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1. y 22 Drain Gauge G3 User s Manual 4 Using the Drain Gauge G3 Overview The Drain Gauge G3 measures the total drainage by accumulat ing a representative drainage sample in the reservoir section If the volume of water accumulated in the reservoir section is divided by the cross sectional surface area of the intake of the DCT the total drainage can be calculated with units of m drain age m soil surface are or more commonly simply cm of drain age The water in the reservoir section is easily accessed by the sample tube and can be removed using the pump included with the Drain Gauge G3 for chemical analysis in the laboratory If the concentration of the constituent of interest is measured it can be multiplied by the drainage flux density to yield the flux density of the constituent through the soil Collecting Water Supplied with the Drain Gauge G3 is a peristaltic pump and a 1 L sampling bottle The cap for the sampling bottle has two connec tors for hoses Connect the sample evacuation tube coming out of the drain gauge to one of the ports Then connect supplied second hose from the other port in the sampling bottle to the inlet port of the peristaltic pump Begin rotating the handle on the pump counterclockwise continuously This will create a vac uum inside of the sampling bottle pulling the collected drainage water out of the Drain Gauge G3 s sampling reservoir and into th
2. Drain Gauge G3 User s Manual 1 Introduction 1 Introduction eee Thank you for purchasing the Drain Gauge G3 The Drain Gauge G3 is designed for long term monitoring of soil water drainage with an estimated minimum 10 year lifetime The Drain Gauge G3 also has a collection system that allows for rapid sam pling of drainage waters This innovative device will enable you to monitor soil water movement and chemical leaching accurately and affordably Customer Service and Tech Support When contacting us via fax or email include the following information Your G3 s serial number your name address phone and fax number and a description of your problem Phone Call Monday Friday between 8 a m and 5 p m PST US and Canada toll free 1 800 755 2751 Outside of the US and Canada 509 332 2756 Fax 509 332 5158 E mail support decagon com NOTE If you purchased your G3 through a distributor please contact them for assistance Drain Gauge G3 User s Manual l Introduction Warranty The Drain Gauge G3 has a one year warranty on parts and labor It is activated upon the arrival of the instrument at your location 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
3. Location Selection The location that is chosen for Drain Gauge G3 installation must match the objectives of the particular drainage study For many studies an estimate of the average groundwater recharge from the study site is desired In this case it is important to choose installation location s that are representative of the study site as a whole and several characteristics of the study site must be accounted for 1 Vegetation Once water has percolated more than a few centimeters into the soil the main mechanism by which water is transported from the soil to the atmosphere is through veg etative transpiration It is desirable that the Drain Gauge G3 be installed at a location with vegetative cover that it repre sentative of the whole area of interest It is also particularly critical that vegetation be re established above the Drain Gauge G3 after installation 2 Topography It is best to avoid low areas where runoff col lection can cause uncharacteristically high drainage rates Typically most accurate drainage results are measured at loca tions with a level surface although installations on slopes can yield good results if the installation location is properly restored to natural conditions 3 Location Disturbance For most accurate drainage mea surement it is critical to re establish natural conditions above the Drain Gauge G3 after installation and is therefore best to 12 Drain Gauge G3 User s Manual 3
4. Installing the G3 disturb the location as little as possible during installation With the Drain Gauge G3 significant location disturbance is inevitable but there are strategies to minimize location distur bance We suggest that you select one location for your installation but select a second location nearby that you will use to collect an intact soil monolith in the DCT The mono lith location should be close enough to the installation loca tion that soil properties are similar between the two locations but far enough away that excavation activities at the monolith location don t impact the installation location This method allows you to use whatever methods are most convenient to fill the DCT with an intact monolith i e heavy equipment while still minimizing disturbance at your installation site Typically the site where the monolith is collected and the installation site are on the order of 10 m apart Installation Depth The depth of the Drain Gauge G3 installation depends on the depth of the root zone The objective of the installation is to place the union between the DCT and the wick section below the root zone of the cover vegetation If the union between the DCT and the wick section is placed in the root zone then the Drain Gauge G3 can intercept water that normally would be transpired from the soil by the vegetative cover thus overestimat ing the amount of drainage It is acceptable and expected that the upper sect
