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. PART V COLORADO RIVER WATER QUALITY ASSESS~ENT ...... Ul ...... -J Another potential problem is the conflict betl.'een the cold .....ater sport fishery in tailwater streams and the warm water requirements of endan- gered fish further downstream. These are examples of loIater qual iry management alternatives Iohich may be beneficial to one user and detri- mental to another. At present, the policy is multiple use, and Reclama- tion has tried to optimize the greatest overall benefits. 2. Economic and Health Impacts In the Lo....er Basin, present peak TDS concentrations are approaching critical levels for some salt sensitive crops and, l.Ihile suitable for irrigation of most crops, are high enough that special irrigation practices are used in some cases. At the present time, TOS concentrations are being maintained below the standards. Complete development of apportioned water by the States will result in increases in TOS that would be more detrimental to agriculture without salinity control measures. . A consortium of ....ater resources centers in the States of Arizona, California, Colorado, and Utah cooperated in a study funded by the Office of Water Research and Technology and the Bureau of Reclamation to assess the economic damages caused by various salt concentrations to agricultural and municipal water users. This study is documented in a report, Salinit ~anagement 0 tions for the Colorado River, Water Resources Planning Series Report P-78-003, June 1978. 12 Based upon the findings of that report, Reclamation has pub- lished a summary ....orking document entitled, Colorado River Salinity-- Economic Impacts on Agricultural, Municipal, and Industrial Users.rI3} The estimated future annual damaF;es to the LOloler Basin ....ater users in 1976 dollars were S343,OOO.!J for each 1 mg/L increase at Imperial Dam when concentrations reach the range of 875 mg/L to 1,225 mg/L. This damage figure is approximately S513,300.!J per mgfL in 1982 dollars. These annual damages were calculated using the 1972 sal inity standard of 879 mg/L (approved by EPA in 1975) and a projected full development salinity concentration of 1,225 mg/L at Imperial Darn. The annual municipal damages are divided as follo....s: Metro- politan ....'ater District, 54 percent; Central Arizona Project, B percent; and LO\o'€r Mainstem users, B percent. Total agriculture annual damages are 30 percent. Industrial impairments are not separated from municipal cost estimates. . The health impacts of high TDS waters presently are poorlv understood and are a subject of some debate. High suI fate ....aters fre- quently exceeding 500 mg/L for local domestic supplies are known to cause problems in sensit ive people, particularly infants, and to visitors who have not developed a tolerance. High levels of sodium in drinking water supplies may aggravate high blood pressure problems. 1/ damages The annual damages represent impact to users belo. Hoover Dam; from projects located downstream of Hoover Dam ....ill be less. 22