It popped up in my Facebook stream yesterday and one comment caught my attention: "Okay, but what about the hectares of forest (with actual indigenous people, animals and plants) and farm lands they are destroying every year with dams ?".
Well everyone has to make sacrifices, some have to visit the mall less often, others have to endure their communities literally sink into oblivion [1]. It's all for the planet, even the methane [2][3].
Of course some dams are not so "good" and some are not so "bad," so you have to be specific. Being able to export electricity (think Plan Puebla Panamá) adds very positively into the math, so all the "indios" and bad environmentalists shut up.
What about the new lakes generated by the dams? What about using these lakes as water reservoir needed for agriculture?
There are certainly different kinds of hydropower. Some generating a large lake for a little power output while others in the mountains of an area with heavy rainfall generate a lot of power without flooding a large area. Yet, it seems that all hydropower projects are either labelled "good" or "bad".
The damage caused by hydro-electrical plants is always blown out of proportion.
Dams create huge reservoir of water, which flood a lot of land upstream, causing the river lines to expand.
however people forget to mention that gravity is a zero-sum game. every area that is being rendered unusable upstream results in creation of new area downstream. More often than not these areas are near large cities which are usually located downstream.
Also it opens up new fertile river bed for agriculture.
Now coming back to your question. Sometimes government do not properly compensate the people that are being displaced or take care of the animals etc. But that is a fault of the government and not the science behind hydro-electrical.
>however people forget to mention that gravity is a zero-sum game. every area that is being rendered unusable upstream results in creation of new area downstream.
That's not right. Once the lake is created, nearly the same amount of water will be flowing downstream.
With a dam the water flow is more controlled, so there is less flooding downstream. It's not a simple zero-sum game like the grandparent post said though.
Not necessarily true bc that assumes constant rain. Depending in the inconsistency of rainfall, the water flow downstream will be lumpier due to the resevoir requiring a certain level of water.
The other way round: the reservoir catches excess rainwater and feeds it downstream through dams and power plants, often aiming to catch water to the reservoir and keep constant flow, at least not exceeding the generation capacity (trying to avoid bypass discharge). The reservoir is where the "lumps" are caught and level of water can change considerably.
The absence of lumps, i.e. floods downstream, is of course not always good for nature of the water systems, as in many places the river system ecology is based on having some floods. And specific arrangements need to be made for fish to pass dams and power plants.
> however people forget to mention that gravity is a zero-sum game. every area that is being rendered unusable upstream results in creation of new area downstream.
What? The area taken up by artificial bodies of water is not a zero-sum game. If you build a reservoir which is as large or larger in area as the whole river downstream - conceivably possible in some cases - the river downstream does not vanish or become negative area.
Flood control brought by dams may make the waterways downstream behave differently and lose area, but those impacts aren't all positive either (ecologically or economically).
It may be true that damage caused by hydro-electrical plants is very often blown out of proportion, but I don't follow your logic regarding the areas at all.
> The damage caused by hydro-electrical plants is always blown out of proportion.
Blanket statement. Which hydro-electrical plant? Very important point. That's a point the "let's reduce carbon emission with hydro-power" camp misses all too often.
