The use of water can be classified into four categories: (1) domestic use, (2) agricultural use, (3) in-stream use, and (4) industrial use.
Domestic Use of Water. Many rural residents still obtain safe water from untreated private wells, but urban residents are usually supplied with water from complex and costly water purification facilities. A relatively small amount of freshwater—roughly 8 percent of the global total—is withdrawn for domestic and municipal requirements. Domestic activities in highly developed nations require a great deal of water. This domestic use includes drinking, air conditioning, bathing, washing clothes, washing dishes, flushing toilets, watering lawns and gardens. Most of this domestic water is used as a solvent to carry away wastes, with only a small amount used for drinking. Yet all water that enters the house has been purified and treated to make it safe for consumption. Natural processes cannot cope with the highly concentrated wastes typical of a large urban area. The unsightly and smelly results present a potential health problem for the municipality.
The major problem associated with domestic use of water is maintaining an adequate, suitable supply for growing metropolitan areas. Demand for water in urban areas sometimes exceeds the immediate supply.
During the summer, water demand is high, and precipitation is often low. More domestic water is wasted than consumed. This loss, nearly 20 percent of the water withdrawn from public supplies (mainly through leaking water pipes and water mains), is amazingly large.
Agricultural Use of Water.The major consumptive use of water in most parts of the world is for agricultural purposes and principally for irrigation.
The amount of water used for irrigation and livestock continues to increase throughout the world. In some areas, irrigation is a problem because there is not a supply of water nearby. In some places, water must be piped hundreds of kilometers for irrigation.
Water loss from irrigation may be reduced in many ways. Increasing cost of water will stimulate conservation of water by farmers just as it does the owners. Another method is to reduce amount of water-demanding crops grown in dry areas, or change from high water-demanding to lower water-demand crops. Switching trickle irrigation also reduces water consumption.
In-Stream Use of Water.When the flow of water in streams is interrupted or altered, the value of the stream is changed. Major in-stream uses of water are for hydroelectric power, recreation, and navigation.
Sailing, waterskiing, swimming, fishing, and camping all require water of reasonably good quality. Overuse or inconsiderate use of water can degrade its quality. For example, waves generated by powerboats can accelerate shoreline erosion and cause siltation.
Most large urban areas rely on water to transport needed resources. During recent years, the inland waterway system has carried about 10 percent of the goods, such as grain, coal, ore, and oil.
Industrial Use of Water. Water for industrial use accounts for more than half of total water withdrawals. Ninety percent of the water used by industry is for cooling. Most industrial processes involve heat exchanges. Water is a very effective liquid for carrying heat away from these processes. If the water heated in an industrial process is dumped directly into a watercourse, it significantly changes the stream's water temperature. This affects the aquatic ecosystem by increasing the metabolism of the organisms and reducing the water's ability to hold dissolved oxygen.
Industry also uses water to dissipate and transport waste materials. In fact, many streams are now overused for this purpose, especially watercourses in urban centers. The use of watercourses for waste dispersal degrades the quality of the water and may reduce its usefulness for other purposes. This is especially true if the industrial wastes are toxic.
2. Answer the following comprehension questions:
1. What are the four categories of water use?
2. Where do rural and urban residents obtain safe water from?
3. How much water is withdrawn for domestic and municipal requirements?
4. How is water for domestic needs used?
5. What are the main causes of water loss?
6. Why do people have to reduce their water consumption?
7. What will future agricultural demand for water depend on?
8. Why is irrigation considered to be a problem in some areas?
9. What methods can be used to reduce the amount of water for irrigation?
10. What does in-stream use of water include?
11. What damage is caused to the nature by hydroelectric power plants?
12. How is water used for recreational purposes?
13. What is the effect of dredging on water quality?
14. For what purposes is water used in industry?
15. What measures are taken or can be taken in future to prevent water pollution?