Water Resource Problems

Too Little Water. A number of experts consider the availability of adequate supplies of fresh water to be the most serious long-range problem confronting the world and the United States. At least 80 arid and semiarid countries, accounting for nearly 40% of the world's population, now experience serious periodic droughts and have considerable difficulty growing enough food to sup­port their populations. Most of these countries are in Asia and Africa. During the 1970s, major drought dis­asters affected an average of 24.4 million people and killed over 23,000 a year—a trend continuing in the 1980s. By 1985 more than 154 million people in 21 tropical and subtropical countries in Africa were on the brink of starvation because of the combined effects of rapid population growth, prolonged drought, land misuse, war, and ineffective government policies for water and soil resource management and agricultural development.

In many LDCs, poor people must spend a good part of their waking hours fetching water, often from polluted streams and rivers. To get water, many women and children in LDCs walk 16 to 25 kilometers (10 to 15 miles) a day, carrying heavy water-filled jars on their return trip.

Although reduced average annual precipitation usually triggers a drought, rapid population growth and poor land use intensify its effects. In many LDCs, large numbers of poor people have no choice but to try to survive on drought-prone land by cutting trees, growing crops at higher, more erosion-prone eleva­tions, cultivating poor soils, and allowing their live­stock to overgraze grasslands. The resulting land deg­radation contributes to the severity of long-term drought by reducing the amount of rainfall absorbed and slowly released by vegetation and soils. In many cases, the result is desertification.

Too Much Water. Other countries get enough pre­cipitation on an annual basis but receive most of it at one time of the year. In India, for example, 90% per­cent of the annual precipitation falls between June and September—the monsoon season. This downpour runs off so rapidly that most of it cannot be captured and used. The massive runoff also leads to periodic flooding.

During the 1970s, major flood disasters affected 15.4 million people, killed an average of 4,700 people a year, and caused tens of billions of dollars in prop­erty damages—a trend that continued in the 1980s. Although floods are classified as natural disasters, human beings have contributed to the sharp rise in flood deaths and damages since the 1960s by remov­ing water-absorbing vegetation and soil through cul­tivation of marginal lands, deforestation, overgrazing, and mining. Urbanization also increases flooding, even with moderate rainfall, by replacing vegetation with highways, parking lots, shopping centers, office buildings, homes, and numerous other structures.

Death tolls and damages from flooding have also increased because many poor people in LDCs have little choice but to live on land subject to severe peri­odic flooding and because many people in LDCs believe that the benefits of living in flood-prone areas out­weigh the risks. Many urban areas and croplands in LDCs and MDCs are situated on floodplains—flat areas along rivers subject to periodic flooding—and coast-lands because these sites are level, have highly fertile topsoil deposited by rivers, are close to supplies of surface water and water transportation routes, and provide recreational opportunities.

Since 1925 the U.S. Army Corps of Engineers, the Soil Conservation Service, and the Bureau of Recla­mation have spent more than $8 billion on flood-con­trol projects such as straightening stream channels (channelization), dredging streams, and building dams, reservoirs, levees, and seawalls. Despite these efforts— and because these projects stimulate development on flood-prone land—property damage from floods in the United States has increased from about half a bil­lion dollars a year in the 1960s to an average of about $3 billion a year in the 1980s.

A number of effective methods exist for prevent­ing or reducing flood damage: replanting vegetation in disturbed areas to reduce runoff, building ponds in urban areas to retain rainwater and release it slowly to rivers, and diverting rainwater through storm sewers to holding tanks and ponds for use by industry. Floodplains should also be clearly identified, and laws or zoning regulations should be used to discourage their use for certain types of development. Sellers of property in these areas should be required to provide prospective buyers with information about average flood frequency.

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v.	n.	adj.	adv.	prep.

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OBVIOUSLY • ACTUALLY • YET • HENCE • THEREBY.

1. Symptoms such as pain, fever, and vomiting are not diseases. … they are defense mechanisms.

2. "Psychotic" means that a patient has lost touch with reality, …"neurotic" refers to a less serious state.

3. People have always recognized the waste, brutality, and inhumanity of war, … it goes on.

4. The mesosphere is important … that it contains only about 0.1 per cent of the total mass of the atmosphere.

5. As a rule, aquatic reptiles use the same means of propulsion as fish and whales, …they use powerful beats of the tail.

6. The heat increases, … the entropy increases.

7. Cells and antibodies may co-operate, … destroying invading bacteria.

8. For a person who weighs less, the concentration of alcohol will … be proportionally higher.

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Periodic, experts, population, tropical, combined, agricultural, vegetation, massive, percent, season, cultivation, center, transportation, recreational.

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