Evaluating the effects of agricultural practices on water quality by interfacing GIS with computer models

Nonpoint source pollution from agricultural activities significantly impacts quality of receiving water bodies, including increases in stream sediments and nutrients, and occurrence of pesticides in both surface and ground water. Agricultural activities in the West Wellfield Interim Protection Area (WWIPA), located in West Dade County in South Florida, have potential to impact both the environmentally sensitive Everglades and Florida Bay, and the Biscayne aquifer. The Hydrological Simulation Program-Fortran (HSPF) has been used to simulate water and constituent transport in the WWIPA and to determine possible impacts. Surface runoff, groundwater recharge, and transport of sediments, nutrients and pesticides are simulated by this model. ARC/INFO Geographic Information Systems (GIS) is interfaced with HSPF to store, manage, and display data, and derive input parameters for the model. Results of HSPF simulations are also visually presented through GIS. A GIS user interface was developed for the study area. Menus were created through which the database can be queried to derive model parameters and to visually present results through maps. Model results show that sediments, nutrients and pesticides are present in surface runoff, and nutrients enter the ground water. Various model test runs were made to minimize pollution levels without hindering agricultural production. They include application of minimum required rates of fertilizers, replacement of fertilizers by sewage sludge, and the effect of future urbanization