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<br />V. Description of Data and Software: South Platte Consumptive Use Model (SPCU) <br /> <br />2.5.1 Imoorting Inout Files from SPGIS <br /> <br />SPGIS can be used to create input files for the <br />SPCU Model. This is done by selecting areas for <br />farms and fields, and assigning crop types and <br />wells to each selected area. SDF values for each <br />well have been assigned based on maps <br />generated from SDF contour maps and the <br />location of the wells. The information generated <br />from SPGIS can then be imported into the CU <br />Model. <br /> <br />2.5.2 Soecifving the Modeling Area <br /> <br />The modeling area can be made up of multiple <br />farms with water supply information specified. <br />Each farm can contain multiple fields that have <br />crop use specified. The model is scaleable, <br />allowing the user to compute consumptive use <br />for an entire river basin or for an individual field. <br />Scenarios can be run to reflect expected land-use <br />or water supply changes. The model has been <br />used to determine consumptive use for potential <br />climate changes on water resources in the Great <br />Plains (Ojima et aI., 1999) and projects to <br />determine water use in one or two fields for one <br />season. <br /> <br />2.5.3 Editing Weather Data <br /> <br />Weather data can be specified by selecting <br />weather stations in the SPGIS interface or can be <br />downloaded from the State's HYDROBASE. <br />Data includes daily maximum and minimum <br />temperatures, precipitation, and frost dates. With <br />the link to the database, weather data can be <br />updated with the latest information for a SPCU <br />Model run. If more data is available for a local <br />area or there is a need to do future projects, data <br />can be entered manually or from spreadsheets. <br /> <br />2.5.4 Water Suoolv Ootions <br /> <br />There are three options that can be set to <br />regulate the use of water for a CU model run. <br /> <br />· The CU of Alfalfa and Grass can be limited <br />by a specified fraction. <br /> <br />· The amount of water specified for winter <br />carry-over can be set to contribute to the <br />consumptive use of crops during the growing <br /> <br />season in the spring and therefore will offset <br />some of the requirements of surface or <br />groundwater supplies. <br /> <br />· If water supply data is specified, surface and <br />groundwater will be used to determine how <br />much water is available for comparison with <br />potential ET to determine shortages and <br />excesses. Water supply information can be <br />specified by importing surface water <br />diversion data from the State's <br />HYDROBASE or ground and surface water <br />supply data can be entered directly by the <br />user. <br /> <br />The water distribution mode includes options <br />to enter individual farm headgate flow or pro- <br />rating a total ditch flow to a farm by applying a <br />conveyance efficiency. Water supply options <br />can be specialized for individual farms or fields. <br />Efficiencies for conveyance of water to the farm <br />can be specified and application efficiencies for <br />fields can be specified. These options allow a <br />sprinkler efficiency to be assigned for sprinkler <br />irrigation systems. <br /> <br />2.5.5 Groundwater Supply and Well <br />Information <br /> <br />There is extensive support for groundwater <br />supply information, including tools for entering <br />pumping records for individual groundwater <br />wells (Figure 7). <br /> <br />Wells in the South Platte basin have a decreed <br />SDF value that has been estimated based on the <br />location of the well. SDF values have also been <br />computed based on GPS locations. This <br />information can be forwarded to SDF View to <br />estimate the depletion impacts to the South <br />Platte River of the well pumping. There are two <br />calculation modes for groundwater in the SPCU <br />Model. Not allowing shortages will assign <br />consumptive use not met by rainfall and surface <br />water sources to be met by wells. Allowing <br />shortages will only use the well discharge <br />measurement supplies and the well application <br />efficiencies specified; unmet consumptive use is <br />listed as a shortage. <br /> <br />Completion Report: South Platte Mapping and Analysis Program <br /> <br />19 <br />