SEASONAL CHANGES IN STREAM WATER QUALITY ALONG AN AGRICULTURAL/URBAN LAND-USE GRADIENT.

We investigated downstream changes in dissolved oxygen (DO), pH, nitrate, total nitrogen (TNL total phosphorus (TP), Atrazine®. E. coli, and total suspended sediments (TSS) levels in two second-order watersheds with various amounts of riparian buffer coverage, and with more than 80% agriculture anti 3% residential land-use in the headwaters and 60-65% agriculture and 10% residential land-use lower in the watersheds. DO, pH, nitrate. TP, E, coli and TSS showed little variation in the downstream direction along this land-use gradient or as a function of riparian buffer coverage. However, a decrease in Atrazine and TN concentrations was associated with the increased percentage of land used for housing in the downstream direction from less than 3% to approximately 10% urban land-use. Benchmark analysis indicated overall poor water quality in both watersheds with respect to nitrate, E. coli. TN and TP. This study provides a baseline of water quality data for future studies assessing the impact of changing land-use and riparian zones on water quality at the watershed scale in till landscapes of the midwestern U.S., where rapid population growth leads to the conversion of agricultural lands into residential areas. [ABSTRACT FROM AUTHOR]