Humanity uses a little less than half the water available worldwide. Yet occurrences of shortages and droughts (干旱) are causing famine and distress in some areas, and industrial and agricultural by-products are polluting water supplies. Since the world's population is expected to double in the next 50 years, many experts think we are on the edge of a widespread water crisis.
But that doesn't have to be the outcome. Water shortages do not have to trouble the world-if we start valuing water more than we have in the past. Just as we began to appreciate petroleum more after the 1970s oil crises, today we must start looking at water from a fresh economic perspective. We can no longer afford to consider water a virtually free resource of which we can use as much as we like in any way we want.
Instead, for all uses except the domestic demand of the poor, governments should price water to reflect its actual value. This means charging a fee for the water itself as well as for the supply costs.
Governments should also protect this resource by providing water in more economically and environmentally sound ways. For example, often the cheapest way to provide irrigation(灌溉)water in the dry tropics is through small-scale projects, such as gathering rainfall in depressions(凹地) and pumping it to nearby cropland.
No matter what steps governments take to provide water more efficiently, they must change their institutional and legal approaches to water use. Rather than spread control among hundreds or even thousands of local, regional, and national agencies that watch various aspects of water use, countries should set up central authorities to coordinate water policy.
21. What is the real cause of the potential water crisis.
A)Only harf of the world's warter can be used.
B)The world population is increasing faster and faster.
C)Half of the world's water resources have been seriously polluted.
D)Humanity has not placed sufficient value on water resources.
[答案与分析]：D。 文中第二段第二句：Water shortages do not have to trouble the world if we start valuing water more than we have in the past.如果我们现在比过去更加珍惜水的话，水资源短缺应不会困扰世界。
22. As indicated in the passage, the water problem .
A)is already serious in certain parts of the world. B)Has been exaggerated by some experts in the field
C)Poses a challenge to the technology of building reservoirs
D)Is underestimated by government organizations at different levels
[答案与分析]：A。 通读全文不难看出水资源问题在世界某些地方已变得很严重。文中第一段第二句：Yet occurrences of shortages and droughts are causing famine and distress in some areas,and industrial and agricultural by-products are polluting water supplies.更是说明了这一点。
23. According to the author, the water price should .
A)be reduced to the minimum B)stimulate domestic demand
C)correspond to its real value D)take into account the occurrences of droughts
[答案与分析]：C 。文中第三段第一句：Instead,for all uses'except the domestic demand of the poor,governments should price water to reflect its actual value.对水资源的利用，包括国内穷人对水的需求，政府应提高水价，以反映其真正价值。
24. The author says that in some hot and dry areas it is advisable to .
A)build big lakes to store water B)construct big pumping stations
C)build small and cheap irrigation systems D)channel water from nearby rivers to cropland
[答案与分析]：C。 文中第四段：Governments should also protect this resource by providing water in more economically and environmentally sound ways.For example,often the cheapest way to provide irrigation water in the dry tropics is...政府应通过为水资源建立更经济，更环保的有效方式来保护水资源。例如，最廉价的方式是……
25. In order to raise the efficiency of the water supply, measures should be taken to .
A)guarantee full protection of the environment B)centralize the management of water resources
C)increase the sense of responsibility of agencies at all levels D)encourage local and regional of water resources
[答案与分析]：B 。文中最后一句:Rather than spread control among hundreds or even thousands of local,regional,and national agencies that watch various aspects of water use,countries should set up central authorities to coordinate water policy.与其将权力分散到地方政府，由国家的代理机构来监督水资源的利用情况，不如国家建立调整用水政策的权威机构。
