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<br />:)00073 <br /> <br />Reservoir Studies <br /> <br />.. <br /> <br />A study is currently underway to evaluate the impact that the two major <br />reservoirs, lakes Powell and Mead, have on the salinity of the river system. <br />The study is being conducted under contract to J. E. Edinger Associates and <br />is scheduled for completion in November 1983. They are applying a two- <br />dimensional thermal hydrodynamic chemical equilibrium model to lakes Powell <br />and Mead. The objective of this study will be to track the ion constituent <br />makeup through the reservoir, quantifying any predicted calcite precipitation <br />or gypsum dissolution and evaporation concentration. A generalized predic- <br />tion technique could then be developed for use in the CRSS for applying a <br />corrective factor to the TDS load in lakes Mead and Powell. This study would <br />address a longstanding concern that the CRSS model does not reflect any <br />changes in TDS that the reservoirs may impose on the system. <br /> <br />Solute Trend Study <br /> <br />The Colorado River Water Quality Office is presently funding a 1-year inhouse <br />study to investigate trends in the loadings of individual ions in the Colorado <br />River and its tributaries. This is an attempt to isolate a cause for the <br />apparent change in the relationship of historic data comparing flow to TDS in <br />the post-1965 period. If a physical basis for change can be identified, then <br />the monthly flow-salt coefficients used to develop the "virgin" salt data <br />base from the "virgin" flow data base can be modified, thus providing more <br />confidence in future projections. The study is scheduled for completion in <br />September 1983 and is considered to be a preliminary step in evaluatin9 the <br />need for future constituent ion work in the basin. <br /> <br />FINDINGS <br /> <br />1. There is a growing need for a basin-wide evaluation of potential alterna- <br />tive reservoir operating scenarios which interrelate salinity levels to <br />releases for irrigation, power generation requirements, flood control, <br />recreation, fish and wildlife, and other uses. <br /> <br />2. In our evaluation of the ongoing activities under WQIP, delays have <br />caused slippage in the program. Some of these delays have been beyond our <br />control, and some we have induced ourselves. We have developed and continue <br />to perfect the state-of-the-art knowledge in salinity control efforts; <br />therefore, progress is probably commensurate with our ability to utilize <br />current technology. The WQIP effort should continue without any additional <br />administrative or imposed delays since these measures are needed to meet the <br />TDS numeric criteria salinity standard by the year 2010 under the most <br />prObable hydrology conditions (see comment No. 10). For example, the <br />six units (lower Gunnison Basin, McElmo Creek, Uinta Basin, PVID, Sinbad <br />Valley, and Saline Water Use and Disposal Opportunities Units) being proposed <br />for authorization by the Forum would not all be completed until 1997 even <br />under the best of conditions. <br /> <br />3. Efforts should continue to develop an MOA with BlM and to implement any <br />site-specific cooperative efforts. We also need to cooperate fully with BlM <br /> <br />15 <br />