5. yielding the total accumulated drainage in units of cm Priming the Drain Gauge G3 The end of the Drain Gauge G3 sample tube is situated slightly above the floor of the access tube This is also slightly above the level of the floor of the reservoir section This creates a dead volume of 47 mL of accumulated drainage water that cannot be removed using the sample tube When the Drain Gauge G3 is first installed into the soil this volume does not contain water so 24 Drain Gauge G3 User s Manual 4 Using the Drain Gauge G3 a total of 47 mL of drainage water will need to be accumulated before the Drain Gauge G3 will begin to record drainage We recommend that you prime the Drain Gauge G3 after installation by adding 250 mL or more of water through the access tube Then you should remove all possible water by evacuating from the sample tube with the included pump This will effectively fill the dead volume and ensure that any subsequent drainage is recorded accurately Calculating Concentration Collected drainage water can be easily and quickly removed from the Drain Gauge G3 through the sample tube using the included pump and sampling bottle The concentration of the constitu ent s of interest can then be determined through laboratory analysis The end of the Drain Gauge G3 sample tube is situated slightly above the floor of the access tube If all possible water is removed to the level of the end of the sample tube 47
6. Drain Gauge G3 rather than into it The divergence control tube DCT on the top of the Drain Gauge G3 is also for the purpose of maintaining vertical flow above the Gauge so that the Drain Gauge G3 intercepts a representative sample Both the amount of sample and its chemical composition need to be representative of deep drainage in the area where the Drain Gauge G3 is installed Whether or not this is true is determined largely by the installation The main issues ate e Depth of installation and root incursion e Soil water divergence convergence e Soil disturbance above the Drain Gauge G3 e Contact between the wick and the soil profile Following are some general comments related to these issues Specific installation procedures are then outlined in the next chapter Depth of Installation Root Incursion In any soil profile there is a zone of recharge and seasonal deple tion extending to the bottom of the root zone The Drain Gauge Drain Gauge G3 User s Manual 2 How the G3 Works G3 should be placed with the union between the DCT and the wick section below the root zone of the cover vegetation If the union between the DCT and the wick section is placed in the root zone the Drain Gauge G3 can intercept water that normally would be transpired from the soil by the vegetative cover thus overestimating the amount of drainage There have also been cases of roots growing down through the wick and impeding flow through t
7. hn slun i hh nie Figure 3 Initial excavation for Drain Gauge G3 Installation 3 Make a vertical hole at least 16 inches 41 cm in diameter to the level of the junction between the DCT and the reservoir section 25 inches 635 cm below the top of the DCT 4 Method 1 offset holes Starting at the floor of the 16 inch diameter hole make a 10 inch 25 4 cm diameter vertical hole to the depth of the bottom of the reservoir section approximately 33 inches 84 cm below the junction between the bottom of the 16 inch hole to accommodate the reser voit section The center of the 10 inch hole should be offset from the center of the 16 inch hole by 3 inches In other words the outer edge of the 10 inch hole should be flush 17 Drain Gauge G3 User s Manual 3 Installing the G3 with the outer edge of the 16 in hole With the offset hole configuration the shelf formed at the end of the 16 inch hole helps to support the weight of the Drain Gauge G3 during installation and minimizes the amount of backfilling neces sary 5 Method 2 straight hole Continue the 16 inch vertical hole from 3 above to the depth of the bottom of the reservoir section approximately 58 inches 147 cm below the top of the DCT This method is easier to accomplish in practice but requires more significant backfilling of soil around the reservoir section of the Drain Gauge G3 Installing the Apparatus 1 Loop a length of heavy rope or strap b
