URBAN EFFECTS ON WATER QUALITY IN A CORNBELT RIVER

Non-point source pollution is currently the primary threat to riverine water quality in industrialized and agricultural settings. To qualify and quantify non-point source input to surface water systems in multi-use landscapes, the ability to discern different sources of pollution is of extreme importance. This study investigates the geochemistry of the Upper Scioto River of central Ohio, whose watershed lies in the Eastern Cornbelt Plains and encompasses 1860 km² in the predominantly agricultural Wisconsin glacial till plains covering west-central Ohio. The Scioto River flows from agricultural land in its headwaters through Columbus, Ohio, the fifteenth most populous city in the United States. Using anion analyses, we show that that, with the exception of chloride, the geochemistry of the river is dominated by agricultural activities prior to its entry into the urban/suburban corridor. Long-term data collected in the 1960–1970’s indicate that chloride concentrations have increased in the agricultural portions of the river, but nitrate has not. Chloride appears to be an excellent indicator of human impact on surface water quality. Chloride increases significantly, by a factor of approximately 1.5, as the river flows through the metropolitan area of the watershed, but this increase is much less than seen in many European rivers. Nitrate yields (mass per unit area per unit time) in the urbanized areas are approximately twice those of the agricultural areas of the watershed.