CONTAMINANT HYDROGEOLOGY: REJUVENATE THE RESEARCH AGENDA

Previous research has suggested that because most groundwater used for public supply is much older than sources of anthropogenic contamination, ultimate impacts of this contamination may not appear in water supply wells for several decades or centuries. Limited monitoring data and models indeed suggest such trends, and groundwater overdraft is setting the stage for gradual salinization of groundwater in some irrigated basins. The unknown, future groundwater quality in regional systems should therefore be a top research priority of the hydrologic community. While most contaminant hydrogeology research has focused almost exclusively on plume-scale processes, long-term groundwater quality sustainability questions demand a complementary genre of research that is more regional in scope (~10^2 km) and covers longer time scales (~10^1 – 10^2 yr). An objective of the research would be to both estimate present groundwater quality in basins and to model long-term change in quality centuries into the future. The necessary monitoring data are lacking in most basins, and even where the monitoring data are good, they do not span the decades-to-centuries time scales that are commensurate with the transport and fate processes. Hence, the need for intensive monitoring will never diminish. Further, modeling research must be directed toward simulating the upscaled physical, chemical and biological phenomena necessary for predicting long-term groundwater quality change, just as climate modeling has developed in response to the need to better understand effects of greenhouse gases. Scientific and social parallels between the groundwater quality sustainability problem and global climate change research will be discussed.