An integrated approach for water quality assessment of a Kansas watershed

An integrated modeling process was used to estimate the nutrient loadings of different sub-watersheds of the Cheney Reservoir watershed, Kansas, USA. The Agricultural Nonpoint Source Pollution (AGNPS)-ARC INFO interface was used to extract input parameters from various Geographic Information System (GIS) layers, including a landcover layer prepared from Landsat TM image, for the AGNPS model during selected storm events. The curve numbers (CNs) were adjusted depending on the antecedent moisture condition (AMC) of the sub-watershed before each storm. The storm energy intensity (EI) values were computed using a probability method from a rainfall-EI relationship for the location of the study area. Several sensitive parameters of the AGNPS model were then calibrated to match the model-estimated total nitrogen (total-N) and total phosphorous (total-P) with the measured data on a sub-watershed basis during various runoff events. This process was validated by running the calibrated AGNPS model on each sub-watershed of the Cheney Reservoir watershed. This integrated modeling process was found to be effective for smaller watersheds that had adequate rainfall data.