ABSTRACT
Clean water is essential to human survival, and the earliest environmental regulations dealt with contamination of local water sources. Contamination of water resources has always occurred from a variety of anthropogenic activities, and, as population density increased, rivers, lakes and even oceans became contaminated. Direct discharge of industrial waste, domestic sewage, pesticide run-off from agricultural land, and acid rain all contributed to this contamina tion. Ground water may be polluted by landfill leachate, leaking storage tanks and pipelines, oil and gas wells, irrigation practices, waste disposal by direct underground injection, and other processes. Ground water and surface water can also contaminate each other, as they are not isolated.
