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Table 2 - Water Yield Simulation of the South Platte River Between Kersey and Julesburg: With Wells and Without Wells Comparison for Average Year 1975 - 1994 (1,000 at) 0 N 0 J F M A M J J A S Total (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13\ (14) (15) [8] Diversions To Storage With Wells .69.4 -66.2 -46.1 -34.3 -35.6 -48.0 0.0 0.0 0.0 0.0 0.0 0.0 -299.6 [9] Diversions To Irrigation With Wells 0.0 0.0 0.0 0.0 0.0 0.0 -50.2 -75.2 -89.8 -95.6 -89.8 -71.7 -472.2 [10J Well Diversions -52.6 -43.6 -36.6 -32.3 -28.7 -26.6 -23.4 -26.8 -32.7 -40.1 -49.3 -59.2 -451.9 [11] Total -122.1 -109.8 -82.7 -66.6 -64.3 -74.5 -73.6 -102.0 -122.6 -135.6 -139.1 -130.9 -1223.8 [12] Irrigation Returns With Wells 62.6 58.9 54.9 49.4 37.2 30.0 29.0 33.5 33.1 45.9 55.1 61.0 550.7 [13] Returns From Other Sources 26.0 26.0 26.0 26.0 26.0 26.0 26.0 26.0 26.0 26.0 26.0 26.0 312.0 [13a] Total Returns 88.6 84.9 80.9 75.4 63.2 56.0 55.0 59.5 59.1 71.9 81.1 87.0 862.7 [14J Simulated S. Platte River @ Julesburg 19.8 31.0 51.2 59.7 48.3 41.9 39.3 80.3 95.7 -8.0 -16.1 1.9 444.9 [15] Observed S. Platte River @ Julesburq 25.6 23.4 32.9 50.2 50.1 44.3 42.0 75.9 60.8 21.3 12.5 23.1 462.3 Table 3 - Simulated Replacement Water Requirements in the Kersey To Julesburg Reach of the South Platte River (1,000 at) Year 0 N 0 J F M A M J J A S Total 1975 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 76 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.4 0.0 0.0 6.4 77 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.4 16.4 12.8 28.9 25.1 90.6 78 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.7 10.2 9.5 21.4 79 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 10.1 10.1 1980 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.9 6.7 9.6 81 25.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.3 21.8 31.5 31.1 118.7 82 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 26.1 8.4 34.5 83 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 84 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1985 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 3.2 0.0 3.2 86 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 87 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.8 15.8 21.6 88 4.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.9 3.9 12.0 21.0 89 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.8 6.0 16.8 25.1 16.9 70.6 1990 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.1 11.5 23.9 16.2 52.7 91 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.5 18.4 8.6 34.5 92 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.6 0.0 6.4 16.0 93 26.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8.3 16.0 0.0 51.2 94 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.3 5.8 18.6 15.0 18.3 65.0 Mean 2.8 0.0 0.0 0.0 0.0 0.0 0.0 1.0 1.9 5,8 10.5 9.3 31.4 Std. Dev. 7.98 2.52 4.30 7.22 11.42 9.13 33.62 DISCUSSION AND CONCLUSIONS The current regulation of wells in the South Platte River Basin is by no means consistent with the scientific lit- erature. The literature, including this study, has shown that a requirement that wells in existence in 2002 have in place each year a 50-year recurrence interval supply of water each year to augment depletions is not realistic (see Figures 7 and 8). In 2002, one of the driest years in the past fifty, the apparent encroachment by wells was approximately -80,000 af (Figure 7). It should be noted that according to available data, Groundwater appropriators of the South Platte (GASP) and Central Colorado Water Con- servancy District (Central) had the combined capacity to very nearly meet a need of this magnitude during the driest years with modest recharge and surface water supplies (Leaf, 2002). Today, GASP has been eliminated and Central is on the verge of being eliminated. In addition to the quantity of replacement water that is necessary to restore the river, at least two other issues have emerged. First is the issue of apparent well deple- tions and consequent encroachment during November- April on senior reservoir rights. According to this study, there is apparently no significant hydrologic impact of the wells during the winter months (Table 3). The final issue concerns lag times in the basin. It is Page 7