Chemical and biological water quality in Rattlesnake Creek basin, Ohio, are evaluated. The data include field and laboratory data for eight sites during August 1976- August 1977 and summaries of earlier (1972-76) data.
Streamflow was below normal during the study period. Basin waters types were calcium bicarbonate or calcium magnesium bicarbonate. Specific conductance ranged from 405 to 1,300 micromhos per centimeter. High concentrations of sodium (110-140 milligrams per liter) , nitrogen (24 milligrams per liter as N), and phosphorus (7.8 milligrams per liter as P) were observed during low flows downstream from domestic sewage facilities. Nonpoint sources contributed high concentrations of nitrate-nitrogen to all streams during the high flows of winter and spring.
Dissolved-oxygen concentrations in the upper basin ranged from 3.2 to 18.4 milligrams per liter. Mean saturation values of dissolved oxygen were at or near 100 percent in the lower basin. Stream pH exceeded 8.4 when dissolved-oxygen saturation was above 120 percent. Bacteria and invertebrate data suggest that moderate pollution from cultural sources may exist in the upper basin.
Water quality was poorest in the sluggish flows of the upper basin but improved downstream. Increases in flow velocity and stream aeration rates, dilution, and biological activity contributed to the downstream recovery. Except for' high nitrogen concentrations, water quality was best in the lower basin.
