Postimpoundment Survey of Water-Quality Characteristics of Raystown Lake, Huntingdon and Bedford Counties, Pennsylvania.

摘要

Water-quality data, collected from May 1974 to September 1976 at thirteen sites within Raystown Lake and in the inflow and outflow channels, define the water-quality characteristics of the lake water and the effects of impoundment on the quality of the lake outflow. Depth-profile measurements show Raystown Lake to be dimictic, with two overturn periods annually--one in the spring and one in the fall. Thermal stratification is well developed during the summer. Generally high concentrations of dissolved oxygen throughout the hypolimnion during thermal stratification, low phytoplankton concentrations, and small diel fluctuations of dissolved oxygen, pH, and specific conductance indicate that the lake is low in nutrients, or oligotrophic. Minor vertical changes in pH were due mainly to variations in the carbon dioxide-bicarbonate-carbonate equilibrium. The comparatively low nutrient content and minimal littoral area tend to reduce the growth of nuisance aquatic vegetation. Algal assays of surface samples indicate that orthophosphate was a growth-limiting nutrient. The settling of fine sediment and a decrease in the phytoplankton biomass result in increasing water transparency from the head of the lake to the dam. Chemical analyses of the lake waters in contact with the bed material indicated no potentially toxic concentrations of metallic ions.