University of Bristol
Institute of Physics logo
Why not try our other site: BEEP Biology & Ethics

Renewable energy

Water power: Falling water

Dams and greenhouse gases

While water power may seem like a squeaky clean way to make electricity, dams are not. Building a dam creates large carbon dioxide emissions through:

  • heavy machinery and huge excavations of stone to shape the valley ready to take the dam;
  • vast quantities of concrete to build them;
    • which must be transported along using machines;
    • which releases CO2 while the concrete sets;

Once completed, all dam reservoirs release large amounts of methane, which is 25 times more powerful as a greenhouse gas than CO2. As water sits still in the reservoir for a while, organic matter flowing in via incoming rivers falls to the bottom. This rots and releases methane into the air.

In northern latitudes, dams can produce 5% of the volume of greenhouse gases that would be produced by a conventional power station. In hot countries, they can produce up to 25% of this volume. In future though, it may be possible to reduce or remove much of this methane.

Next: Dams and risk


What's your opinion?

Average rating

Not yet rated

Read comments

NOT RATED conor(: 18-05-11 08:33
you wrote "of of" in the "water power: falling water" section. NOT HAPPY:@
NOT RATED Peep Team 21-05-11 11:04
Ta for spotting the spelling mistake. Fixed now.