Lecture 19Landfill hydrologyLandfill hydrologyWater balance during active fillingWater balance after closureME term - Moisture extractionSoil moistureSoil moisture vs. timeSoil moisture replenishmentSoil moisture replenishmentTypical soil propertiesTypical soil propertiesSoil moisture vs. timeAnnual water-table cycleAnnual water-table cycleWater-balance methodsThornthwaite water balanceThornthwaite water balanceThornthwaite balance for MassachusettsThornthwaite balance for MassachusettsHumid climatesSubhumid and humid climatesDry climatesThornthwaite and Mather, 1957Steps 1 and 2 in Thornthwaite balanceSteps 3 and 4 in Thornthwaite balanceSteps 5 and 6 in Thornthwaite balanceStep 7 in Thornthwaite balanceRunoff coefficients for landfillSteps 8 and 9 in Thornthwaite balanceStep 10 in Thornthwaite balanceMoisture capacityStep 11 in Thornthwaite balanceSteps 12 and 13 in Thornthwaite balanceStep 14 in Thornthwaite balance !!!What does Thornthwaite balance give us?HELPHELP model capabilitiesHELP model capabilitiesHELP componentsHELP componentsHELP ComponentsHELP componentsLimitations of modelLimitations with HELP modelLecture 19Landfill hydrologyLandfill hydrologyTranspirationInterception EvaporationInterceptionSnowEvaporationSnow AccumulationSnow MeltRunoffRainfall/SnowfallPlant GrowthInfiltrationLateral Drainage Depth of HeadBarrier Soil PercolationWater PathwaysAdapted from: Peyton, R. L. and P. R. Schroeder. "Water Balance for Landfills." Geotechnical Practice for WasteDisposal. Edited by D. E. Daniel. New York: Chapman & Hall, 1993.Vertical PercolationSoil EvaporationWater balance during active fillingL = P + S – E –WAL = leachateP = precipitationS = liquid squeezed from solid wasteE = evaporationWA = water adsorbed into solid wasteWater balance after closureL = P + SM – RO – ET – DS – Q – WA + ME P = precipitationSM = snowmelt infiltrationRO = runoffET = evapotranspirationDS = soil moisture storageQ = lateral drainage in cap drainage layerWA = water adsorbed into solid wasteME = moisture extraction from wasteME term - Moisture extractionMoisture extraction occurs via landfill gas collection systemEnhanced by heat in landfill 27 to 52ºC; 80 to 125ºFEvery million m3of gas extracted includes 6.7 to 81 m3of condensateSoil moistureSoil moisture varies between:Saturation – 100% of pore space filled by waterIf allowed to drain by gravity → field capacityTypically reached in about 2 daysEvapotranspiration can remove additional water → wilting pointDuplicated in lab with suction of 25 atmospheresDifference between field capacity and wilting point is available waterSoil moisture vs. time~2 dayssaturationfield capacitywilting pointsoil moisturecontentavailablewaterWith ETWithout ETtimeSoil moisture replenishmentSoil still drybelowwetting frontSoil nowwetted tofield capacityRainfallWettingfrontDry soil –Initially atwilting pointSoil moisture replenishmentDepth of soil determines how much rainfall is needed to bring soil to field capacity throughout soil columnIn dry climates, there is never enough rainfall to wet entire soil column and there is never ground-water rechargeTypical soil propertiesSoil Saturation(porosity)Field capacityWilting pointSand 0.39 0.09 0.05Sandy loam 0.40 0.18 0.06Loam 0.43 0.24 0.12Clay 0.42 0.40 0.20MSW 0.67 0.29 0.08All properties are expressed as fractions of bulk volume.Typical soil propertiesLoam is a term from soil science to describe soils that contain a mix of clay, silt, and sand Centimeters Per 100 cm Soil DepthPercent, Soil VolumeSandFinesandSandy loamLoamWilting PointAvailable WaterField CapacityClay loam Clay 0 816Siltloam24 320 81624 32Adapted from: Foth, H. D. Fundamentals of Soil Science. 8th ed. New York: John Wiley & Sons, 1990.Soil moisture vs. timeSoil moisture content constantly fluctuates:Increased by rainfallDecreased by ETSoil moisture has great influence on ground-water rechargeAnnual water-table cycle0.00.51.01.52.02.53.03.54.04.55.0Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMonthPrecipitation (inches)16.51717.51818.51919.52020.5Depth to ground water (feet)Precipitation (inches)Depth to water table (ft)Annual water-table cycle0.00.51.01.52.02.53.03.54.04.55.0Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMonthPrecipitation (inches)16.51717.51818.51919.52020.5Depth to ground water (feet)Precipitation (inches)Evapotranspiration (inches)Depth to water table (ft)Water-balance methodsThornthwaite water balance – completed manually (also called the Water Balance Method)HELP model – computer programThornthwaite water balanceTabular procedure to determine water balanceOriginally developed for natural soils, subsequently adapted to landfill analysisPerforms month-to-month bookkeeping of precipitation, ET, and soil moistureThornthwaite water balanceC.W. Thornthwaite, 1948. An approach toward a rational classification of climate. Geographical Review, Vol. 38, No. 1, Pp. 55-94. C.W. Thornthwaite and J.R. Mather, 1955. The water balance. Publications in Climatology, Vol. 8, No. 1, pp. 5-86. Laboratory of Climatology, Drexel Institute of Technology, Centerton, New Jersey.C.W. Thornthwaite and J.R. Mather, 1957. Instructions and tables for computing potential evapotranspiration and the water balance. Publications in Climatology, Vol. 10, No. 3, pp.185-311. Laboratory of Climatology, Drexel Institute of Technology,Centerton, New Jersey. (downloadable from course web site)McBean, E.A., F.A. Rovers and G.J. Farquhar, 1995. Solid Waste Landfill Engineering and Design. Prentice Hall PTR, Englewood Cliffs, New Jersey.Thornthwaite balance for MassachusettsJan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec YearT, Air temperature (F) 24.3 25.9 34.4 46.3 57 66.9 72.1 70 62.4 51.9 40.6 28.7T, Air temperature (C) -4.3 -3.4 1.3 7.9 13.9 19.4 22.3 21.1 16.9 11.1 4.8 -1.8i, Heat index 0 0 0.13 2.02 4.69 7.78 9.6 8.85 6.31 3.33 0.93 0 43.64UPET, Unadjusted PE (inches) 0 0 0 0.03 0.07 0.11 0.14 0.13 0.09 0.05 0.02 0r, PE Adjustment factor 24.5 24.6 30.8 33.6 37.8 38.2 38.5 35.4 31.2 28.5 24.6 23.4PET, Potential Evapotranspiration (inches) 0 0.0 0.0 1.0 2.6 4.2 5.4 4.6 2.8 1.4 0.5 0.0 22.6P, Precipitation (inches) 3.5 3.6 4.3 4.0 3.7 3.5 3.4 3.3 3.5 3.6 4.7 4.5 45.7Cro, Runoff coefficient 0.20.20.20.20.20.20.20.20.20.20.20.2RO, Runoff (inches) 0.70.70.90.80.70.70.70.70.70.70.90.99.1I, infiltration 2.82.93.43.22.92.82.82.62.82.93.83.636.6I-PET (inches) 2.8 2.9 3.4 2.2 0.3 -1.4 -2.6 -2.0 0.0 1.5 3.3 3.6 14.0ACC WL, Accumulated