Precipitation-Runoff and Streamflow-Routing Models for the ...

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EvapotranspirationINPUTSAirtemperature Precipitation SolarradiationEvaporationSublimationInterceptionSublimationEvaporationTranspirationTranspirationGround-waterrechargeSoil-zonereservoirRecharge zoneLower zoneSoil-zone excessThroughfallSnowpackSnowmeltImpervious-zonereservoirSubsurfacerechargeEvaporationSubsurfacereservoirSurface runoffSurface runoffSubsurfaceflowGround-waterreservoirGround-water sinkGround-water rechargeGround-water flowStreamflowFigure 2. Flow diagram of the Precipitation-Runoff Modeling System conceptual model.user defined by depth and water-storage characteristics.Transpiration depletes moisture only in the lowerzone, the depth of which is based on the rooting depthof the predominant vegetation type. Surface retentionof water on impervious zones is modeled as a reservoir.A maximum retention-storage capacity for thiszone must be satisfied before surface discharge canoccur. When free of snow, the reservoir is depleted byevaporation.Computation of infiltration is dependent onwhether the input source is rain or snowmelt. For rainfalling on ground with no snow cover, the infiltrationis computed as a function of soil characteristics, antecedentsoil-moisture conditions, and storm size. Surfacerunoff is computed using the contributing- orvariable-source area approach, where a dynamicsource area expands and contracts according to rainfallcharacteristics and the capability (field capacity) of thesoil mantle to store and transmit water (Troendle,1985). As rainfall continues and the ground becomeswetter, the proportion of precipitation diverted to surfacerunoff increases, while the proportion that infiltratesto the soil zone and subsurface reservoirdecreases. Daily infiltration (net precipitation less surfacerunoff) can be computed as either a linear or anonlinear function of antecedent soil moisture andrainfall.For snowmelt, and for rain falling on a snowpack,all water is assumed to infiltrate until field capacity ofthe soil is reached. At field capacity, any additionalsnowmelt is apportioned between infiltration and surfacerunoff. Snowmelt in excess of this capacity contributesto surface runoff. Infiltration in excess of fieldcapacity is first used to satisfy recharge to the groundwaterreservoir. Recharge to the ground-water reservoiris assumed to have a maximum daily limit. Excessinfiltration, after ground-water recharge has been satisfied,will recharge the subsurface reservoir. Wateravailable for infiltration as the result of rain-on-snow istreated as snowmelt if the snowpack is not depleted oras rain if the snowpack is depleted.Input to the subsurface component is water fromthe soil zone in excess of field capacity. Subsurfacemoisture can percolate to the shallow ground-watercomponent or move downslope to some point of dischargeabove the water table. In the model, the rate ofsubsurface flow from this reservoir is computed using8
the storage volume of the reservoir and two userdefinedrouting coefficients.The ground-water reservoir is defined as a linearsystem and is the source of baseflow. Recharge canoriginate from the soil zone (in excess of field capacity)and from the subsurface reservoir. Contributionsfrom the subsurface reservoir are computed daily as afunction of a recharge-rate coefficient and the volumeof water stored in that reservoir. Movement of groundwater out of the system boundaries is accomplished byrouting to a ground-water sink.Many of the equations used in the model requirecoefficients that can be estimated directly from knownor measurable basin characteristics. A few empiricalparameter values, however, can be estimated only bycalibration to observed data. These parameters are primarilyassociated with subsurface and ground-waterreservoirs and snowpack-energy computations.Time-Series DataDaily total precipitation and maximum and minimumair temperature time-series data were used asPRMS model input data for 10 representative basinmodels and for 11 streamflow-routing-network simulations.Daily mean discharge data were used to calibrateand verify model simulations for the representativebasins and was used as both input and verificationfor the streamflow-routing-network simulations.With the exception of three streamflow-routingnetworksimulations (Johnson Creek, McKenzie River,and Willamette River from Salem to Wilsonville), allmodel simulations in the study used data from wateryears 1972 through 1978. For the calibration basins,the first 4 years were used for model calibration, andthe remaining 3 years were used for model verification.PrecipitationPrecipitation data were provided by the Office ofthe State Climatologist, located at Oregon State Universityin Corvallis, Oregon. The data are from a statewideclimate data inventory compiled by the StateClimatologist (Redmond, 1985). Most of the precipitationdata were collected under the auspices of theNational Weather Service Cooperative Program. StandardizedNWS collection equipment was provided tothe program participants. The location names, identificationnumber, latitude and longitude, and elevationsof the climate-data stations used in this study areshown in table 1; site locations are shown in figure 3.Nine of these 54 precipitation-data records containedmissing values, which were estimated by using linearregression equations that