Minidisk-Infiltrometer-Manual
Contents
1. ionic balance and may flocculate or disperse the clay in the soil upper stopper S suction control tube Fig 2 Filling the upper chamber Mini Disk Infiltrometer 3 Preparation Once the upper chamber is full slide the suction con trol tube all the way down invert the infiltrometer remove the bottom elastomer with the porous disk and fill the water reservoir Fig 3 Removing the bottom elastomer The position of the end of the mariotte tube with respect to the porous disk is carefully set to ensure a zeto suction offset while the tube bubbles If this di mension is changed accidentally the end of the mariotte Mini Disk Infiltrometer 3 Preparation tube should be reset to 6mm from the end of the plas tic water reservoir tube 4 Replace the bottom elastomer making sure the porous disk is firmly in place 5 If the infiltrometer is held vertically no water should leak out Adjustable suction tube Fig 4 Upper chamber and suction tube 10 Mini Disk Infiltrometer 3 Preparation Choosing the Suction Rate Since different soil types will infiltrate water at different rates measuring the change of volume vs time can often L 4 60 1 TP A SECONDS 50 50 be difficult particularly in a sandy soil where the water will infiltrate rapidly Therefore you can adjust the suction rate to better acco2. in the previous chapter Then do the following 1 d Record the starting water volume At time zero place the infiltrometer on the surface assuring that it makes solid contact with the soil sur face Record volume at regular time intervals as the water infiltrates The time interval you choose is based on both the suction rate you select and the soil type being measured For example a sand will typically be 2 5 seconds between readings a silt loam every 30 sec onds and a tight clay 30 to 60 minutes A typical data set will look like the first and third columns of Table 1 For the calculation of hydraulic conductivity to be accutate at least 15 20 mL of water needs to be infil trated into the soil during each measurement Table 1 Sample infiltrometer data Time s sqrt t Volume mL Infiltration cm 0 00 95 0 00 30 5 48 89 0 39 60 7 15 86 0 58 13 Mini Disk Infiltrometer 4 Collecting Data Table 1 Sample infiltrometer data Time s sqrt t pes ST 90 9 49 83 0 77 120 10 95 80 0 97 150 12 25 77 1 16 180 13 42 75 1 29 210 14 49 73 1 42 240 15 49 71 1 55 270 16 43 69 1 68 300 17 32 67 1 81 Use the Spreadsheet Macro Decagon has created a basic Microsoft Excel spreadsheet to help calculate the slope of the curve of the cumulative infiltration vs the square toot of time based on
3. 010 1 23 7 89 8 09 8 51 8 95 9 41 9 90 10 41 loam sandy clay 0 027 1 23 3 34 3 57 4 09 4 68 5 36 6 14 7 04 silty clay 0 005 1 09 6 08 6 17 6 36 6 56 6 76 6 97 7 18 clay 0 008 1 09 4 00 4 10 4 30 4 51 4 74 4 98 5 22 16 Mini Disk Infiltrometer 4 Collecting Data quadratic equation is included in the Excel spreadsheet Columns 2 and 4 from the table are used to produce an XY scatter plot to the right of the table This is used to calculate C which is the slope of this line denoted as y An example is shown in the graph below D o e y 0 0028x 0 0575x R 0 9987 a Cumulative Infiltration cm o a e o e 0 5 10 15 20 Square Root of Time In this example the value of C is 0 0028 cm s The soil is a silt loam so from Table 2 for 2cm suction A 7 93 The hydraulic conductivity at 2 cm suction is therefore k 0 0028 cm s 7 93 3 53 x 104 cm s Occasionally infiltrometer data will give a negative C value Negative hydraulic conductivity is a physical impos sibility so such valves indicate a problem with the data set Usually such data come from shallow flow restricting lay ers of jiggling the infiltrometer during the measurement A much more extensive discussion of tension infiltrome ter measurement and analysis is given in Dane and Topp 2002 p 888 896 17 Mini Disk Infiltr
