Sustainable Water Management - Sustainable Practices in Geoenvironmental Engineering - page 82

FIGURE 3.4
(See color insert.) Iron runoff from a coal mine into canal area.
Natural sources of contaminants can also contribute to the contamination of ground-
water. Salt water intrusion from coastal aquifers can also degrade groundwater quality
by transporting salt into the groundwater (Melloul and Goldenberg, 1997). The arsenic
contaminated aquifers in West Bengal and Bangladesh discussed previously in Section
2.2.4 in Chapter 2 provide good examples of a combined “man-and-nature” impact on
the geoenvironment. Since these aquifers provide potable water for the majority of the
population of Bangladesh and some signiicant proportion of population in West Bengal,
it has been estimated that from 35 to 50 million people are at risk of arsenic poisoning.
Often referred to as the singular most dramatic case of mass poisoning of the human
race, the arsenic polluted aquifers serving the tube wells in the two countries contain
arsenic concentrations far in excess of the prescribed limits of the WHO. Worldwide, in
2007, it was estimated that more than 137 million people in over 70 countries including
the United States are affected by arsenic in drinking water (Smedley and Kinniburgh,
2002).
In the United States, a survey showed that more than 36% of the surface water does
not meet water quality objectives (U.S. Environmental Protection Agency [USEPA], 1996).
More recently, in the National Water Quality Inventory: Report to Congress for the 2004
Reporting Cycle (USEPA, 2009), U.S. states reported that of the assessed stream miles, lake
acres, and bay and estuarine square miles about 44%, 64%, and 30%, respectively, were
impacted suficiently that would not allow uses such as ishing and swimming. The most
common types of impairment of lakes shown in Figure 3.5 include pathogens, mercury,
nutrients, and organic enrichment/low dissolved oxygen from atmospheric deposition,
agriculture, hydrological modiications, and unknown or unspeciied sources. Increasing
population and economic growth are contributing to this problem. Major sources of con-
taminants are the agricultural industry and urban runoff from storm sewers. Although
problematic in some locations, the presence of pesticides and fertilizers is currently not a
huge concern. There is not a large amount of data concerning groundwater quality in the
United States.