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<br />b. Salinity <br /> <br />0323J6 <br /> <br />Specific conductance cycles follow an opposite pattern compared to temperature (Fig 15). As <br /> <br />early summer inflows have more influence on the downstream reservoir, water at the penstock <br /> <br />level become.s progr...l:SSiyelymore dilute. Minimum salinity levels are reached concurrently with <br /> <br />maximum temperature patterns; maximum salinity occurs with minimum temperatures. <br /> <br />v. Discussion <br /> <br />A. Value of Existing and Past Monitoring Programs <br />The primary focus of this assessment isto identifY the effects of Glen Canyon Dam's <br />operation on the water quality of Lake Powell and the Colorado River below Glen Canyon Dam. <br />This assessment was based on data from several sources and includes inflow hydrology, Glen <br /> <br /> <br />Canyon Dam release hydrology, measurements of physical water quality parameters from within <br /> <br /> <br />Lake Powell and dam releases, and the results of chemical analyses of water samples collected <br /> <br /> <br />from the reservoir and its releases. These data were evaluated in the context of the history of Lake <br /> <br /> <br />Powell with its initial filling and fluctuating reservoir levels, changing climatic patterns, and <br /> <br /> <br />changing operations criteria. Attention was given to seasonal patterns, operation of non-power <br /> <br />release, structures, and other significant events such as special releases. <br /> <br />Much more data exists than what was readily available for analysis with the short time frame <br /> <br />of this assessment. Some data, such as dissolved oxygen and pH do not exist with sufficient 10ng- <br /> <br />term quality to evaluate over the complete history of Lake Powell, but are valuable for shorter- <br /> <br />term analysis. Other data have only recently been collected and do not lend themselves to historic <br /> <br />comparison. Several aspects of the assessment were frustrated by the lack of consistent data <br /> <br />collection at a regular time interval. Resultant data gaps during significant parts of Lake Powell's <br /> <br />history have subjected some conclusions to inference and speculation. <br /> <br />03/06/98 <br /> <br />DRAFT <br /> <br />Page 30 of 62 <br />