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Comment by foobarian | Hacker News Reader

I was curious how it compares to the large nuclear plants and came across this [1] where it turns out the top 7 stations are all hydro. The top one being 22GW! Wild.

[1] https://en.wikipedia.org/wiki/List_of_largest_power_stations

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I really want to like hydro but it has clear negative effects on ecology (namely fish). I am really hoping wind and solar don't affect local ecology as much.

In NV it has really depended on the type of solar but seems anything that takes up large acres of land is going to be an issue. For ground based solar cell arrays we've had issues with the desert tortoise and other animals that it encroaches on their habitat. When you are using the molten salt method the bird population ends up at risk due to the laser like beam of light that gets directed towards the tower. They go so far as to deploy hawks and sounds but inevitably some bird brain gets fried.

There is nothing of meaningful physical scale that can be built that doesn't encroach on some animals habitat. There are no exceptions, whether we're talking about a house, a road, a store, a factory, a power plant, a train line, a commercial office building.

Humans only have two choices: de facto suicide, or encroach.

I vote encroach.

There is plenty of desert and piles of garbage which are great for building solar panels on.

Another aspect often overlooked is shade is very important, there are methods where building solar panels can actually help the environment by providing much needed shade.

You can also build solar panels of the water, theoretically you could build solar panels suspended in the air.

And they don't really require much to hold them down, compared to a wind turbine which needs to basically be a tree.

We just don't try. There is no effort to experiment because everyone is scared to change.

More like, because it's so damn hard to get reasonable rates paid for small developers solar projects power output?

Hydro is mostly (not entirely) tapped out for power generation (not, of course, for pumped storage, which doesn't require rivers). Creating reservoirs is also ecologically damaging, and releases a lot of methane (although I'm not sure how large the impact is relative to the carbon savings, this could be FUD I'm repeating)

Layman's question: don't the reservoirs create a new habitat for fish? They'd be "artificial" in a way but eh, so is everything else. Or is the problem that they all get turned into fish pie in the turbine...

One of the main issues is that dams tend to block access to the upstream spawning grounds for species such as Coho salmon. E.g. see https://www.reuters.com/world/us/save-salmon-us-approves-lar....

Not sure how prevalent they are bit aren't fish ladders built with dams for this exact reason?

https://www.sciencedirect.com/science/article/pii/S092585741...

Yes, but it's very hard to get fish to use them. Some species are almost completely blocked even if there is a ladder.

Fish ladders are expensive and have a fairly large negative impact on yearly electric output. Forcing upgrades makes most dams too expensive, which would mean they get replaced by fossil fueled power plants which can more cheaply operate as backup for wind and solar.

As a result, most hydro power in Europe is in direct violation of environmental laws, but are also given exceptions given the yearly and regular energy crisis.

They don't work for many species. For example, one study found that 3% of American shad were able to use a fish ladder. https://e360.yale.edu/features/blocked_migration_fish_ladder...

Fish ladders are akin to greenwashing.

Imagine in countries like Vietnam/Cambodia/Laos where they dam up rivers for hydro so badly that it prevents downstream flows, wiping out the downstream natural ecology.

They also have wet/dry seasons, so for part of the year everything gets flooded, overruns the dams and wipes out whole villages.

Pretty much a complete eco disaster that few talk about.

> They also have wet/dry seasons, so for part of the year everything gets flooded, overruns the dams and wipes out whole villages.

This implies a degree of incompetence or corruption on the part of the dam designer and/or dam builder.

I won't say such things never happens, but it is what not being able to predict and design around a regular change of season implies.

> This implies a degree of incompetence or corruption on the part of the dam designer and/or dam builder.

Of course it does!

In Laos/Cambodia, the dams are mostly built by China in order to help them build their silk road to Sihanoukville (so that they can have an easier route to Africa). In Vietnam, it is just plain greed since they aren't in as much of a rush to help China.

Unless you ride a motorbike into the furthest remote areas of these countries, like I have, you wouldn't be the wiser. I've see it all.

Compare and contrast:

http://english.scio.gov.cn/m/beltandroad/2022-05/09/content_...

https://www.theguardian.com/cities/2018/jul/31/no-cambodia-l...

Dams are incredible for wet/dry seasons. They allow you to moderate the flow as you fill and release the revivor. It sounds like youre just describing incompetence.

> It sounds like youre just describing incompetence.

I am.

Is that for hydro or water storage though? Surely you want the flow for hydro.

This isn't about storage. They build hydro dams on running rivers.

That’s not how it works. After it fills up you have to let water out of the dammed reservoir at the same rate it flows in (on average) or else it overflows. The issues created are related to sediments and flow consistency. More info in the top response here: https://earthscience.stackexchange.com/questions/18287/do-da...

I don't appreciate the downvote because you aren't listening to what I'm saying.

When it rains, it floods. They (stupidly) build dams for rate of flow during low season (cause it isn't raining)... then the wet season comes and the dams all overflow. Poor construction practices doesn't help either. They also build dam after dam along the same river... I've see 10+ of these things... ends up being a chain of mess when the first one fails.

Just a bit of googling to give you examples:

"Dam design and greed may factor into flood devastation in Vietnam" https://www.refworld.org/docid/58f9ca0c13.html

https://tuoitrenews.vn/news/society/20231012/investigation-u...

https://www.voanews.com/a/vietnam-must-improve-flood-resilie...

Before the dam they'd have around the same amount of water, actually slightly less than that, as the reservoir loses water through evaporation.

Dams don't create water that wasn't there before.

It sounds like they're upset that the dam wasn't oversized to handle flood control in addition to hydropower.

That's a legitimate gripe with public investment and shortsightedness, but the damn aren't going to be making it worse (unless they're managed by morons).

> unless they're managed by morons

Apparently, you've never been to a country like Vietnam. It is a combination of poor education and greed.

A sudden inrush of water from a dam overtopping can be much worse than a consistent flow even if the absolute quantity is the same.

River fish need different habitat than lake fish.

And in many areas, migratory fish are impeded from reaching their spawning grounds. Fish ladders and other contrivances are a poor workaround for an unimpeded flow.

Look at pictures of a hydro power plant reservoir. Look at the water edge when the water level is lower. It’s like a desert.

When the water level goes up and down it kills all life along the edge. That life is an important food source for fish.

That's pretty much how seasonal rivers work & other natural intermittent water reservoirs.

people already mentioned fish, but still water harbors bacteria and generally has lower oxygen levels than turbulent water. also nutrient-rich sediment piles up at the base of the dam instead of getting distributed evenly down the river.

Ah the rabbit hole of HN.

From Wikipedia about the largest dam in the world: 3 georges dam in China.

Mind-boggling size:

"Terrestrial impact In 2005, NASA scientists calculated that the shift of water mass stored by the dams would increase the total length of the Earth's day by 0.06 microseconds and make the Earth slightly more round in the middle and flat on the poles.[104] A study published in 2022 in the journal Open Geosciences suggests that the change of reservoir water level affects the gravity field in western Sichuan, which in turn affects the seismicity in that area.[105] "

Sort by annual generation and it changes things a bit. 2 of the top 7 are then nuclear.

Interesting how the #1 (Hydro dam in China) can put out 60% more than #2 (Brazil/paraguay dam) at max, but only puts out 9% more per year.

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