A GEOGRAPHIC INFORMATION-SYSTEM (GIS) USER INTERFACE FOR DELINEATING WELLHEAD PROTECTION AREAS

Digital tools such as Geographic Information Systems (GIS) store, analyze, map, and illustrate large amounts of diverse electronic data. This paper develops a GIS modeling user interface for delineating Wellhead Protection Areas (WHPAs) around public water-supply wells. With this modeling interface, the user can extract the necessary information from the GIS database automatically. The CIS database can then store the delineated WHPAs for further analysis and display. The modeling interface allows local agencies to delineate and manage WHPAs for hundreds of wells more efficiently and effectively than with the traditional paper maps and overlay system. In order to demonstrate the efficiency of the user interface, this paper presents a wellhead delineation pilot study for the City of Houston. WHPAs for the 202 active public water-supply wells in the city were delineated using GIS and the modeling interface. Detailed sensitivity analyses were completed to evaluate the effect of uncertainty in model parameters on the delineated WHPAs. Potential sources of contamination within the delineated WHPAs were then identified using the GIS database. While GIS are perceived as an important tool that can enhance a user's ability for spatial data analyses, they have many problems. The system hardware and software require a substantial investment in financial and human resources. Database development is a tricky process requiring planning and commitment; in most cases, the anticipated outcome from GIS software development is not immediately realized.