ABSTRACT
Groundwater is sometimes referred to as the hidden source of water supply because it resides in the subsurface. It is of vital importance in areas where dry summers and extended droughts cause surface supplies to disappear. More than 1.5 billion people worldwide and more than 50% of the population of the United States rely on groundwater for their primary source of drinking water (Alley et al. 2002). Threats to groundwater quality have risen in importance, given the increased dependence on groundwater supplies and the long times required for clearance of contamination.
