Dam impacts: gains and costs
A dam changes the place where it is built. The gains can be big. It makes electricity without burning a fuel, it stores water for farms and towns for dry months, and it can control the river so there are fewer floods. But there are costs too. The lake behind the dam, called a reservoir, covers land where animals lived and where people may have had homes or fields. Fish that swim up the river to lay eggs can be blocked by the wall. Below the dam, the river may carry less mud to farm soil. Engineers and communities weigh the gains and the costs before they build. Far away, the Kariba Dam on the Zambezi River, between Zambia and Zimbabwe, is a well-known example, and people there still study its impacts. We do not blame anyone: we ask what the dam gives and what it takes.
| Gains | Costs |
|---|---|
| electricity without burning fuel | land and habitats covered by the lake |
| water stored for dry months | fish routes blocked |
| fewer floods downstream | less mud for farm soil below |
| Choice | A gain | A cost |
|---|---|---|
| dam | stores water | covers land |
| wind farm | uses little land | needs wind |
Gains and costs. Draw a table with two columns, Gains and Costs. Write two items in each from this lesson. Circle the gain you think is greatest and say why in one sentence. Pick one cost and write a way to reduce it. Then tell a family member what you chose and ask if they agree.