incorporated records ofneighboring stations.Air TemperatureDaily maximum and minimum air temperaturedata were also provided by the State Climatologist andcollected by the NWS. Most of the climate stationslisted in table 1 had daily maximum and minimum airtemperature records for the model simulation timeperiods. Twenty of both maximum and minimum airtemperature data records out of 54 total records containedsome missing values. As with precipitationdata, the missing values were estimated using linearregression relations as correlated to records of neighboringstations.DischargeDaily mean discharge values for the 30 gagingstations listed in table 2 were used for both runoff androuting models. Station locations are shown in figure3. All gaging stations were operated by the USGS forthe data time periods used in the model simulations.The data were collected according to standard techniquesof the USGS (Rantz, 1982). Complete recordsof daily streamflow are available in USGS annualwater-data publications. The flow data used in theprecipitation-runoff-model calibration reflect little orno flow regulation.Delineation of Basin PhysicalCharacteristicsPRMS allows the user to define hydrologicresponse variations over the basin surface (Leavesleyand others, 1983). The entire Willamette River Basinwas partitioned into “homogeneous” HRU’s usingcharacteristics such as soil type, land use (vegetationtype), slope, aspect, and geology. The five data layersof different land-surface data and precipitation distributionwere assembled using ARC-INFO, a geographicinformation system (GIS) software package.The HRU’s were defined after merging these data layersinto a composite data layer.Data layers used for creating the HRU’s includedaverage annual precipitation, basin and subbasin delineations,land use, slope, aspect, surficial geology, andsoils. The data layer categories used in the study and9
Page 1: Precipitation-Runoff and Streamflow
Page 4 and 5: U.S. DEPARTMENT OF THE INTERIORBRUC
Page 6 and 7: Determining Travel Time and Dilutio
Page 8 and 9: 2. Stream-gaging stations used to c
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Page 12 and 13: network-routing models where availa
Page 14 and 15: made on the main stem at base-flow
Page 16 and 17: Figure 1. Willamette River Basin, O
Page 20 and 21: Table 1. Climate stations used to c
Page 22 and 23: Table 2. Stream-gaging stations use
Page 24 and 25: Figure 4. Mean annual precipitation
Page 26 and 27: Major Land Use MapHydrologic Soil G
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Page 34 and 35: Table 8. Selected monthly basinwide
Page 36 and 37: Figure 9. Location of Precipitation
Page 38 and 39: Table 11. Statistical analyses of P
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Page 46 and 47: 3,0002,500June 21-30, 1993September
Page 48 and 49: stream network is shown on figure 1
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Page 52 and 53: 123˚22´30´´ 123˚15´ 123˚00´
Page 54 and 55: 123˚00´´ 45´30´122˚15´45˚15
Page 56 and 57: YamhillRiver123˚45´ 30´ 15´123
Page 58 and 59: 123˚07´30´´ 123˚00´ 45´ 30´
Page 60 and 61: 123˚07´30´´ 123˚00´ 45´ 30´
Page 62 and 63: 44˚15´14166000122˚07´30´´Will
Page 64 and 65: 122˚15´ 122˚00´121˚52´30´´4
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observed flow at the Willamette Riv
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DAFLOW model, and peak amplitude is
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20DYE CONCENTRATION, IN MICROGRAMS
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ARC-INFO and Geographic Information
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WILL.WDMData-base file(Observed pre
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WILL.WDMData-base fileSWSTATSFreque
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Jobson, H.E., 1980, Comment on A ne
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APPENDIX 1. STREAM GEOMETRY FOR MAI
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APPENDIX 2. ARC MACRO LANGUAGE (AML
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APPENDIX 3. DEFINITIONS OF PARAMETE
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APPENDIX 3. DEFINITIONS OF PARAMETE
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APPENDIX 4. MEASUREMENTS USED TO DE
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APPENDIX 5. EXAMPLE PRECIPITATION-R
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APPENDIX 5. EXAMPLE PRECIPITATION-R
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APPENDIX 6. DIFFUSION ANALOGY FLOW
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APPENDIX 7. PROGRAMMING STEPS TO IN
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APPENDIX 8. PROGRAMMING STEPS TO DE
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150Climatemaxtempmintempprecipitati
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APPENDIX 10. DIRECTORY TREE AND DES
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APPENDIX 11. DIRECTORY TREES AND DE
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APPENDIX 11. DIRECTORY TREES AND DE
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APPENDIX 12. DIRECTORY FOR will.wdm
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APPENDIX 13. PROGRAMMING STEPS FOR
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APPENDIX 14. INPUT FILES FOR BRANCH
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