8. mL of drainage water will remain in the lowest portion of the access tube and in the lowest portion of the reservoir section This drainage water will mix with any new soil solution that is col lected by the Drain Gauge G3 The chemical concentration of a sample that is subsequently removed for analysis will then repre sent a weighted average of the chemical concentration of the remnant drainage water and the newly accumulated drainage water For many applications this is acceptable but for some only the chemical concentration of the newly accumulated drain age water is desired This can be calculated by 25 Drain Gauge G3 User s Manual 4 Using the Drain Gauge G3 Cal new Voia z Coia Voia new V new Where C is constituent concentration V is volume of drainage water and the subscripts new old and mix indicate newly accu mulated drainage water drainage water remaining in the reservoir chamber after the previous extraction and the mixture of the two types of drainage water respectively An example calculation follows The nitrate concentration of drainage water that was removed from a Drain Gauge G3 just prior to fertilization of a corn crop was 30 mg L When the water was extracted a few weeks follow ing application of urea 500 mL of drainage water was extracted with a nitrate concentration of 45 mg L Cmi 45 mg L Vaew 500mL Vold 47 mL Cold 30 mg L 458 0 500L 0 047 L 308 0
9. the DCT Use a flat blade or other utensil to cut the soil at the bottom edge of the DCT resulting in a flat soil face at the lower boundary of the DCT 7 Lift the DCT with intact monolith out of the hole Assembling the Drain Gauge G3 Once the installation depth has been chosen and the intact mono lith has been collected in the DCT if desired you are ready to assemble the Drain Gauge G3 1 Add a layer of diatomaceous earth DE on top of the fiber glass fabric on the top of the wick section or on the bottom of the DCT with the intact monolith The DE ensures good hydraulic contact between the soil in the DCT and the wick 15 Drain Gauge G3 User s Manual 3 Installing the G3 2 and also filters fine particulates from the drainage water keeping the Drain Gauge G3 from accumulating soil or silt ing up over time Attach the DCT to the wick section Loosen the screw on the hose clamp at the top of the rubber union sleeve until the hose clamp is visibly loose a Insert the DCT into the rubber union sleeve until the soil column at the bottom of the DCT seats snugly against the layer of DE If the DCT does not contain an intact soil monolith simply seat the bottom of the DCT against the fiberglass fabric If you are having trouble getting the DCT into the rubber union sleeve you can use a screwdriver or other thin object to work the rubber union sleeve out and around the DCT b Tighten the hose clamp un
10. 047L L L mg Cop e See 0 500L L For this calculation to be valid the reservoir must be fully emp tied to the level of the bottom of the sample tube during the evacuation previous to the analysis and during the evacuation used for the analysis 26 Drain Gauge G3 User s Manual 4 Using the Drain Gauge G3 NOTE Because the Drain Gauge G3 is a completely sealed system and does not have an overflow tube it will need to be emptied periodically to prevent the water level from reaching the bottom of the wick If the water level reaches the wick it will change the tension that the wick is applying as it continues to rise above the bottom of the wick This will not cause damage to the Drain Gauge G3 but it may reduce your collection efficiencies Zi Drain Gauge G3 User s Manual Further Reading Further Reading EE O a ME Gee G W B D Newman S R Green R Meissner H Rupp Z F Zhang J M Keller W J Waugh M van der Velde and J Salazar 2009 Passive wick fluxmeters Design considerations and field applications Water Resour Res 45 W04420 doi 10 1029 2008WR007088 Declaration of Conformity nO EUO Application of Council Directive Standards to which Conformity is Declared Manufacturers Name Type of Equipment Model Number Year of First Manufacture 89 336 EEC EN61326 1998 EN55022 1998 Decagon Devices Inc 2365 NE Hopkins Court Pullman WA 99163 USA Gee Pass
