Potential impacts of a proposed reservoir on hydrologic and water-quality conditions in Little Rush Creek watershed, Fairfield County, Ohio

Water-quality and discharge measurements were made at three sites on Indian Run and one site on Little Rush Creek between February and December, 1979. Indian Run was observed above and below the U.S. Soil Conservation Service Reservoir, VI-D. Little Rush Creek was observed 1.1 miles downstream from the proposed U.S. Soil Conservation Reservoir, VI-A, site. Data from the Indian Run sites were used to predict the potential water-quality conditions in and downstream from the proposed Little Rush Creek Reservoir.

Temperatures measured in Indian Run at the reservoir outflow were as much as 4oc greater than those at the inflow. Dissolved-oxygen saturation ranged from 62 to 110 percent in the inflow and from 57 to 120 percent in the outflow. Indian Run and Little Push Creek are characterized by moderately hard to very hard calcium bicarbonate water. The concentration of dieldrin in water samples from both Little Rush Creek and the outflow from the reservoir on Indian Run was 0.01 micrograms per liter, and in reservoir-surface samples it was 0.02 micrograms per liter. Chlordane concentration in a bottom material sample from the reservoir was 26 micrograms per kilogram. Catfish taken from the reservoir contained 190 micrograms per kilogram chlordane.

All sites showed a good diversity in benthic invertebrate communities. Blue-green algal blooms occurred in the reservoir, indicating nutrient-enriched conditions.

Because of similarities in land use and watershed characteristics, water in the proposed reservoir VI-A is expected to be similar in quality to that of reservoir VI-D. The new reservoir will not significantly affect downstream water quality.