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<br />14 <br /> <br /> <br />W <br /> <br />,-'.J_.. <br />(,.;j <br />~ <br /> <br />Professional Paper 442. This report is based on data for the 1941- <br /> <br />1957 period. In summary, the report states that if. the developments <br /> <br />of 1957 had not been in existence then: (1) the hypothetical average <br /> <br />yearly water yield at Lees Ferry would have been about 15.2 million <br /> <br />acre-feet rather than the 12.7 million measured, (2) the hypothetical <br /> <br />average concentration would have been about 250 rng/l rather than <br /> <br />observed values of about 500 mg/l, and (3) the hypothetical dissolved <br /> <br />solids discharge would have been about 5.2 rather than observed amounts <br /> <br />of about 8.7 million tons annually. Substantially all the increase in <br /> <br />dissolved solids discharge was construed by the investigators to be <br /> <br />an effect of irrigation on 1.4 million acres of land. They estimated <br /> <br />the average increase to be 2.4 tons per irrigated acre per year. From <br /> <br />one part of the area to another, this average was said to !ange from <br /> <br />about 0.1 to 5.6 tons. The report did not indicate which portion of <br /> <br />this increase was due specifically to irrigation and which to natural <br /> <br />sources. <br /> <br />Upper Colorado River Basin Cooperative <br /> <br />Salinity Control Study (USBR) <br /> <br />In cooperation with the Federal Water Pollution Control Administra- <br /> <br />tion (now the Office of Water Programs, Environmental Protection <br /> <br />Agency), the Bureau of Reclamation in July 1969 completed a report <br /> <br />entitled "Upper Colorado River Basin Cooperative Salinity Control <br />