ENEE 4 u rccpeoracuneemonesedeameveonvenaaiiversnenceueousanaumenmadeed 14 7 Model Construction sisiaicscitcaidxaceainassdpai seca aiead ear siaaieadgera ranean 15 Tek Model re EE 15 Tle E ent 16 7 1 1 1 Drainage Basin Area ged ienneisesaandeatetves 16 7 1 1 2 Surface Area of Each Land Use Category 0065 17 K N De VR Ee E 17 TLA Lake TEE 17 E Re E 18 7 1 2 1 Upstream Hydraulic Input 18 7 1 2 2 Annual Unit Precipitation 18 7 1 2
82. se of 26 2 3 What was the lake s phosphorus concentration prior to human activity in the watershed This question can be answered by eliminating all of the land uses from the model that result from human activity This includes agriculture cottage development camp and public beach inputs and setting the area of the forestland to that of the drainage basin minus the wetland area The results is a lake phosphorus concentration of 0 0045 mg L a value that could be used as reference point for what the lake s phosphorus concentration was prior to human activity in the watershed 69 Leer e Manual for Phosphorus Prediction Version 1 0 APPENDIX VI Supplementary Technical Report Assumptions and Limitations of the Model VI 1 Introduction Over the last several decades the use of mathematical models for predictive purposes has become well established in many areas of ecology This is especially true in aquatic ecology and particularly with regard to their use for the prediction of water quality A large number of water quality models varying greatly in sophistication and level of complexity currently exist see e g Jorgenson 1995 Chapra 1997 The major advantage to the use of mathematical models for predictive purposes is that they represent simplifications of natural systems that are difficult or impossible to duplicate experimentally and provide a means whereby experiments can be performed by altering components of
83. sewers and non point inputs such as atmospheric deposition and surface run off from forested and agricultural lands Although direct measurement of phosphorus loading to the lake would provide the most accurate data this is often impractical to do because of the effort and cost involved In addition if the model is to be used to predict how the lake s phosphorus concentration would change as a result of changes in land use it is essential that land use characteristics and the amount of phosphorus run off associated with each land use be incorporated into the model 7 1 3 1 Upstream Phosphorus Input Ju If the lake being modeled is not a headwater lake phosphorus inputs from streams and rivers draining the watersheds and lakes located upstream must also be estimated from either field measurements or model estimates in order to determine the total phosphorus input to the lake 19 Leer e Manual for Phosphorus Prediction Version 1 0 7 1 3 2 Annual Unit Atmospheric Phosphorus Deposition Da Atmospheric deposition includes dry deposition of particulate phosphorus transported by wind to the lake and wet deposition of phosphorus dissolved in the precipitation falling directly onto the lake Estimates of the dryfall portion are often 70 to 90 of the total deposition Likens and Loucks 1978 Sources of phosphorus transported to a lake by atmospheric deposition can originate outside of the lake s watershed Atmospheric deposition
84. sphorus Prediction Version 1 0 Sewage Treatment Plants Sewage treatment plants STP are often the most important point source inputs to water bodies receiving influents from domestic wastes that discharge either into a lake itself or a tributary leading into a lake Although the quality of STP effluents is required to be monitored the amount of phosphorus contained in STP effluents is not always included in the water quality parameters monitored In this case it becomes necessary to estimate the phosphorus loading based on the number of persons the plant services Table 7 5 provides estimates of the effluent phosphorus load for Ontario STPs having various levels of treatment Table 7 5 Total phosphorus load in the final effluent for various levels of wastewater treatment from Chambers et al 2001 based on data contained in OMEE 1993 Treatment P Removal Number of Effluent Load Type Samples gm P capita yr No 9 624 2 Primary Yes 19 273 5 Average 28 386 9 No 46 376 0 Secondary Yes 137 153 3 Average 183 211 7 No 45 284 7 Lagoons Yes 76 73 0 Average 121 153 3 No 2 372 3 Tertiary Yes 33 54 8 Average 35 73 0 Livestock Feedlots Animal feedlots are also usually treated as point sources of phosphorus export Measured export coefficients are very high on the order of 30 gm m yr for intensive operations Rast and Lee 1977 28 Leer e Manual for Phosphorus Pred
