An intensive study of a 3.3-mile reach of the Yockanookany River, including a major tributary, was conducted August 29-31, 1978. The quality-of-water data were collected during a period of generally law streamflow and seasonally high air temperatures. These data show that the quality of water in Yockanookany River was generally good. The dissolved-solids concentrations were less than 50 milligrams per liter, and the concentrations of nitrogen and phosphorus compounds were low. Ammonia nitrogen and total nitrogen concentrations were higher downstream than upstream. Ammonia nitrogen concentrations ranged from 0.10 to 0.40 milligrams per liter and total phosphorous concentrations ranged from 0.14 to 0.43 milligrams per liter at the downstream site. The 5-day biochemical oxygen demand in the river entering and leaving the study reach generally was less than 2.5 and 6.0 milligrams per liter, respectively. Dissolved-oxygen concentrations generally were higher at the upstream site than the downstream site and were at levels that could support aquatic life at both sites. Several water samples collected at the downstream site contained high fecal bacteria densities and there was some evidence of the presence of wastes of human origin. It was determined from a time-of-travel study that the rate of solute travel was 0.15 mile per hour at law streamflow. A peak dye concentration traveled through a 3.3 mile reach of Yockanookany River in 221/2 hours.
