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<br />002381 <br /> <br />Lake Powell. <br />The challenge of any long-term monitoring program is to collect data focused on addressing <br /> <br />issues of current concern while being broad based and of sufficient quality to answer questions <br /> <br />which may arise in the future while maintaining a reasonable expenditure of resources. It is our <br /> <br />belief that data from past and existing monitoring programs on Lake Powell can be evaluated to <br /> <br />identify effects of various aspects of operation of Glen Canyon Dam and, at the same time, provide <br /> <br />valuable information to scientists and managers from a broad variety of resource areas. By <br /> <br />balancing information needs, resource expenditures, and monitoring program objectives, a valuable <br /> <br />evaluation tool for future adaptive management may be maintained. <br /> <br />C. Affected Resources <br /> <br />Many processes in Lake Powell are influenced by factors not directly related to dam operations <br /> <br />such as inflow hydrodynamics, climatological conditions, and the existence and structure of Glen <br /> <br />Canyon Dam. However, some water quality attributes of Lake Powell and downstream releases <br /> <br />may be affected by certain aspects of the operation of Glen Canyon Dam. These effects can be <br /> <br />evaluated from data developed in existing monitoring programs. <br /> <br />Three main interlinked resource categories may be affected by the operation of Glen Canyon <br /> <br />Dam and.other factors. Physical and chemical conditions in Lake Powell address evaporative water <br /> <br />loss, temperature regime and heat budget, salinity levels, hydrodynamics and mixing patterns, <br /> <br />nutrient and trace element concentrations, and sediment deposition. These characteristics, in turn, <br /> <br />influence the biological resources of Lake Powell and the Colorado River below the dam. Affected <br /> <br />biological components may include primary productivity, algal and zooplankton abundance and <br /> <br />composition, and the dynamics of fish populations, waterfowl, and higher species. The third <br /> <br />affected resource category involves social and economic components such as power production, <br /> <br />06/02/98 <br /> <br />DRAFT <br /> <br />Page 4 of 62 <br />