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~ w 0) .-I C '_ 1969. Its purpose was to brief the SWRCB on Colorado River salinity problems. The Chief Engineer gave presentations on the historic and current conditions and de- velopments on the Colorado River, especially as they relate to salinity of Colorado River water. Each of the California agencies that use Colorado River water gave presentations on the adverse effects of salinity. The Chief Engineer also gave a presentation on the in- terstate aspects of the salinity of Colorado River water. Other speakers were from the Federal Water Pollution Control Adminis- tration, the Bureau of Reclamation, the In- ternational Boundary and Water Commis- sion, and the Department of Water Resources. Mr. Kerry Mulligan, Chairman of the State Water Resources Control Board, stated there was need for a report on Colorado River salinity problems and possible solu- tions. Since the Colorado River Board had already commenced studies in January 1969 for a report on Colorado River salinity prob- lems, it was agreed at the meeting that the Board was the proper agency to prepare the necessary report. A memorandum of under- standing between the State Water Resources Control Board, the Colorado River Board, and the Department of Water Resources was later agreed upon, and July 1970 was estab- lished for completion of the report. Salinity Reporting at Imperial Dam The Board staff noted that in the past few. years the reporting of total dissolved solids in Colorado River water near Imperial Dam by the United States Geological Survey, the California Department of Water Resources, and the Imperial Irrigation District was dif- ferent. During the 1967 and 1968 calendar years the values reported by the USGS were in the order of 70-80 ppm less than the values reported by the other two agencies. The Colorado River Board suggested that the agencies meet and agree on identical tech- niques that can be used by all agencies in order to eliminate these differences. Representatives of the Board and of the three agencies met on May 27, 1969, at Im- perial, California. It was found that each agency uses a different method to determine total dissolved solids and that each of the methods are currently accepted and recog- nized by water chemists. The Imperial Irri- gation District evaporates a filtered sample of water and dries the residue at 105'C. The Department of Water Resources follows a similar procedure, except that the residue is dried at 180'C. The United States Geological Survey determines each of the individual constituents and uses the summation of the individual constituents as the total dissolved solids. Dr. C. A. Bower, Director of the United States Salinity Laboratory at Riverside, Cali- fornia, stated that a fourth method of deter- mining total salinity used by the Salinity Laboratory was more accurate and more per- tinent to relating the total dissolved solid content of waters to soil and crop conditions. The Salinity Laboratory's method is based on the summation of the individual constitu- ents, as per the USGS, but it uses the total value determined for bicarbonates rather than one-half the value of bicarbonates as the USGS uses. In view of the need for greater uniformity in reporting salinity, United States Geologi- cal Survey representatives agreed that in ad- dition to reporting the total dissolved solids by the summation method they would also use the residue method with drying at 180'C for all stations to be used for collection of data for establishment of salinity standards. Salinity at International Boundary The fourth year of operation under the five-year agreement between the United States and Mexico embodied in Minute No. 218 ofthe International Boundary and Water Commission was completed on November 15, 1969. Minute No. 218 provides that at Mexico's request the highly saline pump- drainage discharge from the Wellton- 41