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002277 I. Introduction The Grand Canyon Protection Act of 1992 requires the Secretary of the Interior to evaluate the impacts of Glen Canyon Dam operations on all affected resources. Although the primary evaluation of these impacts are on resources downstream of the dam, concern has existed that certain aspects of dam operations have the potential to affect various resource attributes upstream of Glen Canyon Dam. In January 1997, the Grand Canyon Monitoring and Research Center (GCMRC) presented to its Planning and Transition Work Groups, a prospectus for assessing the effects of Glen Canyon Dam's operation on water quality resources in Lake Powell and Glen Canyon Dam releases (Appendix A). This document will serve to define the scope and objectives of this study, and will form the basis for review of the assessment process and results. Three experienced reservoir limnologists from outside the federal goverrunent not currently connected with GCMRC have provided critical review. Three federal Iimnologists provided additional review from the Bureau of Reclamation and the U.S. Geological Survey. Final results of the assessment will be reviewed by a Science Advisory Group and presented to the Adaptive Management and Technical Work Groups. A. Scope and Objectives of Assessment This assessment is an effort to integrate existing data from current and past monitoring programs on Lake Powell in order to evaluate the effects of various aspects of Glen Canyon Dam operations, from 1965 to 1997, on reservoir and release water quality. Primary consideration will be made to peaking power generation, operation of non-power release structures, and potential selective withdrawal. An attempt will be made to identify other factors affecting Lake Powell such as the existence and structure of Glen Canyon Dam, climatological factors, and internal 03/06198 DRAFT Page 1 of 62