Laserfiche WebLink
<br />Concern for degradation of the ecosystem downstream from Glen Canyon Dam resulted in the <br />formation of the GCES. program in December 1982, and the agreement not to use the uprated <br />capacity of the powerplant until studies and appropriate National Environmental Policy Act <br />(NEPA) compliance was completed (U.S. Bureau of Reclamation 1982), In 1987, Reclamation <br />requested consultation on the existing operation of Glen Canyon Dam which resulted in a draft <br />jeopardy opinion oil August 25, 1987 (consultation 2-21-87"F-23). In 1988, the Department of <br />the Interior directed further studies (GCES Phase II) on low fluctuating flows, and Reclamation, <br />Arizona Game and Fish Department (AGFD), National Park Service, Navajo Nation Natural <br />Heritage I'rogram, and Service developed seven conservation measures that would support the <br />successful completion of both Section 7 consultation and NEPA compliance (U.S. Fish and <br />. Wildlife Service 1990a). <br /> <br />The preparation of an EIS on operations of Glen Canyon Dam was announced July 27, 1989, <br />by the Secretary of the Interior (Secretary), and the cooperating agencies formed an EIS Team <br />with Reclamation as lead. The Service has participated as a cooperating agency and is on the <br />EIS Team. In 1992, the Grand Canyon Protection Act (P.L. 102-575, Title XVIII) was passed <br />directing the Secretary of the Interior to develop alternatives"... in such a manner as to protect, <br />mitigate adverse impacts to, and improve values for which Grand Canyon National Park and <br />Glen Canyon National Recreation Area were established ...." <br /> <br />With guidance from other cooperating agencies, Reclamation selected the MLFF in January 1993 <br />as the preferred alternative for the Draft EIS. Reclamation reaffirmed that choice in their June <br />17 memorandum and proposed two increases in the operating limits and the removal of <br />endangered fish experimental flows from the preferred alternative (U.S. Bureau of Reclamation <br />1994). <br /> <br />OPERATION <br /> <br />From 1963 to 1980, Glen Canyon Dam was operated under the filling criteria. These criteria <br />ended when the dam spilled for the first time in 1980, Since 1980, the objective has been to <br />produce the greatest amount of firm capacity and energy practicable while adhering to the <br />releases required under legislative mandates. Minimum allowable flows were 1,000 cubic feet <br />per second (cfs) from Labor Day until Easter and 3,000 cfs from Easter until Labor Day. <br />Maximum allowable flow was 31,500 cfs. No restrictions existed on daily fluctuations and ramp <br />rates. Historically, daily fluctuations exceeded 12,000 cfs more than 58% of the days, and <br />20,000 cfs 15% of the days. Provisions also were established for system emergencies and <br />system regulation. <br /> <br />Hourly and daily releases were modified in June 1990 when a schedule of research flows was <br />initiated. These flows were for the purposes of allowing the GCES researchers to evaluate the <br />impacts of current and alternative dam operation so on the downstream resources for the EIS. <br />Following the research flows, the Secretary implemented interim operating criteria on November <br />1, 1991, following a 3-month testing of the proposed interim flow criteria. Interim flows were <br />designed to ameliorate the rate of adverse change on downstream resources resulting from past <br />dam operations pending a final decision on permanent long-term operating criteria. These <br />criteria, known as Interim Flows, are still in operation today. <br /> <br />15 December 1994 final biological opinion 2.21-93-F-167 <br /> <br />4 <br />