Effects of Impoundments on Water Quality

Changes occurring in the quality of water during its passage through Tennessee River reservoirs and during lengthy storage in tributary impoundments are observed. Seasonal variations of temperatures of water discharged from main-river impoundments are discussed. DO concentrations in the water discharged from main-river reservoirs recede during the summer months but do not reach the low concentrations observed below storage impoundments. Both total coliform and fecal coliform concentrations in main-stream reservoirs increase greatly below local municipalities. In tributary storage impoundments strong thermoclines develop in early spring, and relatively cool water, low in DO, is discharged through low-level power intakes well into or throughout the summer. Low DO concentrations are also caused by biological activity in eutrophic impoundments, inflows to which are otherwise relatively free of pollution. A multiple regression technique is used to develop an equation for predicting DO concentrations to be expected in releases from a proposed impoundment.