A primer on nonpoint pollution

IDEAS about water pollution and pollution control once were simple and non-controversial. Water perceived to be cloudier, greener, smellier, or more littered was labeled polluted, and the major water user was blamed for ruining the old mill stream or pond. As water quality problems became more widespread, public concern increased. This concern spawned vigorous efforts by scientists and engineers to better understand and control fluctuations in water quality. Now it is known that waterbodies, like other environmental systems, are complex, and that changes in water quality can be natural, artificial, reversible, or even undetectable to unaided human senses. And while pollution from localized, obvious sources (point sources) may be easy to identify and control, resulting improvements in water quality may be disappointing. Consequently, attention has shifted in recent years to the more diffuse (nonpoint) sources of pollution, which are more difficult to control, and to those ubiquitous pollutants that originate from point sources but disperse before entering waterbodies. Nonpoint sources are responsible for at least half of all water pollution. They are the major contributors of such materials as sediments, nutrients, pathogenic bacteria, pesticides, acid rain, and polychlorinated biphenyls (PCBs). Research was initiated on the causes, consequences, and control …