Quiz: What You Don't Know About Water and Energy


Photograph by Sean Gallup, Getty Images

You know that nuclear plants need water to keep reactors cool, but how much do you really know about the connection between our power supply and our waterways?

About how much water is consumed each day by a 500-megawatt coal power plant?

  • 300 gallons ( 1,136 liters)
  • 3,000 gallons (11,356 liters)
  • 3 million gallons (11.3 million liters)
  • 300 million gallons (1.1 billion liters)

Water "consumed," or lost to evaporation, would be about 3 million gallons (11.3 million liters). Water withdrawn from rivers, lakes and other sources would be substantially more, 300 million gallons (1.1 billion liters) per day in plants with so-called "once-through" cooling systems. But most of that water is discharged back to its source, at a higher temperature, after it circulates through the plant cooling cycle.

In the United States, power plants are responsible for what percentage of the freshwater withdrawals from rivers, lakes, and other bodies of water?

  • 10
  • 20
  • 30
  • 40

Coal, nuclear, and other power plants that need cooling water for steam-driven turbine generators are responsible for about 40 percent of freshwater withdrawals, making thermoelectric generation the largest freshwater use in the United States. Agricultural irrigation is a close second, at 37 percent.

When a nuclear power plant has cooling towers instead of "once-through" cooling, it withdraws less water and protects aquatic life from high-temperature water discharges. But how much more water is lost to evaporation in a cooling tower system?

  • 10 percent
  • 25 percent
  • 50 percent
  • 80 percent

Nuclear power plants with cooling tower systems typically consume 720 gallons (2,725 liters) per megawatt-hour due to evaporation, compared to 400 gallons (1,514 liters) for once-through cooling, according to the U.S. Electric Power Research Institute.

Are there any power plants, other than wind and photovoltaic solar installations, that don't use water to generate electricity?

  • Yes
  • No

Some new designs of combined-cycle natural gas power plants use air-cooled condensers for their steam cycles, creating plants that use virtually no cooling water.

How much water is used per well to produce natural gas from shale through hydraulic fracturing?

  • 20 to 50 gallons (75 to 190 liters)
  • 200 to 500 gallons (757 to 1,893 liters)
  • 2 to 5 million gallons (7 to 19 million liters)
  • 20 to 50 million gallons (76 to 189 million liters)

The process that has unlocked vast quantities of natural gas from shale formations in the United States in the past decade, "fracking," involves injecting 2 million to 5 million gallons (7 to 19 million liters) of water at high pressure to create small fractures in the rock, causing the gas to be released.

How much water is consumed to produce and refine each gallon (3.79 liters) of gasoline (petrol)?

  • 1 gallon (3.79 liters)
  • 2.8 to 6.6 gallons (10.6 to 25 liters)
  • 20.6 to 60.6 gallons (78 to 229.4 liters)
  • 200.6 to 600.6 gallons (759.4 to 2273.5 liters)

Some 2.8 to 6.6 gallons (10.6 to 25 liters) are needed to produce each gallon of crude oil from conventional wells in Saudi Arabia or the United States and refine it into motor fuel. Water is produced from wells along with crude; recycling it can cut freshwater use. Unconventional production, accounting for an increasing share of global oil production, often requires more water.

How much water is consumed to produce one gallon (3.79 liters) of corn ethanol, based on production in Nebraska?

  • 1 gallon (3.79 liters)
  • 7 gallons (26.4 liters)
  • 70 gallons (265 liters)
  • 780 gallons (2,593 liters)

About 780 gallons, according to a U.S. National Research Council report, derived from recent figures showing irrigation for Nebraska corn at 2,100 gallons (7,949 liters) of water per bushel and each bushel yielding 2.7 gallons (10.2 liters) of ethanol.

Where did the world’s first hydroelectric power plant begin operation in 1882?

  • Fox River, Wisconsin, United States
  • Glomma River, Norway
  • Dal River, Iceland
  • Niagara River, between the U.S. and Canada

Paper manufacturer H.J. Rogers spearheaded construction of the world’s first hydroelectric power plant, which began operation on the Fox River in Appleton, Wisconsin, in 1882. It generated enough electricity to power his house, the plant itself, and a nearby building.

Which European country gets the greatest share of its electricity from hydropower?

  • Norway
  • Iceland
  • Albania
  • France

Norway gets 99 percent of its electricity from hydropower, and Albania is close behind at 98 percent. Iceland gets 75 percent of its power from hydro; in France, the share is 10 percent.

Electricity accounts for how much of the cost of municipal water processing and distribution?

  • 10 percent
  • 25 percent
  • 50 percent
  • 75 percent

Electricity is used for water pumping, conveyance, treatment, and distribution, making it the largest single cost of public water systems.





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