Physical and chemical characteristics of Lake Oahe, 1968-69

The physical and chemical characteristics presented provide a description of Lake Oahe and establish bases for certain characteristics which may alter as the reservoir ages. Water temperatures were strongly influenced by wind-driven currents and water depth. The duration of thermal stratification varied from about 3 wk in the upstream portion of the reservoir to about 15 wk near the dam in 1968 and from unstratified upstream to about 15 wk downstream in 1969. Dissolved oxygen was usually near saturation, although it fell to 30% in 1968 and 43% in 1969. Nitrate nitrogen and soluble phosphorous were present on all sampling dates in 1969. Silica levels may have become limiting for diatoms in late summer, 1969.