Applications of GIS to the Modeling of NonPoint Source in the Vadose Zone: A Conference Overview

Because of their ubiquitous nature and potential chronic health effects, nonpoint source (NPS) pollutants have become a focal point of attention by the general public, particularly regarding pollution of surface and subsurface drinking water sources. The NPS pollutants pose a technical problem because of the areal extent of their contamination that increases the complexity and sheer volume of data far beyond that of point-source pollutants. The spatial nature of the NPS pollution problem necessitates the use of a geographic information system (GIS) to manipulate, retrieve, and display the large volumes of spatial data. This overview provides a brief introduction and review of the modeling of NPS pollutants with GIS and a brief discussion of some of the papers presented at the ASA-CSSA-SSSA 1995 Bouyoucos Conference entitled Applications of GIS to the Modeling of Nonpoint Source Pollutants in the Vadose Zone. P OINT-SOURCE POLLUTANTS or rather pollutants that are associated with a point location such as a toxicwaste spill site have received the greatest attention in the past because of the obvious severity of their impact at a localized point. Even though point-source pollution is generally highly toxic, it is relatively easily controlled and identifiable. However, over recent years concern has shifted more to pollutants that are low in concentration, but ubiquitous in nature and referred to as NPS pollutants. The NPS pollutants are contaminants of surface and subsurface soil and water resources (e.g., sediment, fertilizers, pesticides, salts, and trace elements) that are diffuse in nature and cannot be traced to a point location. Often times, NPS pollutants are naturally occurring such as salts and trace elements in soils or are the consequence of direct application by humans (e.g., pesticides and fertilizers), but regardless of their source they are generally the direct consequence of human activities (e.g., agriculture, urban runoff, hydromodification, and resource extraction). The threat of NPS pollutants varies throughout the world. Yet, NPS pollutants are a problem of global importance (Duda, 1993). The reason is because NPS pollution problems do not recognize the boundaries between nations, nor are they necessarily isolated by the physical barriers between continents. As the worlds population continues to grow, the foreD.L. Corwin, soil scientist, USDA-ARS, U.S. Salinity Lab., 450 West Big Springs Road, Riverside, CA 92507-4617; R.J. Wagenet, professor and Dep. Head, Dep. of Soil, Crop and Atmos. Sciences, Emerson Hall, Cornell Univ., Ithaca, NY 14853. Received 24 Aug. 1995. *Corresponding