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The contribution &om surface water supplies to meeting the NCIWR was based on the monthly yield of those surface water rights, reduced by the appropriate ditch loss and irrigation application efficiency. Monthly yield data for all subject water rights listed under t�e WAS plan of operation include data. for the 1974 - 2002 period. 2003 monthly diversions for each ditch system were �timated from either (1) provisiona12003 diversion data as reported by the Water Comm�ssioner, or (2) 2002 actual diversion data from HydroBase. Reservoir releases for 1974- 2003 were obtained from the reservoir campany or estimated from end-of-month storage contents as recorded by the Division Engine,er. 2004 monthly diversions and reservoir releases were estimated as the average monthly diversian/release amount for 19742003. Monthly yields for all surface water rights for each farm model unit included monthly river diversions adjusted for ditch loss and pro-rated based on the number of shares listed under the fazm model unit. Table 3 pres�ts a list of the surface water sources listed on member contracts. A water budget analysis was performed on a monthly basis for each fazrn model unit. The water budget compares surface water available to meet the NCIWR after credit from soil moisture and effective precipitation. It was assumed that the alluvial ground water for each farm model unit provided the supply required to meet the unmet NCIWR that was not met by the surface water supplies. The alluvial ground water that satisfied the unmet crop irrigation water requirement, after credit for surface water supplies, was distributed equally to a11 wells under each farm model unit. Depletions for non-irrigation contracts were estimated values based on the type of use. Onsite alluvial ground water depletions for each non-irrigation contract were bas� on estimates of ground water depletions which were developed when each specific contract entity join� the WAS. 3.2 Delayed Stream Depletiona 3.Z.1 General. Delays in depletions from the WAS member wells reaching the South Platte River were estimated using the Streazn Depletion Factor (SDF) method for four of the six Central administrative reaches (see Figure 1). All stream depletions for Reaches A, B, C and F were calculated using the SDF View model developed by IDS at Colorado Staxe University. The SDF method is based on the etnpirical relationship developed by Jenkins: SDF = a� * S/T where SDF = timing of �round watter reharn flow in days, a= distance of the centroid of a parceUwell to the river (ft), S= aquifer storage coefficient (dimensionless), and T = transmissiviiy (ft�/day By mapping the location of each well in a Geographical Information System (GIS), each member well was assigned an SDF value using the SDF bands contained in the SPMAP model developed by IDS at Colorado State University. All member well depletions were estima.ted from p:\��\GEN\CCWCD\25087\SWSP WAS\1A04 WAS SWSP (FINAL).doc ()