Modeling agricultural best management practices in the South Nation watershed

Abstract

The South Nation watershed consists of an area of roughly 3900 km2 in Eastern Ontario which drains into the South Nation River. The South Nation River in turn drains into the Ottawa River at the watershed outlet. The work presented here included the use of the continuous-simulation Annualized Agricultural Non Point Source (AnnAGNPS) 5.0 dynamic pollutant loading model, which was developed by the U.S. Department of Agriculture (USDA). In-stream water chemistry was also an important element of a meaningful analysis. The dynamic water-quality model CE-QUAL-RIV1 was selected due to its riverine nature, which is closely linked with the AnnAGNPS concept of a channel network. Utilities were developed to enhance the input and output capabilities of both codes. The linked models were then calibrated to the available data, and a case matrix focused on predicting feasibility of best management practices (BMPs) within the context of climate change was constructed and simulated. The calibration process was done manually at first, based on the results of a sensitivity analysis conducted on the AnnAGNPS package as part of the work. Subsequently, the use of an automatic genetic-algorithm based approach (also developed as part of this work) was explored, which yielded an improvement in the calibrated model and was therefore used as a base case of the model. The case matrix examined 4 individual BMPs, along with 4 combined BMP scenarios. (Abstract shortened by UMI.)