4. Mini Disk Infiltrometer User s Manual Version 10 DECAGON DEVICES Decagon Devices Inc 2007 2012 All rights reserved Decagon Devices Inc 2365 NE Hopkins Court Pullman WA 99163 Mini Disk Infiltrometer Table of Contents Contents 1 Introduction Wo a i oaa a C RS Welcome 2 satiate d cess d aot Treated area gun dod 1 Customer Support toa vh duci ek tes toc ea 1 SDeCIEICADODS hotes does tee RE es 2 Warranty Information LES eem tx Rr xt 2 Sellers abs as un rente 2 2 The Infiltrometer 4 How it Works x cusa cs ste se RR 4 DAE UTC S s dun Qe erae thee Sos SU eke i oh 5 Hydraulic Conductivity cuero ere erac eats 6 3 Preparation 0000 00 o o o 0 0 0 o 0 0 8 Choosing the Suction Rate 11 Placement as ose dr Doer usar nios eec 12 4 Collecting Data 13 Use the Spreadsheet Macro 14 Calculate AO once tette tes 15 5 Water Repellency Index 19 Mini Disk Infiltrometer Table of Contents 6 Maintenance 000 21 CHCA UNG o o ebielo Pim tds bis ee 21 Suction Tube 2 cuu x m oe meee eaee Nets 21 7 References and Reading 22 BReteteriQes sidi total 22 Additional Reading i us aea n trot 29 INDEX ovre ur wes 20 Mini Disk Infiltrometer 1 Introduction 1 Introduction Welcome Welcome to the Mini Disk Infiltrometer for measuring soil hydraulic conductivity The infiltrometer will enable you to measure the hy
5. draulic conductivity of any soil accurately and affordably Customer Support If you ever need assistance with your Mini Disk Infiltrome tet ot if you just have questions or feedback there are sev eral ways to contact us Customer service representatives are available to speak with you Monday thru Friday between 7am and 5pm Pacific time NOTE If you purchased your Mini Disk Infiltrometer through a distributor please contact them for assistance E mail support decagon com or sales decagon com Phone 1 509 332 5600 Fax 1 509 332 5158 If contacting us by email or fax please include as part of your message your instrument s serial number your name address phone and fax number Mini Disk Infiltrometer 1 Introduction Specifications Total Length 32 7 cm Diameter of tube 3 1 cm Sintered stainless steel disc 4 5cm dia 3 mm thick Length of suction regulation tube 10 2 cm Suction range 0 5 to 7cm of suction Length of water reservoir 21 2 cm Length of Mariotte tube 28cm Volume of water required to operate 135ml Warranty Information The infiltrometer has a 30 day satisfaction guarantee and a one year warranty Seller s Liability Seller warrants new equipment of its own manufacture against defective workmanship and materials for a period of one year from date of receipt of equipment the results of ordinary wear and tear neglect misuse accident and excessive deterioration due to corrosi
6. egulation tube is difficult to move use a small amount of vacuum grease to allow it to move more freely 21 Mini Disk Infiltrometer 7 References and Reading 7 References and Reading References Brady N C and R R Weil 1999 The Nature and Prop erties of Soils Prentice Hall Upper Saddle River New Jetsey Carsel R F and R S Parrish 1988 Developing joint probability distributions of soil water retention characteristics Water Resour Res 24 755 769 Dane J H and G C Topp Eds 2002 Methods of Soil Analysis Part 4 Physical Methods Soil Science Soci ety of America Madison WI Dohnal M J Dusek and T Vogel 2010 Improving hydraulic conductivity estimates from Minidisk Infiltrometer measurements for soils with wide pore size distributions Soil Sci Soc Am J 74 804 811 Hallet PD Baumgartl T Young I M 2001 Subcritical water repellency of aggregates from a range of soil management practices Soil Sci Soc Am J 65 184 190 Kirkham M B 2005 Principles of Soil and Plant Water Rela tions Elsevier Academic Press Burlington MA pp 145 172 22 Mini Disk Infiltrometer 7 References and Reading Lichner L Hallett P D Feeney D Dugova O Sir M Tesar M 2007 Field measurement of soil water repellency and its impact on water flow under dif ferent vegetation Biologia 62 537 541 Rose C W 1966 Agricultural physics Permagon Pr
7. es Ltd Tilman R W Scotter D R Wallis M G Clothier B E 1989 Water repellency and its measurement by using intrinsic sorptivity Aust J Soil Res 27 637 644 Zhang R 1997 Determination of soil sorptivity and hydraulic conductivity from the disk infiltrome ter Soil Sci Soc Am J 61 1024 1030 Additional Reading Clothier B E 2001 Infiltration Soi and Environmental Analysis Edited by Keith A Smith and Chris Mullins 23 Mini Disk Infiltrometer 7 References and Reading 24 Mini Disk Infiltrometer Index Index C Collecting data calculate infiltration 15 using the spreadsheet macro 14 Customer Support 1 E Email 1 F Fax number 1 H How the infiltrometer works 4 Hydraulic conductivity 6 I Infiltrometer how to use 8 M Maintenance cleaning 21 suction tube 21 P Preparation choosing the suction rate 11 placement 12 Probe features 5 25 Mini Disk Infiltrometer Index S Seller s liability 2 Specifications 2 T Telephone number 1 W Warranty 2 26