11. Drain Gauge Model G3 Operator s Manual Version 0 DECAGON DEVICES Decagon Devices Inc 2365 NE Hopkins Court Pullman WA 99163 USA support decagon com tel 1 509 332 2756 fax 509 332 5158 www decagon com Drain Gauge G3 User s Manual Table of Contents 1 Introduction os g364 58h 4 54 oes e445 oes 1 Customer Service and Tech Support 1 Warranty 9 onda al Aceh Rod Seda pee ene 2 Seller s Liability etc ke oho wa a we eats peda 8 2 SpPEGIHCAHO NS i a ch E EEA E T a ONS 3 2 How the G3 WOLrksS s 66 6 0 S44 H84OSESS 4 Thebis bial dot ee a A Sia eas 4 Depth of Installation Root Incursion 6 Divergence Convergence of Soil Water 8 Soil Disturbance 0 0 eee 11 Soil Wick Contact 2 o n onenen eee eae 11 3 Installing the GS o5 6 5 52 ose Ge he Soo 3 12 Location Selection 0 0 0 12 Installation Depitts 14 cs aise gma aeaosese as 13 Collecting an Intact Soil Monolith 14 Assembling the Drain Gauge G3 15 Making the Installation Hole 17 Installing the Apparatus os indenting ea es 18 Aboveground Tubing Terminations 20 Water Balances 3s tcisedidi dite 3 atl a N 21 4 Using the Drain Gauge G3 22 Collecting Water n a unusnnnuunnnnrn rea 23 Calculating Drainage suuuusuns serren 24 Priming the Drain Gauge G3 004 24 Calculating Concentration 6 0008 s a es 25 Drain Gauge G3 User s Manual
12. deep the Drain Gauge G3 should be installed Place the DCT on the exposed soil in the hole that you have just excavated Press or pound the DCT into the soil The most convenient method for inserting the DCT into the soil is to use heavy equipment e g backhoe or front end loader to apply the downward force However it is possible to pound the DCT into the soil with a heavy sledgehammer With either method 14 Drain Gauge G3 User s Manual 3 Installing the G3 it is critical to distribute the insertion force to avoid damaging the top edge of the DCT This is commonly accomplished by placing one or more 4 X 4 wood boards on the top edge of the DCT before pushing or pounding it in The amount of force needed to insert the DCT is reduced considerably by removing the soil around the portion of the DCT that has already been inserted In other words push or pound the DCT in for a few inches dig down around the outside of the DCT and remove the soil to the depth of the cutting edge of the DCT then repeat In some situations e g stony soil it may not be possible to push or pound the DCT into the soil to collect an intact monolith In this case a re packed mono lith is the only option See instructions for filling the DCT with soil in the Installing the apparatus section below for more information on this option Once the DCT has been fully inserted into the soil dig a large enough hole around it to access the bottom edge of
13. due to corrosion from any cause ate not to be considered a defect but Seller s liability for defective parts shall in no event exceed the furnishing of replacement parts F O B the factory where origi nally manufactured 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 or 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 operation use misuse nonuse 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 understandings representations or warranties of any kind express implied statu tory or otherwise including but without limitation the implied warranties of merchantability and fitness for a particular pur pose not expressly set forth herein Drain Gauge G3 User s Manual 1 Introduction Specifications Suction at intake 110 cm 11 kPa Solution collection capacity 3 1L 6 1 cm of drainage to bottom of wick Additional 5 1L 10 cm of drainage of reserve capacity in wick chamber Solution collection surface area 507 cm 25 4 cm inside dia
14. e sampling bottle Because the reservoir has a higher capacity than the sampling bottle you may need to stop pumping if the sampling bottle becomes full and empty the solution into a sec ondary bottle Continue this process until water stops flowing into the sampling bottle The reservoir should now be empty 23 Drain Gauge G3 User s Manual 4 Using the Drain Gauge G3 The total volume of sample that was pulled will be used to calcu late drainage and contaminant flux rates In order to prevent cross contamination between samples and across different locations it is important to rinse out the sampling bottle and associated parts before pulling another sample Take apart the cap and bottle assembly and rinse all of the parts that came into contact with the sampled water using distilled water 3 times The pump does not need to be rinsed out since it does not come into contact with any of the sampled water NOTE If the pump becomes hard to turn you may open the pump and apply lubricating grease to the internal apparatus Calculating Drainage The inner diameter of the DCT is 25 4 cm 10 0 inches which yields a cross sectional surface area of 506 7 cm 78 5 in at the intake of the Drain Gauge G3 The amount of drainage can eas ily be calculated by the change in volume of water accumulated in the reservoir section Simply divide the volume of water removed em by the cross sectional surface area of the DCT intake 506 7 cm
