The action is technically feasible, but would cost a
significant amount of money. Reclamation has not studied how that could best be done, and does not intent to spend funds to conduct such a study unless directed by Congress or the Secretary. In the absence of authority
to undertake such an action (following question), it would be inappropriate to spend money on such a study.
The proposal would obviously require an Environmental Impact Statement to comply with NEPA and consultation
to comply with the Endangered Species Act. Impacts related to the Clean Water Act and other legislation would also have to be studied.
Such a proposal would also require legislation to allow Lake Powell to be drained,
either for the Brower proposal to completely drain or for the Glen Canyon Institute to drain to minimum power head. Current operation is in compliance with the Colorado River Basin Project Act of 1968 (PL 90-537). Also,
draining the reservoir would make it difficult to comply with the Colorado River Project Act of 1956 (PL 87-485).
* Can Lake Mead handle the storage which would be necessary if Lake Powell were drained?
The
long-term answer is no. Lake Mead probably cannot handle the consumptive uses of the Colorado Basin, even for the scenario of present Upper Basin storage. The inability to meet this need will especially be the case when
the Upper Basin of the Colorado River is at full development, per the Colorado River Compact of 1922 and the Upper Colorado River Basin Compact of 1948.
By the terms of the 1922 Compact, the Upper Basin States
guaranteed delivery of 75 maf in any ten-year period. Drought periods during the 1930's, 1940's, 1950's, and 1960's recorded annual flows at Lee Ferry of less than 7.5 maf with a low of 4.4 maf in 1934. Without the
carry-over storage in Lake Powell available during such times, existing uses in the Upper Basin might be curtailed in similar droughts. Without Lake Powell storage, dependence on the Colorado River to sustain future
growth and economic viability would subject such growth to great risk of drought and economic hardship. Essentially, the four Upper Basin States would be subject to a water call on the river by the Lower Basin States.
General Information Concerning Glen Canyon Dam Values and Benefits
* Over 3,500 gigawatt-hours of electrical energy used in both the Upper and Lower Basin States would be lost.
* Recreational benefits
associated with Lake Powell total about 3 million visitor days per year. There are significant economic impacts associated with the loss of this recreation industry.
* The reservoir fishery would be lost.
* The cold-water trout fishery below the dam would be lost.
* Current operations of the dam provide for stable and predictable white-water river running activities during periods of high runoff (flows greater than
45,000 cfs for 6 to 10 weeks) and during periods of drought or low runoff.
Additional points of interest related to the Glen Canyon Institute proposal to drain Lake Powell to minimum power head and maintain at that
elevation (el 3,500):
* The proposal would leave approximately 6 maf of storage in Lake Powell, of which about 2 maf would be dead storage. The 4 maf of active storage capacity would be required to maintain minimum
power head and would only be useable to meet downstream demands if the power system were shut down.
* Only present levels of use of Colorado River waters could be maintained without significant and extreme risk to
both water supply and power supplies. About 1.7 maf of future use of Colorado River water would have to be forgone in the Upper Basin.
* Power generation at Glen Canyon Dam would be reduced by a significant amount,
possibly about 30%. Power generation at Hoover Dam would increase some lesser amount, with the net system energy production showing a reduction.
* Twenty miles of stream channel would be recovered in each of the
Colorado mainstream and San Juan River drainages. Approximately 15 miles of the Escalante River would be recovered. Some of this benefit would be lost in years of above average runoff as the runoff is temporarily stored
at Lake Powell due to insufficient release capacities (45,000 cfs). As much as 70 feet of vacated reservoir space would be required to pass the runoff experienced in 1983 or 1984 (resulting peak reservoir elevation
would be 3570 feet).
* Evaporation at Lake Powell would be reduced by about 65% (about 320,000 af), but evaporation would increase by 9% (70,000 af) at Lake Mead, leaving a net decrease in evaporation of 20% (250,000
af) of the total system evaporation.
