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18 ".". ~.. ""., HYDROLOGIC AND HUMAN ASPECTS OF THE 1976-77 DROUGHT Water for Recreation itself naturally. Oxygen sags were reported in Minnesota and California. Higher water temperatures are associated with low streamflows and shallow depths. Aquatic growths may increase; fish, particu- larly trout, may die; evaporation from water surfaces will increase, and the efficiency of water-cooled systems is impaired when water temperatures increase. Water for Fisheries Fishery resources are important economic factors in many regions of the United States, and low stream flows resulting from drought conditions can cause serious problems to the fish popUlations. A few problems are men- tioned briefly below. The combination of low streamflow and very low temperatures in the eastern part of the country increased the ice cover on streams and farm ponds and resulted in fish kills. A similar result occurred when high tempera- tures in several streams in Idaho and in the Trinity River in California occurred in 1977. Hydroelectric power generation was suspended at Trinity Dam so that cooler water could be released from lower levels of Clair Engle Lake to preserve the fishery. The level of Lake Tahoe, Calif., dropped below the outlet chan- nel and part of the Truckee River dried up. There was a reduction in the fish population locally, but no fish kill because the fish moved downstream and adjusted to the reduced flow. there (California Department of Fish and Game, oral commun., 1978). To protect several races of salmon and steelhead trout from near extinction, special flow releases and spills were made in 1977 at dams in the Columbia River basin to augment the low flows and move the juvenile salmonids more rapidly to the ocean. See page 59. Operations at four reservoirs in northern Cali- fornia were altered to provide the best water temperatures possible and to stabilize the flows during the salmon spawning seasons. There are no facilities on many Pacific Coast streams to enhance flow conditions for fish; therefore, the number of fish that could successfully spawn was reduced. This con- dition will affect the fisheries for at least several years (California Department of Water Resources, 1977c). Water-based recreation is a major activity considering the number of people involved and the economic value to many areas. Skiing, boating, fishing, swimming, and water skiing are pursuits that use water directly, and camps or homes around lakes or along streams are enhanced by the aesthetic values of water. Skiers and ski resort operators were among the first to feel the effects of the drought. Low snow depths and a short season made most skiing only fair at best. Also, warmer than usual weather in the Sierras hampered the pro- duction of snow by machines, and resorts with equipment to move snow onto the ski slopes and to pack it did so even though this proce- dure was costly. The lack of patronage and the short season were enough to cause several resorts to declare bankruptcy. Boaters and marina operators had drought related problems during the summer and fall of 1977 when water levels in reservoirs were drawn down to such an extent that marinas were stranded long distances from the water. Temporary expedients were needed to provide launching facilities. Obstacles to boating were exposed in some lakes, and white-water boaters in kayaks or rafts found more rocks showing than usual because of the low stream- flows. Scheduled float trips were canceled; and trips by individual parties were about half the number in 1975. A number of recreational areas in parks and forests were closed to vacationers because of lack of water or because the fire hazard was too great. The ban in northern Minnesota came just prior to the hunting season, and resort owners were faced with a large number of canceled reservations. Water for Navigation Major navigation problems did not develop because of drought-induced low flows. Ade- quate flows were maintained on the Missouri River by releasing water from the main stem reservoirs. Low flows in 1976 on the upper Mississippi River were the reason that pleasure boat operators were requested to reduce their use of locks because the long time necessary to fill the locks delayed other traffic. Shoal- ing and dredging on the lower Mississippi River were very much like numerous other years