What are some issues for and against building dams on rivers?

Answer 1

This is a good question!

Reasons FOR building dams -
- renewable energy source (hydro-electricity)
- recreation (boating, fishing, etc. on the reservoir)
- water supply (surface water is better than using wells for water)
- can also be source of cooling water for other power plants
- can have more stable water supply for irrigated farming
- flood control

Reasons AGAINST building dams -
- flooded area can displace people, culture, and animal habitats
- dam will trap sediment from being normally carried downstream
- will affect the acquifiers downstream (may have springs go dry)
- could keep other communities from getting needed water downstream
- can cause increased erosion downstream
- eventually they will need either to be maintained or be "decomissioned" or removed when sediment has filled in the area of the lake and THAT will be expensive.
- generally have large cost over-runs due to delays in the construction schedule
- generally the irrigation effectiveness is much below the plan
- for dams built in the tropics, they can increase the occurance of some diseases.
- the larger surface area of the water behind a dam can increase evaporation loss of water on a river

I hope these ideas help you understand some of the issues with making a decision on building a dam or not.