Data collected for a wide range of flow conditions from September 8, 1975, to July 13, 1976, reveal that human and animal waste loading of streams and pesticide use in the watershed are probably the most significant water-quality problems. Generally, the type(s) of water in tributary streams in the south and southwest parts of the watershed was calcium bicarbonate and in other tributaries were calcium sulfate and magnesium sulfate. Dissolved-solids concentrations of discharge from top-spill reservoirs were lower and more consistent over a range of flows than concentrations from uncontrolled streams. Chemical characteristics of discharges from bottom-draw reservoirs differed from those of discharges from the other reservoirs. More than half the manganese concentrations equaled or exceeded 0.05 milligrams per liter, the maximum concentration recommended for domestic water supplies. Leaf fall in forested parts of the watershed are probably a source of this manganese. Nitrate (as nitrogen) concentration of streams ranged from 0.00 to 2.5 milligrams per liter; orthophosphate (as phosphorus), from 0.00 to 0.29 milligrams per liter, and total organic carbon, from 2.0 to 14 milligrams per liter.

Concentrations of fecal coliform bacteria and fecal streptococcal bacteria ranged from 5 to 65,000 colonies per 100 milliliters and from 5 to 24,000 colonies per 100 milliliters, respectively. Occasional human-waste contamination is indicated downstream from the towns of Borden and Speed. Data on periphyton, phytoplankton, and benthic communities collected during low flow in September 1975 indicate organic loading of Muddy Fork downstream from the town of Speed. Phytoplankton community structures varied temporally and spatially.

Ranges of concentration of various chlorinated hydrocarbons in samples of bed materials (in micrograms per kilogram) were: chlordane, from 0 to 14; DDT, from 0 to 19; and PCB's, from 0 to 11. Concentrations of aldrin, DDD, DDE, heptachlor, and heptachlor epoxide of 5.1 micrograms per kilogram or less were also detected. The presence of these compounds makes them potentially available for accumulation in the biological food chain.