GEOGRAPHIC INFORMATION-SYSTEM BASED NONPOINT POLLUTION MODELING

The reauthorization of the Clean Water Act reemphasizes the need for r egional scale monitoring and management of nonpoint pollution loads. T he magnitude of the task will require that local governments and their consultants integrate information systems and modeling if they are to manage the massive data sets and conduct the array of simulations tha t will be needed to support the decision making processes. Interfacing geographic information systems (GIS) and nonpoint pollution modeling is a logical approach. The objective of the present study was to use t he 37,000-acre area defined by the Kensington Quadrangle sheet in Mont gomery County, Maryland, to show that GIS-supported nonpoint pollution modeling is practical and economically attractive. The purpose of the GIS is to estimate the spatial distribution of nonpoint nitrogen, pho sphorous, zinc, lead, BOD, and sediment using a model developed by the Northern Virginia Planning District Commission. The system allows the user to change land. uses in subareas to simulate the consequences of additional development or alternate management strategies. The tests show that in-house development of this type of special purpose GIS is a practical alternative to vendor supplied systems and that the requir ed databases can be developed quite reasonably.