Wellhead protection area delineation using a coupled GIS and groundwater model

The 1986 Amendments to the United States Safe Drinking Wafer Act (SDWA) made wellhead protection an important issue for wafer suppliers in the US. These Amendments mandate that each Stale develop a wellhead protection program (WHPP) to protect the wellhead areas of all public water systems from contaminants that may have adverse human health effects. Data requirements to support a WHPP can become unwieldy without the benefit of a system that can handle large databases involving spatial relationships. Geographic information systems (GIS) store, analyse, map and illustrate data sets of complex spatial information, and can therefore be used to integrate and analyse various types of spatial data needed to delineate wellhead protection areas. The Cheyenne-Arapaho tribe has initiated a study of the groundwater resources on the Concho Reserve in Canadian County, Oklahoma, US. Groundwater within the Concho Researve is vulnerable to contamination because of the high permeability of the alluvial aquifer associated with the North Canadian River Pollutants of concern are associated with industrial agricultural and domestic sources in the recharge area. This paper describes the development of an interface allowing the Cheyenne-Arapaho tribe to delineate and manage wellhead protection areas (WHPAs). The system described herein provides for two modes of operation. The first, in which a well site is selected and possible sources of contamination are identified, is termed the forward problem. The second, where the ensemble area of possible well sites for which no known sources of contamination exist, is termed the backward problem. The system developed provides efficient management and protection of tribal drinking-wafer resources. (C) 1998 Academic Press.