15. e will act to retard flow and can cause flux divergence b Horizonation Try to pack the soil back into the DCT in layers that correspond to the horizons in the surrounding soil 3 Carefully backfill soil into the hole around the reservoir sec tion The more soil you are able to backfill into this section 19 Drain Gauge G3 User s Manual 3 Installing the G3 the better as the Drain Gauge G3 is less likely to settle over time if this section is full of soil Backfill soil around the DCT Try to achieve a similar bulk density to the surrounding soil Carefully replace the soil above the DCT and vegetation that were removed as described at the beginning of making the installation hole section Be careful to re pack the soil above the DCT to the same bulk density as the surrounding soil and to re create any layering that is present in the natural soil Also be careful not to leave a mound or depression of soil above the Drain Gauge G3 as this could significantly affect infiltration of water in the area of the Drain Gauge G3 If there is vegetative cover above the Drain Gauge G3 it may be desirable to water in the disturbed vegetation to help it re establish as soon as possible Aboveground Tubing Terminations 1 Now that the Drain Gauge G3 is installed in the ground the sampling tube coming out of the access tube needs to be run through the U connector Then connect the U connec tor to the top of the acces
16. elow the fitting con necting the reservoir section to the access tube immediately below the junction between the DCT and reservoir section See figure 4 below Caution If you are using an intact monolith when turning the Drain Gauge G3 upright it is important to not lift the drain gauge up using the bottom part of the sampling chamber as a lift point Doing this could result in a break around PVC fittings or the seal around the wick section 2 Carefully lower the Drain Gauge G3 into the installation hole with one person holding the Drain Gauge G3 level and guid ing it into the installation hole while another person s slowly lowers it into the hole using the loop of rope or strap this job typically take 2 to 3 people slowly lower the Drain Gauge G3 into the hole Do not drop the Drain Gauge G3 into the hole or it could be permanently damaged 18 Drain Gauge G3 User s Manual 3 Installing the G3 Figure 4 How to safely lower the Drain Gauge into the installation hole 3 Filling the DCT with a disturbed sample ignore this section if you collected an intact monolith in the DCT If you did not collect an intact monolith it is important to re pack the disturbed soil in the DCT as similarly as possible to the natu ral soil conditions a Bulk density When backfilling the DCT it is important to pack the soil back to the natural bulk density Try to avoid large variations in bulk density between layers as thes
17. he wick as well as pulling water from the reservoir thereby reducing the amount of measured drainage substantially A patch of Biobarrier root inhibitor fabric is included with each Drain Gauge G3 This fabric has beads impregnated with trifluralin which prevents root tip cell division and thereby acts as a root elongation inhibitor with 20 years of effective lifetime This fabric has been shown to effectively keep roots from pene trating the Drain Gauge G3 wick section In some situations where trifluralin or trifluralin breakdown products might com promise specialized chemical analysis of drainage water the Biobarrier fabric can be removed from the Drain Gauge G3 assembly Contact Decagon for instructions on removing the Biobarrier fabric without compromising the effectiveness of the capillary wick system In cases where the Biobarrier fabric is removed it is especially critical to get the Drain Gauge G3 buried below the root zone Since root density decreases with depth the bottom of this zone may be difficult to locate In annual crops it is typically around 1 m 3 ft but can be much deeper in perennials There is of course a practical limit to how deep the Drain Gauge G3 can be installed With shallow rooted crops this is not an issue but with deep rooted plants one may need to strike a compromise between getting below all roots and installing the Drain Gauge G3 at a practical depth Even when roots go quite deep the amount of
18. ion of the DCT be placed in the root zone as long as vegetation is re established above the Drain Gauge G3 and normal root growth is present in the DCT Because the installation depth is determined by vegetative rooting depth the depth of installation will vary from location to loca tion In some instances where the root zone is nonexistent or 13 Drain Gauge G3 User s Manual 3 Installing the G3 shallow e g bare soil turfgrass it is possible to install the Drain Gauge G3 with the DCT extending all the way to the surface This type of installation has the advantage of preventing flow divergence or convergence However it can be difficult to re establish natural surface conditions and surface vegetation if the DCT is extended to the surface Collecting an Intact Soil Monolith in the DCT Stainless Steel DCT only 1 If you do not wish to collect an intact soil core monolith in the DCT and would rather use a disturbed soil sample skip this section and go straight to the Assembling the Drain Gauge G3 section below Select the location where you will collect the intact monolith We recommend that you collect your monolith at a separate but nearby location from where you will install the Drain Gauge G3 see the comments in the Location Selection sec tion above Excavate to the level that you have determined to be optimal for the top of the DCT See the Installation depth section above for help determining how
