Relationship of Impoundment to Water Quality

Abstract

Among the many things that affect water quality is impoundment. Water quality may be improved or degraded by impoundment. This article discusses some of the more significant beneficial and detrimental effects of impoundment and the principal factors causing changes in water quality. Important beneficial effects of impoundment on water quality include: reduction of turbidity, silica, color (in certain reservoirs), and coliform bacteria; evening out of sharp variations in dissolved minerals, hardness, pH, and alkalinity; reductions in temperature, which sometimes benefit fish life; entrapment of sediment; and, storage of water for release in dry periods for the dilution of polluted waters. In addition to benefits, impoundment also has certain undesirable effects, including: increased growth of algae, which may give rise to tastes and odors; reduction in dissolved oxygen in the deeper parts of the reservoirs; increase in carbon dioxide and frequently iron, manganese, and alkalinity, especially near the bottom; increases in dissolved solids and hardness as a result of evaporation and dissolution of rock materials; and, reductions in temperature, which, although sometimes beneficial, may also be detrimental to fish life.

Water quality characteristics of regulated rivers

“…Reservoirs located on saline rocks may achieve particularly high solute levels during their early years of formation. The salinity of outflows from Lake Mead, Nevada, USA, for example, was greater than that of the inflows during its first 15 years of existence, due to the dissolution of large quantities of gypsum and rock salt (Love, 1961).…”

Limnology of tropical impoundments: a comparative study of the major reservoirs in Madras State (India)

“…According to LOVE (1961), damming up results in the reduction of turbidity, silica, colour, temperature, etc . evening out sharp variations in dissolved oxygen, minerals, hardness, pH and alkalinity and in the entrapment of sediments .…”

“…Since large volumes of water are continuously discharged from impoundments, their value in pollution abatement is immense . INGOLS (1957), LOVE (1961), SYLVESTER (1958), REID (1961) and SYMONS et al . (1965) on the other hand feel that the downstream water is low in oxygen and will affect the purification processes.…”

CHANGES IN WATER QUALITY IN THE NEWLY IMPOUNDED SUBTROPICAL FEITSUI RESERVOIR, TAIWAN1

“…The construction of a reservoir converts an existing river into a man-made lake. Environmental alterations make the water quality change frequently, indicating unstable conditions during the incipient operational period (Balon and Coche, 1974;Love, 1961;Petts, 1988). Besides polluted inflow water (external point and nonpoint sources), submerged vegetation and disturbed topsoil in the flooded area are recognized as dominant factors that cause reservoir eutrophication during the incipient operational period (McLachlan, 1971;Hecky, 1984;Filip and Manojlovic, 1993).…”