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<br />h - In order to carry out the Brower proposal. additional legislation would be <br />required to negate the constraints of the 1968 Colorado River Basin Project <br />Act. Specifically. these constraints permit annual releases of water from Glen <br />Canyon Dam in quantities greater than 8.23 MAF only if (1) required for <br />lower basin consumptive use. (2) to equalize storage with Lake Mead. or (3) <br />to avoid anticipated spills. Much greater releases would have to be made to <br />empty Lake Powell. <br /> <br />I - With such a radical change in the "plumbing" of the Colorado River reservoir <br />system, it is likely that the Colorado River Compact. the Upper Colorado <br />River Basin Compllct, and the Mexican Water Treaty would be renegotiated. <br /> <br />2 - With respect to the Glen Canyon Institute's concept to drain Lake Powell to elevation <br />3500 feet, the following can be noted: <br /> <br />a - The minimum power pool elevation at Glen Canyon Dam is elevation 3490 feel. It <br />is possible that some power production could occur at this elevation but there <br />would be the possibility of a vOl1ex. since the centerline of the powerplant <br />penstock is 3470 feet, As shown on the attached reservoir capacity allocation <br />sheet, the lake has a total volume of5,9 MAF at this elevation, From our area- <br />elevation curves, the lake has an area of about 52.000 acres, 32 percent of the <br />maximum area of 161,000 acres, <br /> <br />b - The release capacity of the outlet works is about 15,000 cfs with a gate opening of <br />about 60 percent at the nlll pool elevation of3700 feel. While this amount ~ be <br />released at elevation 3500 feet. a gate opening of 100 percent is required to <br />achieve this release, This may be questionable from a maintenance point of view <br />since at 100 percent gate, the velocities in the outlet tubes currently causes severe <br />cavitation, If restricted to 60 percent gate, the capacity at elevation 3500 feet is <br />about 11,600 cfs, <br /> <br />Powerplant release capacity is unclear under this concept. but existing rating <br />curves suggest that about 30,000 cfs could be released at elevation 3500 feet. <br />About 900 megawatts of cllpacity are llvailable at this level, a reduction of <br />about one-third from the currellt maximum capacity due to the lower head. <br />While powerplant bypasses would be eliminated. energy production would also be <br />reduced, <br /> <br />b - Routings of several magnitudes of intlow were performed to evaluate the amount <br />of unintended storage that would temporarily accumulate in Lake Powell due to <br />the routing effect, With the uncertainties of release capacity, the combined <br />powerplant/outlet works capacity was assumed to be about 45,000 cfs. An <br />examination of historic Lake Powell inflows showed that 45.000 cfs was <br /> <br />7 <br />