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<br />. <br /> <br />"'"" <br /><::> <br />~ <br />"'1 <br /> <br />.) <br /> <br />. <br /> <br />EVALUATIONS OF EXISTING SALINITY CONDITIONS (continued) <br /> <br />present, except for water quality records during the period November 1944 <br />to September 1950. The water quality for this time period is based on <br />specific conductance records and intermittent chemical analyses. The <br />samples used for the chemical analyses are collected monthly by the Geo- <br />logical Survey stream gaging station below the dam. <br /> <br />Colorado River below Parker Dam, Arizona-California (Station No. 19). <br />Flow records at this station are available from October 1934 and have been <br />published or are available from the Geological Survey. The water quality <br />data for the period January 1964 through December 1970 were taken at the <br />Geological Survey station, Colorado River below Parker Dam. The water <br />quality data for the period January 1941 through December 1963 were based <br />on chemical analyses of Colorado River Aqueduct flows made by the Metro- <br />politan Water District. These data have been adjusted based on a correla- <br />tion of concurrent Metropolitan Water District records with records made <br />by the Geo logi cal Survey be low Parker Dam for the years 1964-70. The <br />correlated data were then used for the period 1941-63. <br /> <br />Colorado River at Imperial Dam, Arizona-California (Station No. 20). <br />Although Figure 2 indicates flow records are available for the report <br />period, a combination of stations was used to obtain the record. Records <br />from January 1941 through September 1942 are from the station, Colorado <br />River near Picacho, California. Records from October 1942 through <br />September 1960 are based on the combined records of discharge obtained at <br />~aging stations on Colorado River at Yuma, All-American Canal near Imperial <br />Dam, Gila Gravity Main Canal at Imperial Dam, Yuma Main Canal at Laguna <br />Dam, and North Gila Valley Canal at Laguna Dam less that of Gila River near <br />Dome, Arizona. Records after September 1960 are based on the comb i ned <br />daily discharge of Colorado River passing Imperial Dam and at gaging <br />stations on All-American Canal near Imperial Dam and Gila Gravity Main <br />Canal at Imperial Dam and the diversion to Mittry Lake. <br /> <br />Quality data from 1943 through October 197D were obtained from Geo- <br />logical Survey records and are based on data for the Yuma main canal <br />below the Colorado River Siphon. The water quality data for November and <br />December 1970 and for calendar years 1971-78 were obtained from the <br />Geological Survey records for the water quality station at Imperial Dam. <br />The samples are presently being collected by the Geological Survey and the <br />Water and Po~er Resources Service above the trash racks at the diversion to <br />the All-American Canal. Salinity analyses are made by the Geological <br />Survey in cooperation with the Water and Power Resources Service. Field <br />analyses and bacteria determinations are made by the Geological Survey in <br />cooperation with EPA. <br /> <br />3. Other Quality of Water Stations <br /> <br />In addition to the key stations discussed above, there are many more <br />points at which water quality data are obtained. Most of these sampling <br />stations are operated by the Geological Survey; however, a number are <br />operated by the Water and Power Resources Service and other Federal, State <br />and private agencies. <br /> <br />41 <br />