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<br />o <br />to <br /><.0 <br />00 <br /> <br />in decreasing salinity. Other possible factors are <br />man made or natural alterations in the salt load <br />producing areas of the basin. At a given point in <br />the system, a systematic change might manifest <br />itself as a shift in the solute concentration- <br />streamflow relationship or in the absolute or <br />relative solute load. <br /> <br />Research Objectives <br /> <br />As a first step in evaluating the possibility of a <br />systematic change, the present study was initiated <br />. with the following objectives: <br /> <br />1. Create a data base that includes average month- <br />ly streamflows and major solute concentra- <br />tions at selected gaging stations in the <br />Colorado River Basin <br /> <br />2. Develop a theoretical model for the relation- <br />ship between streamflow and individual <br />solute concentrations <br /> <br />3. Identify significant long-term trends in solute <br />concentration, load, and mass fraction for <br /> <br />USGS <br />number <br /> <br />90955 <br />91525 <br />91800 <br />91805 <br />92170 <br />92345 <br />92510 <br />93020 <br />93065 <br />93150 <br />93285 <br />93795 <br />93800 <br />94025 <br />94215 <br /> <br />the period before the construction of major <br />upstream dams <br /> <br /> <br />4. Identify significant changes in the solute <br />concentration, load, and mass fraction after <br />the accelerated reservoir development of the <br />early 1960's <br /> <br />Fifteen stations were selected for analysis(table 1). <br />These are all principal stations used to define <br />concentration-streamflow relationships in the <br />USBR's Colorado River Simulation System. Except <br />for the station on the Duchesne River and those <br />below Lake Mead and Flaming Gorge Reservoir, all <br />had adequate water quality records for the planned <br />statistical analyses. <br /> <br />This report describes the procedures used to <br />develop the data base and presents the results of <br />the statistical analyses. It includes an evaluation of <br />the selected statistical procedures based on the <br />ease of interpreting their results. A cursory inter- <br />pretation of the results and their implications for <br />the salinity control program is also given, though a <br />more complete analysis is recommended. No <br />attempt is made to reconcile the recently observed <br />TDS at Imperial Dam with earlier projections. <br /> <br />Table 1. - Colorado River Basin gaging stations selected for analysis <br /> <br />Period of <br />record' <br /> <br />Colorado River near Cameo, Colorado <br />Gunnison River near Grand Junction, Colorado <br />Dolores River near Cisco, Utah <br />Colorado River near Cisco, Utah <br />Green River near Green River, Wyoming <br />Green River near Greendale, Utah <br />Yampa River near Maybell, Colorado <br />Duchesne River near Randlett, Utah <br />White River near Watson, Utah <br />Green River at Green River, Utah <br />San Rafael River near Green River, Utah <br />San Juan River near Bluff, Utah <br />Colorado River at Lees Ferry, Arizona <br />Colorado River near Grand Canyon, Arizona <br />Colorado River below Hoover Dam, Arizona <br /> <br />12/33- 6/79 <br />10/31- 8/82 <br />5/51- 9/82 <br />10/28- 4/83 <br />10/51- 5/82 <br />10/56- 6/83 <br />12/50- 8/82 <br />1/51- 3/83 <br />12/50- 7/79 <br />8/28- 4/83 <br />2/47- 5/83 <br />5/29-10/81 <br />5/27- 6/82 <br />11/25- 3/74 <br />10/40- 4/83 <br /> <br />1 Includes all data necessary for generation of monthly concentrations as described in this report. <br /> <br />Location <br /> <br />5 <br />