Water lies beneath almost every part of the Earth's surface—mountains, plains, and deserts—but underground water is not always easy to find, and, once found, it may not be readily accessible. Groundwater may lie close to the surface, as in a marsh, or it may occur many hundreds of feet below the surface, as in some dry areas of the nation's West. The amount of groundwat…
Groundwater is not in underground lakes, nor is it water flowing in underground rivers. It is simply water that fills pores or cracks in subsurface rocks. When rain falls or snow melts on a ground surface, water may run off into lower land areas or lakes and streams. What is left is absorbed into the soil where it can be used by vegetation, seeps into deeper layers of soil and rock, or evaporates …
Water is always in motion. Groundwater generally moves from recharge areas, where water enters the ground, to discharge areas, where it exits from the ground into a wetland, river, lake, or ocean. Transpiration by plants whose roots extend to a point near the water table is another form of discharge. The path of groundwater movement may be short and simple or incredibly complex, depending on the g…
As groundwater travels its course from recharge to discharge area, it undergoes chemical and physical changes as it mixes with other groundwater and reacts with the minerals in the sand or rocks through which it flows. These interactions can greatly affect water quality and its suitability or unsuitability for a particular use. Water is a natural solvent capable of dissolving other substances. Spr…
The nation's use of groundwater grew dramatically in the last several decades of the twentieth century. According to a report from the USGS (Estimated Use of Water in the United States in 2000), the United States withdrew about 34 billion gallons per day (gpd) in 1950, reached 84 billion gpd in 1980, and dropped off a bit over the next several years before reaching a new high of 84.5 billio…
Until the mid-twentieth century, people believed that soil provided a barrier or protective filter that neutralized the downward migration of contaminants from the land FIGURE 4.8 Sources of groundwater contamination SOURCE: "Figure 6-2. Sources of Ground Water Contamination," in 2000 National Water Quality Inventory, U.S. Environmental Protection Agency, August 2002 surface …
All pollutants do not cause the same rate of contamination for the same amount of pollutant. Groundwater is affected by many of the following factors: …
In the EPA's National Water Quality Inventory—1998 Report to Congress (the latest data available for information on specific contaminants in groundwater) thirty-one of the thirty-seven reporting states identified the types of contaminants they found in groundwater. The states said that nitrates, metals, volatile and semivolatile organic compounds, and pesticides were the pollutants f…
Cleaning up the nation's groundwater is expensive. The costs associated with alternative water supplies, water treatment, and contaminant source removal or remediation are in the millions per site. The Water Protection Council in 1996 estimated $14 billion annually is needed to remediate groundwater and soil at Superfund sites, hazardous waste sites with corrective actions, leaking UST site…
Prevention of groundwater contamination is largely the responsibility of state and local government. In 1991 the EPA established a national groundwater protection strategy to place greater emphasis on comprehensive state management of groundwater resources. The EPA recognized that the wide range of land-use practices that can adversely affect groundwater quality is most effectively managed at the …
The nation's groundwater management is highly fragmented, with responsibilities spread over many federal, state, and local programs. Unique legal authorities at each government level allow for controlling one or more of the groundwater threats discussed here. For groundwater management to be successful in protecting and conserving this resource, these various authorities need to complement …
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