AN INTERACTIVE MODELING ENVIRONMENT FOR NONPOINT-SOURCE POLLUTION-CONTROL

Non-point source pollution continues to be an important environmental and water quality management problem. For the most part, analysis of n on-point source pollution in watersheds has depended on the use of dis tributed models to identify potential problem areas and to assess the effectiveness of alternative management practices. To effectively use these models for watershed water quality management, users depend on i ntegrated geographic information systems (GIS)-based interfaces for in put/output data management. However, existing interfaces are ad-hoc an d the utility of GIS is limited to organization of input data and disp lay of output data. A highly interactive water quality modeling interf ace that utilizes the functional components and analytical capability of GIS is highly desirable. This paper describes the tight coupling of the Agricultural Non-point Source (AGNPS) water quality model and ARC /INFO GIS software to provide an interactive hybrid modeling environme nt for evaluation of non-point source pollution in a watershed. The mo deling environment is designed to generate AGNPS input parameters from user-specified GIS coverages, create AGNPS input data files, control AGNPS model simulations, and extract and organize AGNPS model output d ata for display. An example application involving the estimation of pe sticide loading in a southern Iowa agricultural watershed demonstrates the capability of the modeling environment. Compared with traditional methods of watershed water quality modeling using the AGNPS model or other ad-hoc interfaces between a distributed model and GIS, the inter active modeling environment system is efficient and significantly redu ces the task of watershed analysis using tightly coupled GIS databases and distributed models.