ABSTRACT
WEND-P is a watershed-scale modeling process that uses dynamic simulation technology integrated with mass balance concepts to evaluate the flow of P into, out of, and within a watershed. The utility of integrating dynamic simulation and mass balance was initially demonstrated in modeling studies of P dynamics resulting from best management practices (BMP) implementation at the field scale (Cassell and Clausen 1993) and in understanding P dynamics in reaches of flowing streams (Hoffmann et al. 1996). The first watershed-scale WEND-P model (WEND-P1) was developed by Alan Cassell of the University of Vermont and Robert Kort of the Natural Resources Conservation Service to evaluate long-term trends in P export from the Winooski River watershed to Lake Champlain in northern Vermont (Cassell et al. 1998b). WEND-P1 reflects the type of agriculture, forest management, industry, and other conditions that characterize the Winooski River watershed as a rapidly urbanizing watershed where dairy is the dominant form of agriculture and where food processing and electronics are the main industries. This first WEND-P model attempted to identify the major sources of P in the watershed and to determine how land use and policy changes could affect export of P from the watershed over time.