8. lassroom use in demonstrating basic concepts of soil hydraulic conductivity How it Works The upper and lower chambers of the infiltrometer are both filled with water The top chamber or bubble cham ber controls the suction The lower chamber contains a volume of water that infiltrates into the soil at a rate deter mined by the suction selected in the bubble chamber The lower chamber is labeled like a graduated cylinder with volume shown in mL The bottom of the infiltrometer has a porous sintered stainless steel disk which will not allow water to leak in open air The small diameter of the disk allows for undisturbed measurements on relatively level soil surfaces Once you place the infiltrometer on a soil water begins to leave the lower chamber and infiltrate into the soil at a rate determined by the hydraulic properties of the soil As the water level drops you record the volume at specific time intervals like every 30 seconds for a silt loam soil You can then plot this data using the Microsoft Excel spread sheet www decagon com macro to calculate the hydrau lic conductivity see page 14 for more information about using the spreadsheet macto Mini Disk Infiltrometer 2 The Infiltrometer Features stopper suction control tube bubble chamber chamber barrier Mariotte tube water reservoir Sintered steel disc Fig 1 Infiltrometer diagram Mini Disk Infiltrometer 2 The Infiltrometer H
9. lating the van Genuchten parameters for a given soil type to the suction rate and radius of the infiltrometer disk A is computed from 11 65 n l exp 2 92 n 1 9 oh n gt 1 9 A ar 3 pm 11 65 n Dexp 7 5 n 1 9 an ar n lt 1 9 15 Mini Disk Infiltrometer 4 Collecting Data where 7 and are the van Genuchten parameters for the soil r is the disk radius and 4 is the suction at the disk surface The Mini Disk Infiltrometer infiltrates water at a suction of 0 5 to 6 cm and has a radius of 2 25 cm The van Genuchten parameters for the 12 texture classes were obtained from Carsel and Parrish 1988 Values of A computed for the Mini Disk Infiltrometer ate given in Table 2 Table 2 van Genuchten parameters for 12 soil tex ture classes and A values for a 2 25 cm disk radius and suction values from 0 5 to 6 cm ho 0 5 1 2 3 4 5 6 Texture n A sand 0 145 2 68 2 84 2 40 1 73 1 24 0 89 0 64 0 46 loamy sand 0 124 2 28 2 99 2 79 2 43 2 12 1 84 1 61 1 40 sandy loam 0 075 1 89 3 88 3 89 3 91 3 93 3 95 3 98 4 00 loam 0 036 1 56 5 46 5 72 6 27 6 87 7 53 8 25 9 05 silt 0 016 1 37 7 92 8 18 8 71 9 29 9 90 10 55 11 24 silt loam 0 020 1 41 7 10 7 37 7 93 8 53 9 19 9 89 10 64 sandy clay 0 059 1 48 3 21 3 52 424 5 11 6 15 7 41 8 92 loam clay loam 0 019 1 31 5 86 6 11 6 64 7 23 7 86 8 55 9 30 silty clay 0
10. mmodate measuring infiltration for the type of soil you are measuring For most soils a suction rate of 2cm should be adequate In particularly sandy soils where infiltration will occur very quickly an adjustment to 6cm may be helpful and for more compact soil where infiltration is much slower a suction rate of 0 5 is recom mended Howevet we generally recommend that adjust ing the suction to rates other than 2cm should be reserved to more advanced usets who ate comfortable with the instrument and theory of operation 11 Mini Disk Infiltrometer 3 Preparation To adjust the suction rate move the suction tube up or down so the water level is even with the desired suction rate marked on the side of the tube If the suction tube is difficult to move apply a small amount of vacuum grease on the tube to ease movement Placement The infiltrometer should be applied to a smooth spot on the soil surface If the surface is not smooth a thin layer of fine silica sand or diatomaceous earth can be applied to the area directly underneath the infiltrometer s stainless steel disk This will ensure good contact between the soil and the infiltrometer When possible we also recommend using a ring stand and clamp to hold the infiltrometer in place 12 Mini Disk Infiltrometer 4 Collecting Data 4 Collecting Data To make the hydraulic conductivity measurement make sure you have first prepared the instrument as described
