Coupling vadose zone models with GIS: Emerging trends and potential bottlenecks

The capabilities of geographic information systems (GIS) to capture, edit, manipulate, analyze, and display spatial and nonspatial data have long been recognized. Since its initial development in the 1960s, GIS technology has been used extensively to generate and spatially organize large volumes of data to support modeling of contaminant transport in the vadose zone. In the literature, however, two constantly recurring themes have been, on one hand, the opportunities that GIS provide for sophisticated analysis and visualization of spatial data, and on the other hand, their inadequacy for research and application in many disciplines, including environmental modeling. In vadose zone modeling, the gap between user demands and the functional capabilities of GIS have become something of a cliche. An intensive research effort will be needed to couple vadose zone models with GIS. The extent to which such research is advantageous depends upon the benefits to be derived and the potential problems that can be encountered. This paper examines broad issues concerning the coupling of vadose zone models with GIS and emphasizes the emerging trends and potential bottlenecks. Application examples involving the coupling of some vadose zone models of nonpoint source pollution with GIS are described. The issues addressed will help to explain how to loosely, closely, or tightly couple models with GIS, and to hopefully stimulate more discussions and future research activities.