Most of Earth’s freshwater sits underground. Worldwide, about 70 percent of the groundwater drawn to the surface goes for farming. But surface waters — rivers and streams — come from groundwater, too. Drawing too much groundwater over a short time can be harmful. Natural waterways can begin to empty. And that can hurt freshwater ecosystems. Scientists consider this a tipping point when small actions can begin making unusually big differences.
A new study has found that 15 to 21 percent of tapped water (自来水) areas have reached this sort of tipping point. Most of those tapped rivers and streams are in dry areas. Farmers in these areas use groundwater to water their crops. At present drawing rates, the study predicts that 42 to 79 percent of water areas around the world where groundwater is drawn up for use at the surface will reach tipping points by 2050.
A healthy groundwater aquifer (含水层) protects ecosystems against seasonal ups and downs in the use of water. That provides stability for area plants and animals. But if too much groundwater is drawn up from below, surface waters will begin to flow into the aquifer, which can harm what are living in rivers and streams.
De Graaf and the study team set up a computer model. It linked groundwater drawing and water flows within rivers. The model covered fifty years, from 1960 to 2010. Then the researchers used climate forecasts to help the model predict what might happen in future years. Throughout, they kept groundwater drawing rates sustainable. More than half of drawn water areas are likely to cross this ecological tipping point before 2050, the model finds.
“We need to be thinking about this now, not in 10 years,” De Graaf says. “Our study shows us where to target more sustainable efforts.”
8. What does the “tipping point” in paragraph 1 mean?
A. End point. B. Breaking point.
C. Freezing point. D. Boiling point.
9. What is the writer’s purpose of writing the text?
A. Warn us that the surface water can pollute the groundwater.
B. Warn us of watering the crop by groundwater.
C. Tell us the relation of groundwater and surface water.
D. Warn us that the overuse of groundwater can destroy the ecosystem.
10. What is the part the groundwater plays in the environment?
A. Keeping the stability of natural water.
B. Protecting ecosystems from pollution.
C. Clearing surface waters to be drinkable.
D. Providing stability for the local economy.
11. How did the researchers conduct the study?
A. They predicted the result based on the old data.
B. They happened to work out the result.
C. They measured all the groundwater and surface water.
D. They did questionnaire surveys on the water information.
【答案】
A new study has found that 15 to 21 percent of tapped water (自来水) areas have reached this sort of tipping point. Most of those tapped rivers and streams are in dry areas. Farmers in these areas use groundwater to water their crops. At present drawing rates, the study predicts that 42 to 79 percent of water areas around the world where groundwater is drawn up for use at the surface will reach tipping points by 2050.
A healthy groundwater aquifer (含水层) protects ecosystems against seasonal ups and downs in the use of water. That provides stability for area plants and animals. But if too much groundwater is drawn up from below, surface waters will begin to flow into the aquifer, which can harm what are living in rivers and streams.
De Graaf and the study team set up a computer model. It linked groundwater drawing and water flows within rivers. The model covered fifty years, from 1960 to 2010. Then the researchers used climate forecasts to help the model predict what might happen in future years. Throughout, they kept groundwater drawing rates sustainable. More than half of drawn water areas are likely to cross this ecological tipping point before 2050, the model finds.
“We need to be thinking about this now, not in 10 years,” De Graaf says. “Our study shows us where to target more sustainable efforts.”
8. What does the “tipping point” in paragraph 1 mean?
A. End point. B. Breaking point.
C. Freezing point. D. Boiling point.
9. What is the writer’s purpose of writing the text?
A. Warn us that the surface water can pollute the groundwater.
B. Warn us of watering the crop by groundwater.
C. Tell us the relation of groundwater and surface water.
D. Warn us that the overuse of groundwater can destroy the ecosystem.
10. What is the part the groundwater plays in the environment?
A. Keeping the stability of natural water.
B. Protecting ecosystems from pollution.
C. Clearing surface waters to be drinkable.
D. Providing stability for the local economy.
11. How did the researchers conduct the study?
A. They predicted the result based on the old data.
B. They happened to work out the result.
C. They measured all the groundwater and surface water.
D. They did questionnaire surveys on the water information.
【答案】
苏19057182-3号