Nonpoint-source pollution (NPSP) poses a special challenge to society's ability to manage its collective environmental good - especially surface and groundwater quality. Since there is no `point', such as an outfall pipe, from which the pollution is being discharged and can be measured, pollution can reach the ambient environment without being monitored. Since management of air and water polution requires the definition and enforcement of limits on discharges or the imposition of fees on those discharges, inability to measure limits our ability to manage this environmental problem. This book presents a state-of-the-art review and discussion of economists' efforts to resolve this major problem and attempts to provide a way of working around it. The book sets forth the theoretical issues, modeling, and the actual programs set up to confront this issue.

In 1997, New York City adopted a mammoth watershed agreement to protect its drinking water and avoid filtration of its large upstate surface water supply. Shortly thereafter, the NRC began an analysis of the agreement's scientific validity. The resulting book finds New York City's watershed agreement to be a good template for proactive watershed management that, if properly implemented, will maintain high water quality. However, it cautions that the agreement is not a guarantee of permanent filtration avoidance because of changing regulations, uncertainties regarding pollution sources, advances in treatment technologies, and natural variations in watershed conditions. The book recommends that New York City place its highest priority on pathogenic microorganisms in the watershed and direct its resources toward improving methods for detecting pathogens, understanding pathogen transport and fate, and demonstrating that best management practices will remove pathogens. Other recommendations, which are broadly applicable to surface water supplies across the country, target buffer zones, stormwater management, water quality monitoring, and effluent trading.

In April 1992 the Foundation Eni Enrico Mattei organized a workshop on the regulation of nonpoint source pollution. This volume inc1udes the proceedings of that meeting, as well as additional original contributions, in an attempt to provide an overview of recent theoretical developments in the field. Research on the causes, consequences, and control of nonpoint source pol lution has been carried out over the last two decades. Interest in this subject has grown as a result of the increasing recognition of the insufficiency of traditional pollution control policies focused on the large scale, confined, and general ly predictable pollutant discharges. In fact, many contemporary problems are caused by the combined activities of small polluters, along with natural pro cesses, intermittent and unpredictable events, and often involve pollutants with complex environmental outcomes. Despite the progress made in understanding the nature and size of pollution from diffuse sources, the issue of regulation is still far from being system at ically and adequately addressed. This policy vacuum is partly attributable to the difficulty of adapting the traditional point source regulatory tool kit to the specific features of nonpoint source problems. Such features inc1ude the tech nical difficulty of identifying sources and measuring individual emissions, their variability over time and space, the role played by natural processes in detennin ing pollutant discharges at source and their ultimate impacts on the receiving environmental media.