Evaluation of Nutrient Component of AnnAGNPS Model in a Watershed in Ontario

Abstract

Abstract: The water impairment with nutrient losses from non-point source pollution (NPS) is a major concern in different watersheds in Ontario where agricultural and live stock production are the major activities. The Annualized Agricultural Non-Point Source (AnnAGNPS) model has been applied in a watershed situated in the Southern Ontario to investigate model simulated N (N) and P (P) output. The model was run from 1991 to 1995 and the transport of dissolved and attached part of both the nutrients with runoff and clay particles was investigated. Since very limited observed nutrient data was available in the studied watershed and thus it was difficult to obtain a reasonable comparison between the simulated and observed values. The study results show that the dissolved and attached N has followed the similar trend of transport with the runoff and clay particles respectively. The model underpredicetd the total N and overpredicted the total P. The R2 and correlation coefficient was 0.75 and 0.19 for N and 0.82 and 0.23 for P respectively. The uncertainty of the input parameters and excessive use of manure were assumed to be the main reason behind the discrepancy. However, it was also obvious from the study that the model performance may be improved with proper calibration and further investigation on the fate and transport of the nutrient components.