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<br />002280 <br /> <br /> <br />may have far reaching effects on varied physical, biological, and cultural resources in the Grand <br /> <br /> <br />Canyon and on Lake PowelL <br /> <br /> <br />The challenge of any long-term monitoring program is to collect data focused on addressing <br /> <br /> <br />issue,~ of current concern. while being broad based and of .sufficient quality to answer questions <br /> <br /> <br />which may arise in the future while maintaining a reasonable expenditure of resources. It is our <br /> <br /> <br />belief that data from past and existing monitoring programs on Lake Powell can be evaluated to <br /> <br /> <br />identify effects of various aspects of operation of Glen Canyon Dam and, at the same time, <br /> <br />provide valuable information to scientists and managers from a broad variety of resource areas. <br /> <br /> <br />By balancing information needs, resource expenditures, and monitoring program objectives, a <br /> <br /> <br />valuable 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 <br /> <br /> <br />operations such as inflow hydrodynamics, climatological conditions, and the existence and <br /> <br /> <br />structure of Glen Canyon Dam. However, some water quality attributes of Lake Powell and <br /> <br />downstream releases may be affected by certain aspects of the operation of Glen Canyon Dam. <br /> <br />These effects can be 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 <br /> <br />water loss, temperature regime and heat budget, salinity levels, hydrodynamics and mixing <br /> <br />patterns, nutrient and trace element concentrations, and sediment deposition. These <br /> <br />characteristics, in turn, influence the biological resources of Lake Powell and the Colorado River <br /> <br />below the dam. Affected biological components may include primary productivity, algal and <br /> <br />zooplankton abundance and composition, and the dynamics offish populations, waterfowl, and <br /> <br />higher species. The third affected resource category involves social and economic components <br /> <br />03/06/98 <br /> <br />DRAFT <br /> <br />Page 4 of 62 <br /> <br />