NONPOINT-SOURCE POLLUTION POTENTIAL IN AN AGRICULTURAL WATERSHED IN NORTHWESTERN PENNSYLVANIA

A 155,947 ha portion of the Shenango River watershed in western Pennsy lvania was evaluated as to the potential impact of agriculture drainag e on water quality. Approximately a third of the area is being used as either cropland or pasture with approximately an equal percentage in forest lands. Eleven subwatersheds were evaluated as to their potentia l for nonpoint source pollution according to the criteria established by the Pennsylvania Department of Environmental Resources for the Ches apeake Bay Pollution Abatement Program. The individual components and overall rating for each subwatershed were then evaluated as to their c orrelation with four water quality variables based on 104 samples coll ected at 26 sampling stations throughout the watershed. There was a si gnificant correlation between the overall rating factor for each subwa tershed and each of the four water quality variables. In general, the watershed delivery factor, animal nutrient factor, and management fact ors were correlated with fecal coliform and phosphorus in the receivin g streams, whereas the ground water delivery factor appeared to be mor e important in determining nitrate concentrations in these streams. Th ese results indicate that manure and nutrient management, along with t he exclusion of livestock from streams and the enhancement and/or repl acement of riparian wetlands, are important approaches in reducing agr icultural impacts in fresh water ecosystems.