85. t 1980 Availability of phosphorus to phytoplankton and its implications for phosphorus management strategies p 250 308 Jn R Loehr C Martin and W Rast eds Phosphorus management strategies for lakes Ann Arbor Science Ann Arbor Michigan Nurnberg G K 1996 Trophic state of clear and colored soft and hardwater lakes with special consideration of nutrients anoxia phytoplankton and fish J Lake Reserv Memt 12 4 432 447 Prairie Y T and J Kalff 1986 Effect of catchment size on phosphorus export Wat Res Bull 22 3 465 470 81 Leer e Manual for Phosphorus Prediction Version 1 0 Scott R S W C Hart and G Patterson 2000 Phosphorus export from stream catchments in Nova Scotia Internal Report No 93 3 DalTech Dalhousie University Halifax Nova Scotia 102 p Schuman G E R G Sponer and R F Piest 1973 Phosphorus losses from four agricultural watersheds on Missouri Valley Loess Soil Sci Soc Amer Proc 37 424 427 Sims J T R R Simard and B C Joern 1998 Phosphorus loss in agricultural drainage Historical perspective and current research J Environ Qual 27 277 293 Uttomark P D J D Chapin and K M Green 1974 Estimating nutrient loading of lakes from non point sources Report No 660 13 74 020 Ecological Research Series United States Environmental Protection Agency Corvallis Oregon USEPA 2000 Nutrient criteria technical guidance manual 1 ed United States Environment
86. t Rsp was assumed to be 0 5 There are no point source inputs to Lake George so PSi is set to zero on the worksheet V 8 Determination of Phosphorus Retention Coefficient The Phosphorus Retention Coefficient v is an empirically derived constant see Section 7 2 2 5 Since there is some evidence based on monitoring of surface and bottom water temperatures that Lake George experiences stratification and possibly anoxic conditions the value of v is chosen to be 7 2 according to the relationships developed by Kichner and Dillon 1975 63 Leer e Manual for Phosphorus Prediction Version 1 0 VO Model Prediction of Phosphorus Concentration The following table is an illustration of the Excel spreadsheet containing all of the data entries for Lake George The model prediction of phosphorus concentration is 0 0082 mg L The phosphorus budget indicates that 19 88 of the total phosphorus input is due to atmospheric deposition 61 97 is due to surface run off and 18 15 is due to development Of the total phosphorus outputs 58 00 is lost to the sediments and 42 00 is lost via the outflow Lake George Initial Model Input Parameters Symbol Value Units Budgets Morphology Hydraulic Budget m Drainage Basin Area Excl of Lake Area Ad 747 8 ha Area Land Use Category 1 Forest Ad 640 4 ha To
87. t of how much of a change in water quality is considered acceptable The two most commonly used characteristics used to assess water quality with respect to trophic status are water clarity and in a stratified lake the degree to which dissolved oxygen levels become depleted in the hypolimnion If these two criteria are to be used in determining the amount of acceptable change in the water quality of a lake then quantitative relationships between these factors and the biomass of algae and between phosphorus concentration and algal biomass must be developed The latter will differ depending on the particular characteristics of the lake and is further argument of the need for a lake classification system In establishing phosphorus objectives it is also important to consider the range in levels of phosphorus that are characteristic of natural lakes not impacted by human activities This also requires that an extensive database be developed using both existing information and by acquiring new information for those lake types that have not been 78 Leer e Manual for Phosphorus Prediction Version 1 0 well studied This approach also requires that data be available on phosphorus concentration for lakes not impacted by human activity Hutchinson 2002 presents a means whereby a phosphorus water quality objective can be set for a lake that has already been subjected to development The approach involves using a validated phosphorus model based on
88. tains islands as does Lake George the area of the islands must be subtracted This information is used to construct a hypsographic curve in which the area of each depth contour is plotted against depth Surface Area sq m HH A GH HM cH oH fi HH MHP e 0 Surface Area at Each Two 1l Metre Depth Contour 2l Depth Surface Area m m Wi i 0 1 447 015 E 4 4 2 1 157 891 A 5 4 4 880 354 8 6l 6 590 589 Al 8 10 259 i i i i H i 9 0 or J E Hypsographic Curve The volume of the lake V is equal to the area under the hypsographic curve This can be determined by counting the number of squares under the curve each square is equal to 250 000 m or by using the following formula which assumes each layer of the lake is shaped like a truncated pyramid Volume h x Ay A1 2 where h depth between contours Ay Surface area of upper contour Au Surface area of lower contour For Lake George the volumes are as follows Volume 0 2 m 2 x 1447015 1157891 2 2 604 906 Volume 2 4 m 2 x 157891 880354 2 2 038 245 Volume 4 6 m 2 x 880354 590589 2 1 470 943 Volume 6 8 m 2 x 590589 10259 2 600 848 Volume 8 9 m 1 x 10259 0 2 5130 Total Volume 6 720 072 m Another method for calculating the volume of a lake is to use the formula for a truncated cone which assumes each layer of the lake is shaped like a truncated cone sym
