Simulating Atrazine Transport with HSPF in an Agricultural Watershed

Surface water pollution in rural areas is related to agricultural practices. Field applications of pesticide can contribute to water degradation. The model HSPF includes a module for simulating the degradation and transport of pesticides. This model was tested using data from a 78 ha watershed in the province of Québec, Canada. Model parameters related to hydrologic and pesticide transport processes were calibrated. The study period extended from June 1991 to November 1993. For the calibration period, correlations between observed and simulated streamflows were 0.73, 0.87, and 0.90 for daily, weekly, and monthly intervals, respectively; whereas for the verification period, values of 0.67, 0.91, and 0.93 were obtained. Pesticide concentrations were measured at the outlet of the watershed from February to November 1993. This short period of time allowed calibration of the pesticide component but precluded verification. Variations of atrazine concentration were well simulated by Hydrological Simulation Program FORTRAN (HSPF), with simulated concentrations in the same range as observed values, and with peak concentrations occurring at the same time.