A comprehensive, distributed parameter, annual, watershed nonpoint source management
system (WATNPS) was developed for land management planning. WATNPS simulates annual
sediment, nitrogen (chemical and livestock organic), and phosphorus (chemical and livestock
organic) yields from nonpoint sources. The system is linked to a GIS platform to reduce the
input required by personnel during analysis. WATNPS predicts potential impacts of land
management practices on surface water quality.
Data were compiled for the Middle Fork Holston River (MFHR) drainage basin, Owl Run and Nomini Creek watersheds in Virginia. WATNPS utilizes annual screening models for the prediction of pollutant yields. Overland delivery ratio, phosphorus yield, and animal waste models were modified for use in the system. In-stream delivery ratio, and pollutant routing
procedures were developed as a part of the overall system functionality. Development and
calibration of individual in-stream delivery ratio parameters was performed based on single year
data from Nomini Creek and Owl Run.
A procedure was developed to rank individual watersheds and sites based on predicted
pollutant yields during screening. Simulation results and individual watershed characteristics
were used during the development of a drainage quality index (DQI). The DQI was developed
using statistical analysis to link a water quality indicator to predicted yields and watershed
characteristics. The DQI was developed to assess the impact of management within individual
watersheds and among watersheds within a drainage basin.
WATNPS was validated using observed data. During simulations WATNPS predicted
sediment yields within 50% of observed values. Nutrient yields were predicted within a order
of magnitude.
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