Why people build Water Dams? And How they Work?

Question

Please answer in Science Terms

Answer 1

There are several benefits of building water dams:

Firstly they can control the flow of the rivers they dam, which prevents flooding to lower regions of the river. I don’t really think this needs explaining scientifically!

Secondly they can create huge water stores for times of drought, which means that water will come out of your tap and farmers can water their crops all year round.

Finally they can be used for hydroelectricity production, when the dams are built huge turbine rooms are constructed, usually within the dam, these rooms contain turbines which are powered by the effects of gravity on water (the dam holds loads of water then you channel this water through pipes to a turbine and then out of the other side at the bottom of the dam, all of the water inside the dam wants to get out through this pipe due to gravity pushing down on the surface of the dammed water) the turbines are connected by huge gears to generators which when turned produce electricity which if feed back into the national grid.

The final benefit is how most countries justify the huge cost of dam building.

Don’t forget that there is also a downside to dams, including the huge ecological side effects, the displacement of animals and people and also those that depend on yearly flooding of low lands like some farmers (the Nile is a good example of this). Also there is the huge cost of building a dam, the one which has been built on the Yangtze-Jiang (I think that’s spelt correctly) is due to cost in excess of 25 billion US dollars.