89. tal Area Land Use Category 2 Clear Cut Ad2 52 3 ha Upstream Inflow 0 0 Area Land Use Category 3 Wetland Ad3 8 3 ha Precipitation 1750991 22 64 Area Land Use Category 4 Hay Land Ad4 3 2 ha Surface Run Off 6066090 77 36 Area Land Use Category 5 Cottage Lots Ad5 43 6 ha Evaporation 260478 3 37 Area Land Use Category 6 Ad6 0 0 ha Total Outflow 7556603 96 63 Area Land Use Category 7 Ad7 0 0 ha Total Check 100 00 Area Land Use Category 8 Ad8 0 0 ha Area Land Use Category 9 Adg 0 0 ha Phosphorus Budget gm yr Area Land Use Category 10 Ad10 0 0 ha Lake Surface Area Ao 144 7 ha Total Lake Volume V 6 72 10 m Upstream Inflow 0 0 Hydrology Atmosphere 28942 19 88 Upstream Hydraulic Inputs Qi 0 mi vr Surface Run Off 90214 61 97 Annual Unit Precipitation Pr 1 21 m yr Development 26426 18 15 Annual Unit Lake Evaporation Ev 0 18 m vr Sedimentation 84438 58 00 Annual Unit Hydraulic Run Off Ru 0 80 m yr Total Outflow 61144 42 00 Phosphorus Inputs Total Check 100 00 Upstream P Input Ju 0 gm Pur Annual Unit Atmospheric P Deposition Da 0 0200 gm P m yr Land Use Category 1 P Export Coefficient E1 0 0069 gm P m yr Model Validation Land Use Category 2 P Export Coefficient E2 0 0625 gm P m yr Land Use Category 3 P Export Coefficient E3 0 0000 gm P m ur Land Use Category 4 P Export Coefficient E4 0 0081 om Pm wl Predicted P mg L 0 0082 Land Use Category 5 P Export Coefficient E5 0 0300 gmPm yr Measured P mg L 0 0105 Land Use
90. tends to be highest in areas surrounding agricultural lands as a result of wind erosion of fertilized soils and within urban areas as a result of the fly ash produced by burning of fossil fuels There have been very few measurements of atmospheric phosphorus deposition for Nova Scotia Studies by Hart 1977 Hart et al 1978 and Thirumurthi and Hart 1985 carried out in the Halifax area and the headwater region of the Shubenacadie River watershed suggest that a value of 0 025 gm m yr is a reasonable estimate for Nova Scotia Lowe 2002 estimated a value of 0 014 gm m yr for the Wolfville area The lower value may be related to differences in the relative degree of urban development Measurements made by Underwood 1984 for various areas in Nova Scotia suggest an average value of about 0 017 gm m yr 7 1 3 3 Annual Unit Phosphorus Export from Land Ei The export of phosphorus from the land is expressed as an export coefficient which is the amount of phosphorus carried into the lake by surface water run off expressed as gm per square metre per year The value of export coefficients vary depending on geology soil type and land use and require analyzing the drainage basin of the lake to determine what combination of these characteristics it possesses Phosphorus export coefficients are often the most difficult model parameter to estimate because of the diversity of climate geology soil type and land use activity that can occ
91. uired to predict the lake s phosphorus concentration it is required for calculation of the lake s mean depth residence time turnover rate and response time see Section 7 2 3 Determining the volume of the lake requires having a bathymetric map that shows the area of the lake at each depth This information is then used to construct a hypsographic 17 Leer e Manual for Phosphorus Prediction Version 1 0 curve which represents the change in surface area with depth The area under the curve is then integrated by planimetry to determine the volume of the lake Alternatively the volume of the lake can be determined using the formula for either a truncated pyramid or truncated cone see Appendix V for an example 7 1 2 Hydrology 7 1 2 1 Upstream Hydraulic Inputs Qi If the lake being modeled is not a headwater lake it will be necessary to determine the hydraulic input from any upstream lakes that flow into the lake Unless this is known from field measurements of stream and river inflows into the lake it will be necessary to estimate the hydraulic input using the same procedures as for the lake being modeled 7 1 2 2 Annual Unit Precipitation Pr An estimate of the total annual precipitation expressed on a square metre basis is required to account for the precipitation input that falls directly onto the lake This information can be obtained from the Canadian Climate Normals see Appendix II Long term averages e g