19. ive Capillary Lysimeter Drain Gauge G3 2010 28 Drain Gauge G3 User s Manual Declaration of Conformity This is to certify that the Drain Gauge G3 manufactured by Decagon Devices Inc a corporation based in Pullman Washing ton USA meets or exceeds the standards for CE compliance as per the Council Directives noted above All instruments are built at the factory at Decagon and pertinent testing documentation is freely available for verification 29 Drain Gauge G3 User s Manual Declaration of Conformity 30 Drain Gauge User s Manual Index Index Cc CE compliance 29 Customer Service 1 D Declaration of Conformity 29 Divergence control tube DCT 4 9 Drain gauge assembly 15 depth of installation 6 installation instructions 4 12 priming 24 Drainage calculating 24 E E mail address 1 F Fax number 1 l Installation 4 12 depth 13 location 12 making the hole 17 soil disturbance 11 Intact soil monolith 14 31 Drain Gauge User s Manual Index P Peristaltic pump 23 Root incursion 6 S Seller s liability 2 Soil disturbance 11 Specifications 3 T Telephone 1 U U connector 20 W Warranty 2 Water collection 23 32
20. meter Solution extraction Maximum extraction depth approximately 8m Wetted Materials DCT standard 304 stainless steel 11 gauge DCT optional inert material PVC Wick dry fired fiberglass Root inhibitor Treflan BioBarrier removable Sample evacuation tube Polyethylene Hydraulic bridge material Diatomaceous Earth DE All other parts PVC Dimensions Total length 147 cm DCT length 63 5 cm DCT outside diameter 26 4 cm Reservoir length 81 3 cm Reservoir outside diameter 11 5 cm Access tube length 180 cm standard customizable Access tube outside diameter 6 0 cm 2 schedule 40 PVC Sample evacuation tube 1 27 cm OD X 0 79 cm ID X 5m length standard Mass 20 kg with Stainless Steel DCT 14 kg with PVC DCT Drain Gauge G3 User s Manual 2 How the G3 Works 2 How the G3 Works The Drain Gauge G3 is installed below the root zone Water infil trates down through the soil and enters the divergence control tube DCT It then flows down through a fiberglass wick into a reservoir see Fig 1 The water is stored in a measurement reser voir until a sample can be removed The volume of the removed sample can be used to calculate the total drainage since the last date the reservoir was emptied Chemical analysis can also be performed on the sample If the drainage rate and chemical con centration in the drainage water are both known the flux of chemical through the soil can be calculated The
21. n 11 kPa water will preferentially flow into the Drain Gauge G3 flux convergence The chosen suction value of 11 kPa is an intermediate value between saturation and field capacity which define the range of suctions where a significant amount of water will drain through the soil During very wet periods the Drain Gauge G3 may experience flux convergence and during periods between 11 and 33 kPa of suction it may experience flux divergence but the overall integrated flux mea surement should be close to the actual drainage In addition to the fiberglass wick the Drain Gauge G3 makes use of an innovative divergence control tube DCT that serves to minimize flux divergence and convergence and optimize collec tion efficiency of the Drain Gauge G3 Numerical and labora tory simulations performed by Gee et al 2009 have demonstrated the effectiveness of DCT in preventing flux diver gence and convergence around the collection point Figure 2 Drain Gauge G3 User s Manual 2 How the G3 Works shows the modeled collection efficiency of the passive wick lysimeters such as the Drain Gauge G3 as a function of DCT height for six different flux rates in four different soils note that the Drain Gauge G3 DCT is 60 cm long It is apparent that in coatse textuted or structured soils reasonable collection effi ciency is achieved with the standard 60 cm DCT even at low drainage flux rates It is also apparent that in non structured fine text
