The effects of hydropower releases from Lake Texoma on downstream water quality

Impacts of peaking generation on water quality in the tailwater of lake Tex oma, on the Texas and Oklahoma border, were evaluated during summer stratif ication in the lake. Sampling was conducted before, during, and after a dai ly generation cycle with measurements of temperature, dissolved oxygen, iro n, manganese, and turbidity. Temperatures were near 25 degrees C during gen eration, fluctuated 3-4 degrees C during nongeneration, and increased in a downstream direction to near 28 degrees C. Dissolved oxygen concentrations were between 4 and 6 mg L-1 during generation and increased in a downstream direction. During nongeneration, concentrations in the upstream region of the tailwater were near 2 mg L-1 but were between 4 and 10 mg L-1 in the re st of the study area. Maximum concentrations, 6 to 10 mg L-1, were observed prior to the hydrograph peak at each station, suggesting leading edge effe cts of increased flow and aeration as substrate was covered during river st age increases. Concentrations of metals increased in a downstream direction coincident with turbidity increases from near 3 to 25 NTUs, suggesting res uspension and possibly flocculation. Dissimilar patterns were observed for nongeneration when concentrations decreased in a downstream direction while turbidity was relatively constant and lower than generation values, sugges ting settling with decreased flow.