Results of fisheries investigations in Douglas tailwater, August 1987--September 1988

Releases from Douglas Dam during July, August, and early September are characterized by low dissolved oxygen (DO), increased hydrogen sulfide, and until fall 1987, no minimum flow. Studies are underway to improve water quality in the tailwater. A five-year minimum flow demonstration began October 1, 1987. To achieve a 300 cfs minimum flow at Saffell Island, 2.5 river miles downstream from Douglas Dam, one turbine in the 3200 to 4000 cfs range is pulsed for 35 to 45 minutes every four hours. In addition to minimum flow, surface water pumps and oxygen diffusers in front of the hydro unit intakes are being evaluated as ways to increase DO in the tailwater. During this five-year demonstration water quality monitoring and biological investigations will document changes and responses to increased minimum flow and improved water quality. Objectives of the biological investigations are to document: (1) changes, characteristics, and diversity of the fish community of the tailwater using the Index of Biotic Integrity (IBI), (2) spawning locations and movement patterns of sauger in the tailwater, (3) reproduction of sauger and other species in the tailwater, and (4) fisherman distribution and creel throughout the tailwater. 10 refs., 3 figs., 16 tabs.