Nonpoint Source Pollution from Agricultural Runoff

An operational procedure has been developed which is suitable for estimating nonpoint source water pollution due to runoff from agricultural land and is sensitive to regional variations in weather, soils, and crop management. Although not presently applicable to snowmelt runoff, the procedure could be extended to winter runoff by use of suitable snowmelt estimating methods. Nitrogen and phosphorus in agricultural runoff were estimated for a five-watershed area totaling 578 sq km in Broome and Tioga Counties, N.Y., for the years 1971 and 1972. Comparison was made with two other estimates which were obtained using areal loading factors (losses of nutrients per unit area). Although the three different estimates were of comparable orders of magnitude, the loading factor estimates were not sensitive to the soils, weather, and crop distributions of the study region, and may overestimate losses of nitrogen in agricultural runoff.