22. ns and DCT heights Figures from Gee et al 2009 Soil Disturbance It is impossible to install the Drain Gauge G3 without disturbing the soil The goal is to install it in such a way that the disturbance has minimal impact on the Gauge s ability to measure deep drain age accurately In some cases it may be necessary to install the Drain Gauge G3 beneath an undisturbed core of soil In all cases it will be necessary to allow time for roots to grow back into dis turbed soil If the soil surface is tilled there is no point in trying to keep that part of the soil undisturbed since it is already dis turbed The following chapter on installing the Drain Gauge G3 has some specific tips on how to minimize soil disturbance dur ing installation Soil Wick Contact In order for the bottom of the soil profile to be under the proper suction the suction in the wick must be transferred to the bot tom of the soil column There must therefore be good capillary continuity between the soil column and the wick If the Drain Gauge G3 is installed by backfilling with soil the contact is likely to be good without further effort If an undisturbed core is installed capillary continuity is established by placing a layer of diatomaceous earth over the wick The diatomaceous earth con forms to the irregularities of the soil and wick to provide continu ity 11 Drain Gauge G3 User s Manual 3 Installing the G3 3 Installing the G3
23. ory A soil water balance takes into consideration the inputs losses and storage of water in a soil profile An important component of the water balance is the water that drains from the bottom of the soil profile often referred to as deep drainage or deep perco lation This is water that has gone sufficiently far below the root zone that it cannot be removed from the soil by transpiration or evaporation The other components of the water balance can be measured but the deep drainage typically has been computed as the residual when the other components were measured and accounted for Because of uncertainties in the measurements of the other water balance components deep drainage estimates were subject to large errors Drain Gauge G3 User s Manual 2 How the G3 Works Figure 1 Components of the Drain Gauge G3 Drain Gauge G3 User s Manual 2 How the G3 Works The Drain Gauge G3 allows direct measurement of the deep drainage component of the water balance This is accomplished by intercepting and collecting a representative sample of the water that moves below the root zone The Drain Gauge G3 is sometimes referred to as a passive wick lysimeter It has a spe cially treated fiberglass wick which maintains tension on the water at the bottom of the soil profile where it is extracting water Without this tension water would pile up at the outflow boundary and force the water in the soil above to move around the
24. s tube After connecting the U connector to the access tube run the sampling tube through the pre cut slit in the rubber end cap Pull the sampling tube through the end cap until the end cap meets up with the end of the U connector Be sure not to pull the sampling tube too tight because doing so could cause the end of the sampling tube to be pulled up higher in the access tube Connect the end cap with the end of the U connector and tighten the hose clamp with a flat head screw driver 20 Drain Gauge G3 User s Manual 3 Installing the G3 Figure 5 PVC U connector assembly on top of access tube Water Balance It is often useful to install ECH2O soil moisture sensors near the Drain Gauge G3 to observe how the water content changes with depth over time in the soil profile Some users will also install ECH 0 sensors in the DCT to make sure that the soil moisture dynamics in the DCT are similar to those in the undisturbed soil surrounding the Drain Gauge G3 If you install ECH O sensors in the DCT you must take care so they are not touching any part of the DCT as this will adversely affect the readings A good rule is to locate them as close to the center of the DCT as possible Installing a rain gauge near the installation site is also useful for measuring incoming water values for water balance calculations 21 Drain Gauge G3 User s Manual 4 Using the Drain Gauge G3 4 Using the Drain Gauge G3
25. til the rubber union sleeve is sealed to the DCT Extend the access tube to desired length The desired length will be determined by the depth of the Drain Gauge G3 installation Typically the top of the access tube will be 1 3 feet above the ground surface To extend the access tube simply add the two enclosed sections of 2 inch schedule 40 PVC tubing connected by the slip coupling The overall length of the access tube can be customized by cutting the second PVC section to the desired length or by adding addi tional PVC tubing In areas where a high water table is present it is recommended that the PVC connections be glued to prevent water from entering the access tube sam pling chamber 16 Drain Gauge G3 User s Manual 3 Installing the G3 Making the Installation Hole 1 Select a location for your installation allow plenty of room to move around the hole and lay a tarp nearby that can be used to hold the vegetation and soil that will be removed from the site 2 Remove the surface vegetation and place it on the tarp Try to preserve as much of the root mass as possible Also it is important to organize the vegetation you remove so that it can be replaced as closely as possible to its original loca tion Figure 3 pp istelhonclnrtereniliyy O we 4 T A BB d P aa F g 3 P ETE i Sh ae EN a A Lr DEn a i aw AA A y p z A f F p ae Z Wintu Mint Wina 1 ier fee 21 a e 2 4 Wilt ITI iy hinge ee ey Lly he
