Watershed Modeling of the Cannonsville Basin using SWAT2000. Version 1.0. Technical Report

This report describes the calibration and validation of a spatially distributed watershed model of the Cannonsville Reservoir Basin. The Soil and Water Assessment Tool 2000 (SWAT2000) was selected as the watershed model. A set of SWAT2000 inputs representative of the watershed conditions was derived from a wide array of data sources. Important methods were developed for converting available information to SWAT2000 inputs for groundwater soluble phosphorus concentrations, initial soil phosphorus levels and daily manure application.

The Cannonsville Reservoir is a New York City water supply reservoir located in upstate New York that has historically experienced water quality problems associated with phosphorus loading. As a result, the watershed has been subjected to multiple water quality regulations including a recent Total Maximum Daily Load (TMDL) assessment for phosphorus. The reservoir watershed covers an 1178 km2 area and is dominated by agriculture, particularly dairy farming. The SWAT2000 model of the Cannonsville Reservoir Watershed is a valuable tool that can be used to help identify and evaluate quantitatively the long-term effects of various phosphorus management options for mitigating loading to the reservoir.

SWAT2000 was developed by the Agricultural Research Service of the United States Department of Agriculture. SWAT2000 simulates through time the daily soil water balance, growth of plants, build-up and subsequent transport of soil nutrients to surface waters in response to agricultural management practices. The simulated mass balance of soil phosphorus in SWAT2000 is an important aspect of any watershed model that is to be used for regulatory purposes.