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1 Table 7.. Net water available for energy and irrigation under different supply and institutional assumptions (AF x 103). 1975 w l\) ~ ~r;;,. State Net Sta te Sharea Net c Available Consumpti ve Useb Case 1 Colorado New lIfexico Utah Wyomin9 3195 695 1420 864 604 97 156 41 2591 598 1264 823 CASE 2 Colorado New r,1exico Utah Wyoming 3069 668 1363 830 Same 2465 571 1207 789 CASE 3 Colorado New Mex i co Utah Wyoming 2702 589 1202 732 Same 2100 492 1046 649 CASE 4 Colorado New Mexi'co Utah Wyoming 2577 561 1145 697 Same 1973 464 989 656 CASE 5 Co 1 orado New Mexico Utah Wyomi ng 2965 645 1317 802 Same 2361 548 1161 761 1985 2000 Consumptive Useb Net Availab1ec Consumptive Useb Net Availablec 964 125 308 144 2231 570 1112 720 1048 125 320 322 2147 570 11 00 542 Same 2105 548 1055 686 Same 2021 543 1043 508 Same 1743 464 894 588 Same 1659 464 882 410 Same 1613 436 837 553 Same 1529 436 825 375 Same 2001 520 1009 658 Same 1917 :520 997 480 a bFrom Table 6 cSums nonirrigation and non-energy consumptive use, i.e.., municipal, industrial, export, etc. Net water available for energy or irrigation use under the case assumptions fa~~_2. This case uses the Upper Coloraao RIver Commission's estimate of 6.5 MAF for the available supply. This is based on 7.5 MAF to the Lower Basin, but no pro- vision for the Mexican Treaty. Case 3. This case is based on the Bureau-otReclamation1s conservative hypothe- sis of 5.8 MAF for the Upper Basin supply. Since it implicitly assumes 8.3 MAF for downstream commitments, the total basin supply is taken to be about 14.1 MAF, After the, 5.8 MAF is apportioned among the Upper Bas in states, nonenergy and nonagr icultural uses are deducted. Case 4. Th is case uses the average virgin-rIOw since the enactment of the Colorado River Compact (1922-1975) of 13.8 MAF, and downs trearn commi tments of 8.3 MAF. The remaining 5.5 MAF makes this the most stringent' case so far as water availability for the Upper Basin. Case 5. The final case uses the same virginrIOW as Case 4, but downstream commit- ments are taken to be 7.5 MAF Basin and 0.05 MAF for Arizona. is made for the Mexican Treaty. for the Lower No provision Only three cases seem to involve criti- cal water supply conditions (cases 1, 3, and 4) and therefore they were selected for use in the model analysis. Water Quality and Legal Aspects Some surface and subsurface flow into the Colorado River contain large amounts of dissolved salts. The salt concentrat ion generally increases from the headwater areas to downstr,eam. The rate of increase'is directly related to the geologic character of the terrain across which the Colorado River and its tributaries flow. In the lower portions of the Upper Basin, there are several areas of shallow shale deposits where the salts are readily dissolved by water movement across or through the soil profile. In addition to the natural loadings, human 16