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USGS1974

Invertebrate macrobenthos of Lake Oahe, 1968-69

The benthos in Lake Oahe, as determined from about 450 bottom samples collected during the open water season in 1968 and 1969, was dominated by oligochaetes and chironomids; Caenis (Ephemeroptera) and Chaoborus (Diptera) were occasionally abundant. Total benthos was estimated at 3,600 organisms/mA? with an ash-free dry weight of about 2.2 g/mA? (about 33 kg/hectare dry weight). Estimated biomass was 1.3 g/mA? (about 18.5 kg/hectare dry weight) and depths of 0.5-10 m and 3.5 g/mA? (about 52.5 kg/hectare dry weight) at greater depths.

Technical Paper↗

USGS1974

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.

Technical Paper↗