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<br /> <br />. <br /> <br />..... <br />l\J <br />o <br /> <br />. ., <br /> <br />. <br /> <br />. <br /> <br />QUALITY OF WATER <br />COLORADO RIVER BASI~ <br />PROGRESS REPORT <br /> <br />SL'l1MARY <br /> <br />This biennial progress report presents the various important water <br />quality aspects of the Colorado River. Although several water quality <br />parameters are discussed, the major part of the report is allotted to <br />salinity (total dissolved solids) because it is presently the most <br />serious quality problem on the river system. The historical, present <br />codified. and future salinity conditions of water of the Colorado River <br />down to Imperial Dam are presented In this report. The historical Is <br />represented by a tabulation of the recorded or estimated past condition <br />at 17 quality of water stations for the 1941-74 period. The present <br />modified condition includes adjustments of the historic condition based <br />on the assumption that all developments existing at the present time <br />were in operation for the full 1941-74 period. Estimated future con- <br />ditions are shown for the years 1980, 1990, and year 2000. They are <br />estimated projections after the presently authorized developments, <br />projects proposed for authorization, and other future anticipated projects <br />are placed in operation. <br /> <br />Under historic conditions the average concentration of dissolved <br />solids of the Colorado River at Lees Ferry was about 558 mg/l, below <br />Hoover Dam about 693 mg/l, and at Imperial Dam about 766 mg/1 for the <br />1941-74 period. <br /> <br />Under present modified conditions (that is 1941-74 historical flows <br />modified to reflect present depletions), the concentrations would have <br />been about 610, 751, and 861 ~g/l, respectively, at the three stations. <br /> <br />The projection of future water quality conditions was based on <br />1941-74 averages rather than a year-by-year study. Three models were <br />considered before selecting the averages method. The Colorado River <br />Simulation model was not used because the data base was not completed in <br />time, but it is anticipated that this model will be the one used for the <br />next report. The Colorado River Storage Project model was also considered, <br />but it does not show quality conditions at any of the selected stations <br />above Lees Ferry. The CRSX and CRSP models are further discussed in Part x. <br /> <br />There are SOme l~itations in using a model based on averages since <br />upper and lower limits are not defined and the actual conditions for <br />several years in the future ~ay not truly be represented. <br /> <br />1 <br />