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I I I I I I I I I I I I I I I I I I I depletions from commercial pumping in the Amity to Lamar segment were those of Colorado Beef and were obtained from the Colorado Beef Substitute Water Supply Plan. The assumption in this study is that LAWMA will not have to replace the November-through-March depletions for Colorado surface rights because the ditches downstream from John Martin Dam usually do not divert during these months. LAWMA recognizes that it will have to replace November-through-March depletions to usable Stateline flow as discussed below. The municipal depletions in this table are estimated at 30 percent of the pumping. The pumping estimates in this table include some relatively small reductions for pumping that occurred through wells that have been decreed as points of diversion or alternate points of diversion for surface rights. Where such reductions have been made, they are consistent with a) the estimated pumping through the wells, b) provisions in the decrees of the Water Court, and c) reasonable allowances for times when the surface rights were in priority. In addition, there was a reduction for about 900 acre-feet of pumping on the X- Y Ranch in 1994 that was fully replaced pursuant to orders from the Division Engineer. For the purpose of determining depletions to usable Stateline flow, LA WMA is planning to rely on the results of the Kansas H-I Model with the Durbin usable flow method and the Larson coefficients. Model scenarios probably can be developed for future use that will separately represent LA WMA' s well pumping to determine LAWMA's replacement obligations. For this feasibility study, results of existing and more simplified scenarios were relied on. These results indicated that the depletion to usable Stateline flow from LAWMA's 1990-94 level of irrigation pumping averaged 7,976 acre-feet annually. This consultant believes this value is a reasonable approximation of what more specific runs of the H-I Model would show. It has been assumed that LAWMA will not be required to replace to the Arkansas River depletions that are caused by well pumping outside of the main stem area. These aquifers are removed from the Arkansas River by considerable distance. The hydraulic connection between them and the Arkansas River, if it exists at all, is not nearly as direct as it is for the aquifers in the main stem area, so the well depletion rates should be much less. Additionally, the data and methodology that are necessary to derive to these depletion rates have not been developed. Since only small amounts of well pumping occur in these outside areas, a replacement obligation for them, if required, would not affect the feasibility of this program appreciably. In all prObability, the owners of these out-of-the-main-stem wells will continue 14