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. PART V COLORADO RIVER WATER QUALITY ASSESSMENT waters containing blue-green algae ""ill lncrease 1n the future unless c arrec t ed . >- Ul ...... U Providing adequate selolage treatment facilities to keep up with groloith 15 usually a problem in small communities affected by the energy development boom. Such communities typically receive growth impacts during construction and development, and before the production and estab 1 ishment of a tax base. a prahl em intensi fied by the reduct ion of Clean Water Act 201 construction grant funds. 3. Colorado(4} ThE' most significant water quality problem 1n the basin in Colorado is to maintain the existing high quality waters that are threat- en~ by ...'astewater from growing communities. Ammonia, in the un-ionized form, is found in municipal wastewater and IS toxic to aquatic life. Increasing population in the basin brought about by grolo'th in the recrea- tion and energy sectors of the economy is placing a burden on several threatened tributaries as well as increasing waste discharges in the Roaring Fork, Eagle, Fraser, East, and San Miguel Rivers. Tributaties that have sholo'l1 a low degree of impairment owing to ammonia from munici- pal or industrial wastewater include the Crystal River, Gore Creek, Dolores River and lower Colorado River within the State. . Headwater streams in the basin that are located in the Colorado mineral belt frequently are contaminated with heavy metals. Drainage from inactive mine tunnels, mill wastes, and tailings piles are respons- ible for much of the contamination. The major streams that are impacted within the basin include headwaters of the Eagle, Animas, and Uncompahgre Rivers. Improvements in wastewater treatment from mining operations that discharge to the Dolores River, Slate River, and Tenmile Creek has resulted in corresponding improvement to the quality of those streams. Two new reservoirs nolo' under construction--Ridgway in the Gunnison drainage and McPhee on the Dolores River--will impound a ponion of the heavy metal pollution. The Bureau of Reclamation is monitoring the inflow to these reSetvOHS, and has agreed to install an aeration system to prevent Ridgway Resetvoir from becoming anaerobic, if a con- dition is found which allows heavy metals and trace elements to re-enter the water in solution. Depending on the biological availability of the pollutants from the sediments into the food chain, the fisheries--or at least the edibil- ity of the fish flesh--may be impaired in Ridgway Resetvoir and, to a lesser extent, possibly in McPhee Resetvoir. If these reservoirs act as permanent traps for heavy metals, downstream water quality could benefit. . 1'1&1 water from the Dallas Creek Project's Ridgway Resetvoir will be provided by exchange from irrigation for a higher quality source to reduce the impacts from metal pollutants. 17