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

Digital tools such as Geographic Information Systems (GIS) store, anal yze, map, and illustrate large amounts of diverse electronic data. Thi s paper develops a GIS modeling user interface for delineating Wellhea d Protection Areas (WHPAs) around public water-supply wells. With this modeling interface, the user can extract the necessary information fr om the GIS database automatically. The CIS database can then store the delineated WHPAs for further analysis and display. The modeling inter face allows local agencies to delineate and manage WHPAs for hundreds of wells more efficiently and effectively than with the traditional pa per 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-s upply wells in the city were delineated using GIS and the modeling int erface. Detailed sensitivity analyses were completed to evaluate the e ffect of uncertainty in model parameters on the delineated WHPAs. Pote ntial sources of contamination within the delineated WHPAs were then i dentified using the GIS database. While GIS are perceived as an import ant tool that can enhance a user's ability for spatial data analyses, they have many problems. The system hardware and software require a su bstantial investment in financial and human resources. Database develo pment is a tricky process requiring planning and commitment; in most c ases, the anticipated outcome from GIS software development is not imm ediately realized.