填空题

Humanity uses a little less than half the water available worldwide.
Yet occurrences of shortages and droughts are causing famine in some
but industrial and agricultural by-products are polluting water supplies. (1) _____
Since the world’s population is expecting to double in the next 50 years, (2) _____
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 started valuing water more than we (3) _____
have in the past. Just like we began to appreciate petroleum more after (4) _____
the 1970s oil crisis, today we must start looking at water from a fresh
economical perspective. We can no longer afford to consider water a (5) _____
virtual free resource of which we can use as much as we like. (6) _____
Instead, for all uses except the domestic demand of the poor,
governments should price water to reflect their actual value. This means (7) _____
charging a fee for the water itself as well as for the demand costs. (8) _____
Governments should also protect this resource by providing
water with more economically and environmentally sound ways. (9) _____
Often the cheapest way to provide irrigation water in the dry tropics
is through small-scaled projects, such as gathering rainfall in depressions (10) _____
and pumping it to nearby cropland.