How much greater is the estimate of water available underground vs. water volume in freshwater lakes?  20 times greater.   50 times greater.   30 times greater.   10 times greater. 

One of the worst stories of groundwater pollution in the United States is centered on what source of groundwater contamination?  Mining operations.   Leaky underground storage tanks.   Deep injection wells.   Runoff from pesticides. 

What process of cleaning up groundwater contamination involves injecting air through deep wells to collect the volatiles from the contaminants?  Air sparging.   Deep injection.   Oxygen scrubbing.   Surface fanning. 

What type of aquifer lies between impermeable layers of rock and is not connected to the water in rivers and lakes?  Confined aquifer.   Shifting aquifer.   Open aquifer.   Unconfined aquifer. 

What percentage of all U.S. irrigated land is supplied with water from the Ogallala aquifer?  15%.   30%.   20%.   50%. 

How much of the Ogallala aquifer has been drained away under the Texas high plains?  About half.   About one fifth.   About two thirds.   About one third. 

Which area of the Ogallala aquifer has actually been increasing?  Sand Hill region of Nebraska.   Central region of Kansas.  There is no area of the aquifer that is increasing.   Southern region of Texas. 

What percentage of all available freshwater do humans expropriate from rivers, lakes and streams?  54%.   45%.   68%.   32%. 

How many large dams bisect waterways around the world?  85,000.   32,000.   40,000.   100,000. 

What fraction of the world's freshwater fish are threatened by habitat destruction and pollution?  One fourth.   One fifth.   One third.   One half.