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4 UDENWLR 290 4 U. Denv. Water L. Rev. 290 (Cite as: 4 U. Denv. Water L. Rev. 290) Page 14 Table II: Comparison of Consumptive Uses, Losses, and Water Supply TABULAR OR GRAPHIC MATERIAL SET FORTH AT THIS POINT IS NOT DISPLAY ABLE Table II Notes TABULAR OR GRAPHIC MATERIAL SET FORTH AT THIS POINT IS NOT DISPLAY ABLE *319 Bi3'eause of the delivery obligation in Article lII(d) of the Compact, the burden of the forecasted supply deficiency falls ditectlyon the Upper Division States. If the Upper Basin has a ftrm obligation to allow a ten-year average of 7.5 m.a.f. to go to the Lower Basin each year, this obligation limits its use to what remains in the Colorado River. The amount left depends upon hydrologic cycles. Based on its hydrologic analysis and interpretation of the Law of the River, the Bureau of Reclamation's d.fticial estimate of the water available to the Upper Basin is only 6.0 m.a.f.l.yr. The Upper Division States disagree with this estimate, but the issue is not yet ripe since Upper Basin depletions remain below this amount. As shown on the chart above, t~wJUpper Basin use and reservoir evaporation is only about 4.7 m.a.f.Iyr at this time. (FN1261 Because of the uncertainty about how much water will ultimately be available under the Colorado River Compact, the Upper Colorado River Compact allocated the entitlement to use water under the Colorado River Compact among the Upper Division States on a percentage basis. Therefore, unlike the Lower Division States whose allocations are ftrm, the allocation of each Upper Division state is uncertain and variable. For example, Article I1I(a)(2) of the Upper Colorado River Compact entitled Colorado to deplete the Colorado River by 51.75% of the available Upper Basin consumptive use in any year. [FN1271 ~s;if the total available to the Upper Basin is 6.0 m.a.f./yr, Colorado may deplete the Colorado River by 3.079 m.a.f.Iyr. [FN1281 If the Upper Basin entitlement is 7.5 m.a.f./yr, Colorado may deplete the *320 Colorado River by 3.885 m.a.f.Iyr. [FN1291 Colorado's current uses are about 2.5 m.a.f./ yr. [FN1301 B..~ompact Negotiators Left Umesolved Issues Because of their water supply estimates, the negotiators thought they left some room in which to work. The n~-gotiators based their discussions on what they felt were the reasonable water supply needs in each basin--7.5 m.a.f./yr--and gave the Lower Basin an additional million acre feet to allow for Lower Basin tributary use. Because they had not allocated all the water in the Colorado River, they felt that extra water remained for some intentionally umesolved issues. For example, the negotiators provided in Article lII(c) that the states would handle any obligation to deliver water to Mexico under a treaty by using water surplus to that allocated under Article lII(a) and (b). Ifno surplus exists, the Upper and Lower Basins are to share equally in meeting any such deficiency. The Lower Basin argues no such surplus exists, and the Upper Basin therefore has a delivery obligation. Thus, in addition to its 75 m.a.f. delivery obligation, the Upper Basin potentially faces the added burden of contributing oBe~half of the 1.5 m.a.f. Mexican Treaty obligation, and possibly the transit losses between Lee Ferry and the Mexican border. However, the Upper Basin States assert thl.W"are under no obligation to contribute any water to Mexico. They argue that since the total Lower Basin consumptive use has exceeded its total apportionment of 8.5 m.a.f./yr, the Lower Basin is using sUl'plus water, and must reduce its consumptive use to 8.5 m.a.f./yr before the Upper Basin can have any obligation. The chart above shows Lower Basin mainstem consumptive uses of 8.0 m.a.f./yr. If one adds in Lower Basin tributary uses, even deducting for groundwater overdraft, total Lower Basin consumptive use is currently in excess of its 8.5 m.a.f./yr allocation. The Upper Basin States argue this excess use eliminates any burden the Upper Basin might otherwise have toward Mexican Treaty deliveries. Resolution of the question may depend on how the Compact accounts for Lower Basin tributary use. [FN1311 The Compact, in Article VII, does not explicitly resolve the question of Indian reserved rights--how much they are, or their priority. [FN1321 In Arizona v. California, the United States Supreme Court answered that question for five Lower Basin Indian tribes, adjudicating *321 to them reserved rights totaling 900,000 acre-feet. [FN1331 The Court's decision also made clear that in the Lower Basin, use of mainstem water is charged against the allocation of the state in which the consumptive use of that water is made. [FN1341 However, both the Upper and Lower Basins have not quantified Indian reserved rights of potentially enormous magnitude. Thus, the impact of this quantification is still unknown. ~~The Negotiators Did Not Foresee the Emergence of Urban Demands and Environmental and Recreational Values The Compact negotiators did predict increasing demands for water in the basin. Much of their predictions were defensive in @ 2006 Thomson/West. No Claim to Orig. U.S. Govt. Works.