EXPLORING THE LINKAGES BETWEEN RIVER WATER CHEMISTRY AND WATERSHED CHARACTERISTICS IN THE CLEAR FORK RIVER, OH

Non-point source pollution is currently the primary threat to riverine water quality in both urban and agricultural settings. Nevertheless, our ability to make better predictions on the fate of urbanized/agriculturally impacted aquatic ecosystems is greatly hindered by our lack of understanding of the relationship between land use change, hydrology and water quality. Here we present water chemistry data from the Clear Fork River, which drains a mixed urban-agricultural watershed in north-central Ohio. The watershed has experienced an increase in urbanization associated with a decrease in farmland. Between 1982 and 1997, urban land increased 22%, while 16% of farmland was lost. At the center of the watershed is the Clear Fork reservoir, which provides 60% of the drinking water to Mansfield, the largest urban center in Richland County with about 50,000 inhabitants. Stream water samples were collected monthly (between March and November) in eight stations along the river. Stations located within agricultural land presented DIN concentrations 2-3 times higher than those located within urban landscapes. N:P ratios indicate that most of the stations are nitrogen limited. Peak nitrate concentrations were observed in June for all stations and are positively correlated to the intensity of rainfall events. Similarly, the lowest values occurred in August following a dry spell that lasted a couple of weeks. There is also a strong positive correlation between soil OM content and stream water DIN concentration.