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Environment Magazine September/October 2008

 

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Bytes of Note - Groundwater: A Tale of Two Settings

As with most natural resources, the use of groundwater carries with it very different sets of anxieties and outcomes from one part of the world—or, indeed, locality—to the next. In the United States, private household wells typically provide reliable, healthy drinking water with little need for outside help beyond the electricity to pump it. Along with this self- sufficiency, though, may come a low-level anxiety about water quality since no outside agency tests for contaminants; the responsibility to monitor the water in the well and protect the area around it falls squarely with the homeowner. Meanwhile, groundwater development in Bangladesh (and also in West Bengal, the nearby Indian state) has had unexpected and disastrous consequences. Intensive tube well development, first seen as the healthy alternative to biological surface contamination, yielded arsenic-rich water, creating a nationwide public health crisis that some call the biggest mass poisoning in the history of the world.

For most people who drink it, groundwater remains a bit of a mystery. Unlike rain, snow, glaciers, runoff, streams, lakes, oceans, and clouds, groundwater is the part of the water cycle that cannot be seen directly. (See http://ga.water.usgs.gov/edu/watercycle.html for a diagram of the water cycle available in 67 languages).

Much as water soaks into or drains out of a sponge, groundwater flows through underground aquifers, which are typically more or less horizontal units of unconsolidated sand, gravel, or cracked or porous rock bounded at least on the bottom by an impermeable layer of clay or rock. Water in aquifers closest to the surface ultimately seeps into streams or lakes. The top of these surface aquifers, called the water table, roughly parallels the surface of the topography above, sloping down toward the streams and lakes that the groundwater feeds. Wells can be drilled to near-surface or deeper aquifers to pump water to the surface for our use. For a brief explanation of groundwater’s formal vocabulary, see http://www.geology.arkansas.gov/water/groundwater.htm. This site also notes that, despite popular myth, it is extremely rare for water to create actual underground rivers or lakes. Environment Canada publishes an introduction to groundwater for the general public (Groundwater—Nature’s Hidden Treasure).

As they can with lakes, rivers, and streams, people can contaminate groundwater with pollutants that make it hazardous to drink. However, groundwater contamination is more complex because the pollutants can interact in various ways, such as binding with the sediment or rock particles in the aquifer. Cleanup can be difficult because of this and also because underground contaminants are hard to access. Unfortunately, aquifers in a number of areas around the world contain naturally occurring toxins that can be just as hazardous as anthropogenic pollutants.

Bangladesh’s problem with arsenic in groundwater began when international development agencies, including UNICEF and the World Bank, attempted to solve an earlier public health crisis. Bacterial pathogens in unfiltered surface water were (and still are) killing many people. Several Web sites report the unsourced estimate that around 250,000 children died each year. (This site provides a good introduction to the current cholera dilemma.) To provide what was thought to be a safe alternative, the development agencies began a huge campaign in the 1970s to sink wells across the country. Unfortunately, no one tested for the naturally occurring arsenic that leaches into the groundwater in a large part of Bangladesh. The arsenic-rich groundwater led to mass chronic arsenic poisoning that went largely unrecognized until the 1990s and remains a problem to this day. Thirty-five to seventy-seven million people may be exposed to contaminated water there. According to the World Health Organization, chronic arsenic toxicity results in a thickening and changing of skin color called hyperkeratosis and can lead to cancers of the skin, lungs, bladder, or kidneys.

There are nearly 10 million tube wells in Bangladesh. By 2007, more than half had been tested; 43 percent of those had unsafe levels of arsenic. One-third of the people surveyed were not using safe water sources, such as arsenic-free tube wells, filtered surface water, or rainwater tanks. For Bangladeshis still without safe water, there is some hope. In 2007, the U.S. National Academy of Engineering awarded large prizes to the top three competitors who developed promising low-cost, nonelectric, sustainable treatments that effectively remove arsenic at the point of use. The creator of the first-prize filter reported that 30,000 units had been deployed by 2007.

For those wishing to monitor the arsenic problem, the popular Arsenic Crisis Information Centre would seem to be a good source, but it appears to have gone dormant circa 2003. A Google search using a specific recent year (such as <arsenic Bangladesh 2007>) does, however, yield a number of the most recent ongoing efforts to assess and solve the problem. Natural arsenic in groundwater does occur in other parts of the world. While arsenic contamination in the United States sometimes makes the news, an arsenic map shows that unsafe concentrations tend to be restricted to very small portions of the country.

The fact that groundwater in the United States tends to be a very safe source of drinking water is likely of great comfort to the residents of homes not connected to a public water supply. Homes using groundwater account for 98 percent of the volume of water consumed by all self-supplied households (Estimated Use of Water in the United States in 2000, “Domestic” section). It is especially important for homeowners outside a water utility system to learn about groundwater because no agency monitors water quality for private wells.

The U.S. Environmental Protection Agency (EPA) booklet Drinking Water from Household Wells is a good place to start learning practical steps. Since local geology, hydrology, land use, and other activities all contribute to groundwater quality, the booklet recommends talking to local experts as one strategy for identifying local problems. It also describes potential problems that can come from land uses and activities, including farms, businesses, landfills, dumps, and household septic systems. It lists tastes, smells, and visible signs that indicate particular problems—with the caveat that many serious groundwater problems can only be found through testing. The publication suggests that water be tested “every year for total coliform bacteria, nitrates, total dissolved solids, and pH levels” and for additional chemicals if there is reason to suspect other problems. Another EPA source suggests that more frequent testing may be necessary if a well has been worked on; there has been a fuel or chemical spill near a well; or a household member is pregnant, nursing, or ill from an unknown cause. Homeowners may find labs to test their water using state links at http://www.epa.gov/safewater/labs.

In addition to the need for testing water and keeping abreast of community-wide threats such as those outlined in the publications above, homeowners who depend on groundwater should  be careful with household chemicals and should properly manage their septic systems. Because of the local nature and lack of standardized regulation of groundwater resources, choosing among groundwater Web sites can be challenging. Many state or local agencies or organizations produce good sites, a number of which have more widely applicable information than may be apparent from their local authorship; these should not be ignored. If specific local information is desired, however, state health departments typically maintain lists of county and local health departments, which may be of some assistance with household sanitation and water quality. Local agricultural extension agents  may also be of some help to homeowners.

Groundwater quality is not the only sustainability issue related to groundwater use. When people in communities or regions pump groundwater faster than it is naturally recharged, they deplete the aquifer, denying themselves or others of future water use. Such depletion occurs in many areas of the United States  and around the world (see Figure 2.3.2). Another concern is subsidence. In some areas, withdrawal of water actually changes the structure of the aquifer, allowing compression, sinking of land, and a decrease in the ability of the aquifer to hold water in the future. A final problem to mention is saltwater intrusion, where a coastal freshwater aquifer becomes saltier as fresh water is pumped out and salt water replaces it.

For those interested in a career in groundwater management, the National Ground Water Association (NGWA)  maintains a listing of potential mentors for students from the high school to graduate level. Of course, groundwater issues are worldwide, not just in Bangladesh and the United States. Recognizing this, NGWA also maintains a list of groundwater professionals willing to serve as workers or consultants on a volunteer basis for “nongovernmental,  private voluntary, faith-based, and other organizations in developing countries."

GEORGE E. CLARK is the environmental resources librarian at the Harvard College Library. Material for Bytes of Note may be directed to him at george_clark@harvard.edu.

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