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<br />. <br /> <br />. <br /> <br />. <br /> <br />It-'" <br />..... <br />~ <br />f.,j <br /> <br />SPECIAL STUDIES (continued) <br /> <br />helpful in estimating effects on water quality of return flnws from larger <br />areas where measurement of inflow and outflow is not al'Wsys possible or <br />practical. Studies nf local areas are also conducted under the Section 208 <br />program (Public Law 92-500) or by private organizations under contract with <br />the Government. These 208 studies include the investigations of all <br />sources of salinity, as well as bacteriological, biological. heavy metals, <br />and all other types of pollution. <br /> <br />Special studies in areas of the basin will continue to be made from <br />time to time to determine water quality conditions, and studies of proj- <br />ects, such as Florida, Grand Valley, and Vernal areas should be repeated or <br />continued in order to evaluate changes with time. <br /> <br />G. Environmental Protection Agency Report <br /> <br />A special 1971 report by the EPA entitled "The Mineral Quality Problem <br />in the Colorado River Basin" presents results and recommendations obtained <br />from a comprehensive salinity control study. This report includes a <br />presentation of natural and manmade conditions affecting mineral quality, <br />the physical and economic impacts, and salinity control and management <br />aspects.(20) <br /> <br />H. Model Studies <br /> <br />I. <br /> <br />Colorado River Storage Project Model <br /> <br />This mathematical model was developed by the Water and Power Resources <br />Service for the Colorado River Reservoir Long-Range operating criteria <br />(Public Law 90-537) and includes monthly water supply data for the period <br />1906-74. It does not project future quality conditions at any station <br />above Lees Ferry. Water quality data were added to the model to obtain <br />salt loadings. Since water quality records are not available for the <br />years prior to about 1941, the records back to 1906 were obtained by <br />correlations. <br /> <br />This model was used in the sizing study for Yuma Desalting Plant which <br />has been authorized for construction under Title I of Public Law 93-320. <br />The study shows the magnitude, duration, and frequency of extreme salin- <br />ities in the lower reaches of the Colorado River. <br /> <br />2. Interim Water Quality Simulation Model for the Colorado River <br /> <br />This model was developed by the Water and Power Resources Service in <br />1973, and nominally duplicated the hand computed model shown in Table 18 of <br />the January 1973 "Quality of 'lIater Colorado River Basin Progress Report" <br />No.6, as it included the 1941-70 period of record. The model ("Applica- <br />tion of a River Network Model to Water Quality Investigations for the <br />Colorado River," September 1973 by R.W. Ribbens and R.F. Wilson) however, <br />was different in that it simulated reservoir operations, waS computed on a <br />monthly, year-by-year, instead of an average annual basis and was developed <br /> <br />105 <br />