11. ometer 4 Collecting Data If you are measuring hydraulic conductivity on a soil with a n 1 35 changes to the Zhang 1997 equation proposed by Dohnal et al 2010 have improved estimates of K as compared to the previous equation 0 6 C arg ys E 4 11 65 n 1 exp 34 65 n 1 19 ah 18 Mini Disk Infiltrometer 5 Water Repellency Index 5 Water Repellency Index Lichner et al 2007 proposed an index of soil water repellency R can be determined from the sorptivities of 95 ethanol and water The Mini Disk Infiltrometer can be used for these measurements To do this make sure you have first prepared the instrument as described in Chapter 3 Please note that the water reservoir has to be filled with ethanol to make the ethanol sorptivity measure ments and with fresh or tap water to make the water sorp tivity measurements The bubble chamber is filled with fresh or tap water in both cases and the suction rate of 2cm 1s selected Chapter 3 Then do the following 1 Recotd the starting ethanol volume 2 At time zero place the infiltrometer on the surface ensuring that it makes solid contact with the soil surface 3 Record volume at regular time intervals as the ethanol infiltrates The time interval necessary for different soil types is presented in Chapter 4 Use the Microsoft Excel spreadsheet www decagon com macro to calcu late the cumulative infiltration I cm and square root of time
12. on from any cause are not to be considered a defect but Seller s liability for defective parts shall in no event exceed the furnishing of replacement parts EO B the factory where originally man ufactured Material and equipment covered hereby which is not manufactured by Seller shall be covered only by the warranty of its manufacturer Seller shall not be liable to Buyer for loss damage ot injuries to persons including death or to property or things of whatsoever kind including but not without limitation loss of anticipated profits occasioned by or arising out of the installation Mini Disk Infiltrometer 1 Introduction operation use misuse non use repair or replacement of said material and equipment or out of the use of any method or process for which the same may be employed The use of this equipment constitutes Buyer s acceptance of the terms set forth in this warranty There are no under standings representations or warranties of any kind express implied statutory or otherwise including but without limitation the implied warranties of merchantabi lity and fitness for a particular purpose not expressly set forth herein Mini Disk Infiltrometer 2 The Infiltrometer 2 The Infiltrometer The Mini Disk Infiltrometer is ideal for field measure ments due to its compact size the water needed to oper ate it can easily be carried in a personal water bottle It is also practical for lab and c
13. on with a small negative pressure or suction When the water is under tension or suction it will not enter macropores such as cracks or wormholes but will only move into and through the soil as determined by the hydraulic forces in the soil Mini Disk Infiltrometer 2 The Infiltrometer Saturated conductivity is obtained when all the pores including the large ones such as cracks or wormholes are filled Macropore flow however is extremely variable from place to place and therefore difficult to quantify Infiltrating water under a tension prevents the filling of the macropores and gives a hydraulic conductivity charac teristic of the soil matrix and is less spatially variable Soil hydraulic conductivity is a function of water potential and water content of the soil The decrease in conductivity as the soil dries is due primarily to the movement of air into the soil to replace the water As the air moves in the pathways for water flow between soil particles becomes smaller and more tortuous and flow becomes more difficult Mini Disk Infiltrometer 3 Preparation 3 Preparation To prepare the infiltrometer for measurement do the fol lowing 1 Fill the bubble chamber three quarters full by running water down the suction control tube or removing the upper stopper as shown NOTE Do not use distilled water Soil water bas solutes and clays bave salts on the exchange sites Using distilled water changes the