26. ured soils the standard 60 cm DCT will only result in reason able collection efficiencies at high drainage flux rates However it should be noted that the simulations were conducted with steady state drainage fluxes which would seldom if ever occur in nature Typically drainage is associated with pulsed infiltration events e g rainfall irrigation snow melt where the drainage fluxes are relatively high thus increasing the overall integrated collection efficiency of the Drain Gauge G3 350 350 300 a Sand 1 mma 3 ners Sia 10 mnva 250 100 mnva 250 4 10 mwa 1000 mma ee 20 10000 mma 2 1000 mma s 4 s 10000 mma E 150 iN 1504 5 x 100 Ssa s s 100 4 ta mo gt 50 s4 ae a o T 7 o bee 0 20 6 80 100 0 20 40 GJ 80 100 Control Tube Height cm Control Tube Height om 350 350 so C SiuctuedCiay m 300 d Silt Loam 4 mava 10 mma 10 mwa 250 250 10 ma A ooo mt 200 1000 mva 2004 i zest s 10000 mma s y 150 1504 5 5 x 100 jp 100 4 50 50 4 o S A o cocooo 6 6 a o a 40 60 80 100 o 20 40 60 80 100 Control Tube Height cm Control Tube Height cm 10 Drain Gauge G3 User s Manual 2 How the G3 Works Figure 2 Simulated collection efficiency as a percentage Jm Ja 100X measured actual Jor passive wick lysimeters with 60 cm long wicks in selected soils under a variety of steady state flux conditio
27. water taken up by these roots may be small so install Drain Gauge G3 User s Manual 2 How the G3 Works ing the Drain Gauge G3 within the lower root zone will result in minimal error However if the Drain Gauge G3 is installed in the root zone it is essential that the Biobarrier root inhibitor be included to prevent root incursion into the wick It is standard practice that the upper section of the DCT be placed in the root zone as long as vegetation is re established above the Drain Gauge G3 and normal root growth is present in the DCT In some instances where the root zone is nonexistent or shallow e g bare soil turfgrass it is possible to install the Drain Gauge G3 with the DCT extending all the way to the sur face This type of installation has the advantage of preventing flow divergence or convergence However it can be difficult to re establish natural surface conditions and surface vegetation if the DCT is extended to the surface Divergence Convergence of Soil Water Water in the soil flows in response to differences in soil suction which is the same as water potential but with the opposite sign The two components of soil suction that are important in the water balance are the matric suction which arises from the attrac tion between water and soil particle surfaces and the gravitational suction which arises from gravitational forces pulling on the soil water The important thing to understand is that water al
28. ways flows from low suction high water potential to high suction low water potential Suction in the soil generally ranges from 0 saturation to 100 000 kPa air dry The suction at which there is no longer enough water in the soil to allow significant gravita tional drainage is generally between 10 kPa and 33 kPa and is known as field capacity Drain Gauge G3 User s Manual 2 How the G3 Works For water to enter a lysimeter the suction at the intake must be equal to or greater than the suction in the surrounding soil With traditional pan lysimeters there is a zero suction boundary which means that water will preferentially flow around the lysimeter intake flux divergence unless the soil suction is very close to zero saturation This results in significant underestimation of drainage rates with pan lysimeters The Drain Gauge G3 uses a fiberglass wick to form a hanging water column which pulls con tinuous suction at the intake In a perfect system this suction would vary to match the matric suction of the surrounding soil allowing water to flow into the Drain Gauge G3 in exactly the same manner as it flows through the soil However the wick sys tem is only able to pull a constant suction The suction at the top of the DCT is approximately 11 kPa 50 cm wick plus 60 cm soil column in DCT If the soil is drier than 11 kPa water will pref erentially diverge around the Drain Gauge G3 Conversely if the soil is wetter tha

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