92. ur in a watershed 20 Leer e Manual for Phosphorus Prediction Version 1 0 The first step is to partition the drainage basin according to its various combinations of geology soil type and land use and determine the area of each partition Maps depicting geology soil type and forest type cover are readily available from various Provincial agencies Land use characteristics are often available from Municipal databases and in many cases are available in GIS formats Recent aerial photography is also a useful resource for delineating land use characteristics It is always a good idea to ground truth the results of any land use interpretations especially if the maps or photos being used are not recent i e more than 3 5 years old Once appropriate maps and photos have been acquired it is necessary to determine the surface area of each land use category along with the underlying soil type and geology The general land use categories most often considered in the development of phosphorus loading models are forest lands cultivated and uncultivated agricultural land wetlands and developed urban and residential lands While there is considerable variation in the amount of phosphorus exported from a given land use category partly as a result of differences in climate soil type and geology some general patterns have emerged Reckhow et al 1980 These are summarized below Climate e Warm climates with high rainfall have higher export coef
93. urce The Canadian Climate Normals is also used to estimate Annual Unit Lake Evaporation Eu of 0 18 metres vr The following is a partial listing of the database obtained from the Canadian Climate Normals website Canadian Climate Normals 1971 2000 Created 2002 06 21 Modified 2003 07 24 Reviewed 2003 07 24 URL http climate weatheroffice ec gc ca climate_normals results_e html The Green Lane Environment Canada s World Wide Web Site NOTE Data used in the calculation of these Normals may be subject to further quality assurance checks This may result in minor changes to some values presented here KENTVILLE CDA NOVA SCOTIA Latitude 45 4 N Longitude 64 28 W Elevation 48 80 m Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Rainfall mm 60 2 45 0 63 9 70 5 92 7 814 87 6 85 5 87 3 93 3 103 7 77 0 948 0 Snowfall cm 70 9 592 45 9 173 3 7 0 0 0 0 0 0 0 0 19 11 9 55 0 265 9 Precipitation mm 126 7 101 5 110 6 90 2 974 814 87 6 85 5 87 3 95 5 1174 129 9 1210 9 Lake Evaporation mm 3 1 3 6 3 9 3 4 25 1 5 18 0 59 Leer Le Manual for Phosphorus Prediction Version 1 0 V 4 Determination of Lake Surface Area and Volume The surface area of the lake Ao as well as the surface areas at selected depth contours is determined from a bathymetric map Figure V 3 using planimetric or image analysis procedures The results for Lake George are shown in the table below It should be noted that if the lake con
94. wth will be limited even though nutrients levels may be quite high Because of the dependency of algal growth on both light and nutrients stratified systems are more susceptible to becoming eutrophic than are unstratified systems unless the lake is relatively shallow and sufficient light is available throughout the water column Leer e Manual for Phosphorus Prediction Version 1 0 3 Model Overview Figure 3 1 is a hierarchical diagram showing the relationships between the major factors that determine the concentration of phosphorus in a lake Climate watershed characteristics and lake morphology are the main determinants and information on all of these factors is required to construct the model Climate and watershed characteristics are the main determinants of the amount of water and phosphorus that enters the lake and the morphological characteristics of the lake determine how much phosphorus remains within the water column of the lake Drainage Basin Area Hvdrauli raulic Geology Precipitation oad Evaporation Soil Type Drainage Basin Characteristics Natural Vegetation Phosphorus So bett Load PEN mospheric osphorus Deposition Load Phosphorus c Concentration Population Load Density Surface Area ei Depth j ay Land Use Anthropogeni ar Phosphorus Phosphorus Lake Sedimentation Lake Volume Flushing Hydraulic Load Rate Figure 3 1 Hierarchical diagram illustrating the major factors controlling
95. y Wolfville Nova Scotia 139p Maine Department of Environmental Protection 2000 Report No DEPLW 112 Final Lakes TDML Report Maine Department of Environmental Protection Lakes Assessment Division Augusta Maine Nova Scotia Department of Environment and Labour 1999 Kings County Nova Scotia Volunteer Lake Water Quality Monitoring Program NSDEL Halifax Nova Scotia 43 Leer e Manual for Phosphorus Prediction Version 1 0 OMEE 1993 Report on the 1991 discharge from municipal sewage treatment plants in Ontario Vol 1 Summary of performance and compliance Ontario Ministry of Environment and Energy Toronto Ontario Piontelli R and V Tonolli 1964 The time of retention of lacustrine waters in relation to the phenomena of enrichment in introduced substances with particular reference to Lago Maggiore Mem Ist Ital Idrobiol 17 247 266 Rast W and G F Lee 1977 Summary analysis of North American U S Portion OECD Eutrophication Project Nutrient loading lake response relationship and trophic status indices Report No EPA 600 3 78 008 Ecological Research Series United States Environmental Protection Agency Corvallis Oregon Reckhow K H 1979 Empirical lake models for phosphorus Development applications limitations and uncertainty p 193 221 Jn D Scavia and A Robertson eds Perspectives in lake ecosystem modeling Ann Arbor Science Publishers Michigan Reckhow K H and S C Chapra 197

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