14. s based on the data gathered in the above steps Use the Excel spreadsheet to estimate the slope S of the cumulative infiltration vs square root of time rela tionship I St where S cm sg is the sorptivity of ethanol 19 Mini Disk Infiltrometer 5 Water Repellency Index 4 Repeat steps 1 3 for water instead of ethanol making where S cms 5 sure to place the infiltrometer far enough away from the wetted zone of the previous measurement The time intervals used for the water infiltration should be the same as for the ethanol infiltration Again use the linear approximation to estimate the slope S of the cumulative infiltration vs the square root of the time relationship Les fe 1 3 is the sorptivity of water The repellency index R is computed from R 1 95 S S It should be mentioned that ethanol can dam age the numbering on the water ethanol reservoir so care must be taken to avoid spillage NOTE Only the infiltrometers with poly carbonate water reservoirs produced after 2005 should be filled with ethanol 20 Mini Disk Infiltrometer 6 Maintenance 6 Maintenance Cleaning All of the infiltrometer parts can be cleaned using mild soap and water The stainless steel disk can be cleaned with a brush ot even run in a dishwasher Since it is stain less steel it will not rust cleans easily and won t snag or tear on rags when washing Suction Tube If the suction r
15. the data gathered in the above steps The spreadsheet may be downloaded at http www decagon com macro To use this spreadsheet first make sure that your PC has Micro soft Excel installed Then do the following 1 Open the file You will see a table similar to the one above 2 Input the volume levels you recorded into the corre sponding volume column and correlated with the time column on the left You may need to extend the columns depending on how much data you have 14 Mini Disk Infiltrometer 4 Collecting Data recorded The square root of time column and infiltra tion column will change automatically based on your data and the graph on the right of the table will update to reflect the changes 3 Save the data as a new spreadsheet on your hard drive Calculate Infiltration A number of methods are available for determining soil hydraulic conductivity from these data The method pro posed by Zhang 1997 is quite simple and works well for measurements of infiltration into dry soil The method requires measuring cumulative infiltration vs time and fit ting the results with the function ISCHCa 1 a where C m s and C m sj 2 are parameters C is related to hydraulic conductivity and C is the soil sorptivity The hydraulic conductivity of the soil is then computed from k Q where C is the slope of the curve of the cumulative infiltra tion vs the square root of time and is a value re
16. ydraulic Conductivity The knowledge of hydraulic conductivity benefits scien tists land managers and growers by indicating how quickly water will infiltrate when applied to a given field or soll type Infiltration 1s also relevant in contaminant trans port ground water recharge and ecosystem sustainability The hydraulic conductivity of the soil is the rate at which water can move through the soil under certain conditions and hydraulic gradients Water movement through soil typically happens under saturated and unsaturated condi tions Because the Mini Disk Infiltrometer is a tension infiltrometer it measures the unsaturated hydraulic con ductivity of the medium it is placed on at different applied tensions Flow through an unsaturated soil is more com plicated than flow through continuously saturated pore spaces Macropores are filled with air leaving only finer pores to accommodate water movement Therefore the hydraulic conductivity of the soil is strongly dependent on the detailed pore geometry water content and differences in matric potential Rose 1966 Brady and Weil 1999 The Mini Disk Infiltrometer measures the hydraulic con ductivity of the medium it is placed upon Because the infiltrometer has an adjustable suction 0 5 to 7 cm you can get additional information about the soil by eliminat ing macropores with an air entry value smaller than the suction of the infiltrometer This is done by controlling the infiltrati
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