Physical and Chemical Profiles in Lake Texoma (Oklahoma -Texas) in Summer 1982 and 1983

Lake Texoma, a large, relatively shallow reservoir on the Oklahoma -Texas border, is stratified in late summer. In summers of 1982 and 1983 we made weekly determinations of vertical physicochemical profiles and fish distribution at rive stations in the main deep basin of the reservoir. This part of the reservoir, formed by the junction of the Red River and Washita River arms of Lake Texoma, has a distinct at which there is characteristically a sharp decrease in oxygen and pH, and an increase in specific conductance. In contrast to many natural lakes, Lake Texoma exhibits a gradual decrease in temperature from surface to bottom, without an abrupt thermocline. Although the basic pattern of stratification was similar from July to early September in both years, there were important differences between years in the depth of the chemocline (defined as depth in meters at which dissolved oxygen dropped below 2.0 ppm). Depth of the chemocline also differed substantially among stations on some of the sampling dates. During stratification in both years, the hypolimnion was anoxic. In both years during maximum stratification fish were concentrated in a few meters of the water column immediately above the chemocline. The vertical location of the chemocline, and the resultant position of the epilimnion and hypolimnion, can be critical factors in plans for withdrawal of water from the reservoir or for fish management.