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.'"7 .~ .' ~ Colorado River Compact Symposium James S. Lochhead Page 24 of the Law of the River, the Bureau of Reclamation's official estimate of the water available to the Upper Basin is 6.0 maf/yr. The Upper Basin states disagree with this estimate but, as with the Mexican Treaty question, the issue is not yet ripe. As shown on the chart above, total upper Basin use and reservoir evaporation is only about 4.2 maf/yr. at this time. Because of the uncertainty over how much will ultimately be available under the Compact, the Upper Colorado River Basin Compact allocated the entitlement to use water under the Colorado River Compact among the upper Basin states on a percentage basis. Colorado was allocated the entitlement to deplete the river by 51.75% of whatever consumptive use is available to the upper Basin states in any year under the Colorado River Compact. Thus, if the total available to the Upper Basin is 6.0 maf/yr., Colorado may deplete the river by 3.079 maf/yr. If the Upper Basin entitlement is 7.5 maf/yr., Colorado may deplete the river by 3.885 maf/yr. Colorado's current uses are somewhat over 2.6'maf/yr. The Neqotiators Did Not Foresee the Emerqence of Urban Demands and Environmental and Recreational Values The Compact negotiators did predict increasing demands for water in the basin. Much of this was defensive in nature a prediction of future demand served as a justification for a higher claim of entitlement. These predictions, and even the calculations of present use, were based mostly on irrigation demand. Early in the Compact negotiations the Commissioners discussed an allocation formula based on irrigable acreage. At least claims based on irrigable acreage provided some objective measurement of future demand, so as to avoid pure speculation. The negotiators could not foresee the influx of population to the western U.S., nor the shift from rural communities to urban cities. They recognized potential transbasin demands for Los Angeles and Denver, but potential demands for Southern Nevada were considered negligible, and Phoenix and other areas do not appear to have been discussed. In the late 1970's and early 1980's, upper Basin states were concerned about the potential water demands of massive oil shale development, and whether the Compact would adequately accommodate such demands in the Upper Basin. Although there is no longer a push to develop oil shale, these changing economic circumstances illustrate that the Commissioners could not foresee what demands might exist in the future. These changing conditions also underscore Delph Carpenter's