Author(s)

D. Cluis, G. Chardonneau, G. Gangbazo & S. Proulx

Abstract

Physically-based simulation models are powerful tools to assess the origin and fate of non-point sources of contaminants generated by agricultural activities. They allow to locate vulnerable areas and questionable practices contributing to the impairment of the surface waters in rural areas. AnnAGNPS is a new continuous model being developed at the National Sedimentation Laboratory (USDA-ARS); it is the direct successor of the event-based AGNPS model. AnnAGNPS simulates, at the watershed scale, the load in N, P and SS exported by the surface waters in response to weather, physical characteristics of the watershed, and agricultural practices such as crop types, fertilisation rates and scheduling, manure spreading, and other field operations. The model has been applied to a small intensively cultivated Quebec watershed that is also supporting intensive livestock breeding (dairy cows and hogs). This well-documented experimental watershed was continuously monitored for meteorology, river discharge and water quality parameters, even during the winter. Using the data of 1998 and 1999, simulated export values were compared with measurements showing a good agreement in the general pattern of the exported loading spells which are triggered by the field operations and by precipitation events. During the winter and during the spring snow melt, sizeable discrepancies appeared both for the simulated discharges and for the mass loading.

Keywords