Research Article AnnGIS: Integration of GIS and a Continuous Simulation Model for Non-Point Source Pollution Assessment Puneet Srivastava Rick L Day Patrick Center for Environmental Department of Agronomy Research The Pennsylvania State University The Academy of Natural Sciences of Philadelphia Paul D Robillard and James M Hamlett Department of Agricultural and Biological Engineering The Pennsylvania State University Abstract Non-Point Source (NPS) models and monitoring data are often used to evaluate management practices and develop NPS pollution control plans. Application of a dynamic NPS model requires efficient input data acquisition, storage, organiz- ation, reduction, and analysis accompanied by manipulation, interpretation, reporting, and display of model outputs. A Geographic Information System (GIS) helps extract, store, and organize input data as well as manipulate and display model outputs. This paper illustrates the development of an integrated GIS system for a continuous simulation, pollutant-loading model, AnnAGNPS (Annualized AGricultural Non-Point Source Pollution). The integrated system, called AnnGIS, was developed using the ArcView Õ GIS and related program extensions. Using AnnGIS, modeling studies and management plans can be efficiently and easily developed. AnnGIS helps store, organize, and manipulate spatial and tabular data, extract spatial input parameters, develop analysis scenarios, and visualize input and output data in spatial, tabular, and graphical forms. AnnGIS is generic in nature (not limited to a particular geographic location) and can be successfully used in regions for which AnnAGNPS is designed. AnnGIS's powerful graphical user interface and reference data sets facilitate efficient and informed decision- making concerning agricultural non-point pollution control and management. Transactions in GIS, 2001, 5(3): 221±234 ß 2001 Blackwell Publishers, 108 Cowley Road, Oxford OX4 1JF, UK and 350 Main Street, Malden, MA 02148, USA. Address for correspondence: Puneet Srivastava, Patrick Center for Environmental Research, The Academy of Natural Sciences of Philadelphia, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103. E-mail: pxs159@hotmail.com