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. A spreadsheet, provided by Helton and Williamsen.. P.C., included monthly well pumping for individual Arkansas River Basin HI Model wells during the years 1986 through 1994. Thesle data were developed as a part of the engineering study for the water court case Kansas vs. Colorado. This investigation found that the 1986 data appeared to be incomplete and some data could have been missing. Therefore, only the 1987 through 1994 data were used in this study. The State of Colorado Division of Water Resources (DWR) has developed historical pumping data for the period 1950 through 1994 for all Arkansas River Basin HI Model wells. The data provided annual pumping totals summed by user group. These data were used to develop the trend in yearly well pumping and were used as base data when calculating estimates for the period 1999 through 2023 (see Appendix III.A-A). Procedure for Estimatinq PumpinQ In order to determine an estimate of future stream depletions due to pumping of CWPDA member wells, it was necessary to develop estimates of future pumping. In this study, historical pumping data provided by the DWR for the years 1970 through 1994 were used to estimate the trends in future pumping during the period 1999 through 2023. The procedure used to estimate . pumping is discussed in the following paragraphs. The 1986-1994 Helton and Williamson spreadsheet was imported as a database table and linked to the CWPDA membership database by using the State's well identification number. CWPDA yearly pumping, for the years 1987 through 1994, was determined by summing individual well pumping, by user group, for those Rule 3 1999 member wells with matching State ID numbers (see Table III.A-2). Review of the data found that several CWDPA member wells were unaccounted for or had limited pumping records in the Helton and Williamsen spreadsheet. It was necessary to adjust the spreadsheet pumping volumes to account for missing and limited data. Monthly pumping (June 1996 through March 1999) for all missing wells was summed and grouped by user group (see Table III.A-3). An adjustment factor was calculated by dividing the missing well pumping by the total volume pumped during the same period for all CWPDA member wells (see Table III.A-3). CWPDA member well pumping from the Helton and Williamson spreadsheet was increased by the adjustment factor for each user group. This determined average annual CWPDA member well pumping for the period 1987 through 1994 (see Table III.A-4, Column 3). e CWPDA: See III.A 10/12/99 Page 3