GIS Interface for GWLF Watershed Model

In the last ten years, there has been a growing understanding of the importance of looking at water resource issues from a watershed perspective. Storm water, stream flow, groundwater, and aquatic resources are linked by the hydrologic cycle. Analysis of water resources problems invariably leads to interactions among these elements. Typical goals for watershed management are to reduce flooding, improve water quality, or restore lost habitat. It is not unusual for projects to serve multiple goals, nor is it unusual for the goals to change as stakeholders become more involved. Two methods of determining watershed condition are monitoring and modeling. Monitoring can provide good information on the current state of the watershed. However, when it is necessary to estimate changes resulting from future conditions, or to test alternative improvement scenarios, a watershed model is the primary tool. There are a large number of hydrologic and water quality models which have been developed or adapted for use in analyzing watershed processes. A comprehensive survey of computer models for analyzing water quality was published by the Environmental Protection Agency (EPA) in the Compendium of Tools for Watershed Assessment and TMDL Development, (Shoemaker et al, 1997) which described three levels of models: Simple, Mid-Range, and Detailed. They can be categorized by the amount of input data needed, the degree of effort and expertise needed, the need for calibration, and the accuracy of the results.