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goda90 2 days ago [-]
A rewilding organization bought some forest land, downstream from a dam, that used to get seasonal flooding before the dam was built and made an agreement with the dam operators to do artificial seasonal flooding via ditches they dug. The flooded forest has the effect of providing fish nurseries so hatchlings have a chance to hide and grow before the water recedes and they have to return to the river.
I think it's a testament that human activity and nature don't have to be all or nothing, but we need to consider and mitigate the impact of our actions and always leave space for nature.
worldsayshi 2 days ago [-]
Exactly I don't get why we can't figure out and prioritize allowing fish to pass around the dams.
RajT88 2 days ago [-]
We can. One presumes it is less efficient than just removing the dam. It is more work versus less work - fish ladders and the like.
jaggederest 2 days ago [-]
Not only that, but a lot of these dams are not even in use any more, so doing additional work doesn't make much sense. Remove the dam, remove the problem, instead of duct tape solutions.
RajT88 2 days ago [-]
Fisherman like them because fish bunch up beneath them. Despite the overall populations being higher once all the dams are gone.
There is an aspect of property value as well - dams maintain a certain river level and removal may impact how nice people's river houses are. (Source: Dam near me partly removed, turned into a kayak course.)
idontwantthis 2 days ago [-]
There are many dams with fish ladders or even fish cannons.
Because the government lays claim to anything and everything involving water so you can't "just" buy a bunch of adjacent land and start building a fish ladder around an old dam without going through insanely costly bullshit that everyone here cheers for because the peddlers of the bullshit act like it only ever gets used to stop DuPont from dying the river blue or whatever. And of course you can't touch the dam either without comparable cost because of "you touch it you bring it up to modern code" rules and whatnot. And this stuff isn't just a matter of going through the motions. Without friends in high places "helping" have to fight for every inch with lawyers and whatnot because these process pathways are designed to be exclusionary and expensive because they're designed to stymie industry.
So basically all these 100-200yo dams are stuck in this limbo where doing anything with them is a non-starter until they're at the point the government decides they could fail any day now and starts pulling out stops.
causesothere 1 days ago [-]
One, you are obviously incorrect per the other reply. Two, theres a lot more DuPonts "dying the river blue" than there are good samaritans building fish ladders.
cucumber3732842 1 days ago [-]
>One, you are obviously incorrect per the other reply
Amazing how people just believe assertions because they like them. Anyway, as I told him the typical dam we're talking about here is some mill pond dam that's too small to be federally regulated.
> Two, theres a lot more DuPonts "dying the river blue" than there are good samaritans building fish ladders
If you'd put down your ideology for a second you'd realize that there's more BigCos running through the approval processes to do their sketchy things because the process was built for them. The fish ladder people see the requirements (like non-starter remediation bonds) and realize it's not for them.
causesothere 5 hours ago [-]
I own hundreds of acres of forest land with watershed stream habitat. I work on conservation efforts for it, including working with governmental orgs. I know all about the processes involved. Don't lecture me on it or assume I'm talking out of my ass.
idiotsecant 1 days ago [-]
Yeah this post has no idea wtf it's talking about. Dams are relicensed routinely by federal regulators and when they are they are routinely required to build in fish passage. If there's a dam blocking fish passage that's the path to fix it.
cucumber3732842 1 days ago [-]
You are the one who has no idea what you're talking about and you're misleading by omission because I dared say anything negative about government.
The mean, median and modal dam being removed is a low head dam constructed in the early 20th century or before to create a mill pond for some factory. They are almost never federally regulated because they almost never meet the height/size requirements.
aaron695 2 days ago [-]
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glenstein 2 days ago [-]
More good news: after years of fighting, Brookfield Renewable agreed to sell four dams on the Kennebec River which will let Atlantic Salmon go back up river to their spawning territory. This just happened in 2025 and could be a bigger breakthrough than the massive alewife restoration that the article mentions.
My understanding is that the first few victories on this were very very hard but it seems to have created a precedent and a growing example emulated across the country.
Bittersweet. Because the reason all those dams are able to be sold is because the textile industry and paper industry that used to rely on them has all moved to Asia and Canada, decades ago, and now these mill towns are depressed drug dens
not_kurt_godel 2 days ago [-]
We also shouldn't really be removing hydropower at this point in time from a net zero/global warming perspective. It is orders of magnitude less environmentally harmful than generating electricity with fossil fuels, and one of two carbon-neutral sources of significant amounts of baseload power at scale along with fission nuclear.
qwytw 1 days ago [-]
a ~5HW hydropower is insignificant and can be replaced by a handful of wind turbines and solar panels. Not sure if it's worth sacrificing local biodiversity for that.
not_kurt_godel 1 days ago [-]
I did some quick napkin math on the net economic benefit, including carbon pollution and local economic benefit, of 3 scenarios:
1. Keep dam: -$2M to -$10M
2. Dam removal with 5 MW capacity replaced/absorbed by natural gas plants (no solar/wind/BESS): -$28.3M to -$249.8M, depending on whether you use the EPA's $190/tCO2 cost of damage or $1000/tCO2 DAC remediation.
3. Dam removal with 5 MW solar/wind/BESS replacement: -$3.5 to -$25M
In other words, removing the dam without equivalent solar/wind/BESS immediately in place is a net negative for society (and even then, keeping the dam might be neutral or still better).
gkanai 1 days ago [-]
> net negative for society
You did not calculate the impact on the salmon population since dams were added to the Kennebec since 1837. Both the impact on the salmon themselves as well as all of the other animals and people who relied on that salmon fishery.
It's certainly a lot larger than the benefits of the dams in my calculation.
Ok, I found a study estimating a net willingness to pay per citizen for this type of ecological restoration at ~$72.31/per person/year. If we assume 100,000 people derive this level of benefit over a 30-year time horizon (same as I used for the previous numbers) that yields $21,693,000 which brings the removal WITH immediate solar/wind/BESS replacement scenario on par or marginally better than keeping the dam as is.
But even then, I believe that is being overly generous to the dam removal because electricity demand has been rising steeply recently and is projected to continue doing so. Until we are meeting 100% of current and future demand with new renewable energy, every existing carbon-neutral source that gets removed is creating a gap in future demand that will be partially filled by new fossil fuel generation and therefore incurring many of the same associated negative societal costs.
glenstein 19 hours ago [-]
I would flip the question on its head and ask why the response to uncertainty is to default to an assumption of zero. Environmental benefits are notoriously hard to calculate and it's unfair to weaponize that difficulty as if it confirms the default assumption should be zero. I also don't think the calculation needs to hinge on one-for-one timed tradeoffs in the form of "this windmill exists to replace power from that dam" or assume that backfill is 100% fossil fueled, given that solar is now arguably the most rapidly deployed form of new generation.
It's not that the cost never matters but I think if the cost is really just $25MM for a transformatively beneficial environmental impact that has equivalent no alternative, in exchange for scaling back a fungible resource, is a no-brainer.
sintaxi 2 days ago [-]
absolutely agree. hydropower is god-tier technology.
qwytw 1 days ago [-]
Most of those small and medium hydropower plants generate near insignificant amounts of electricity, even if you damn all the non major rivers you can (and destroy all the surrounding ecosystems) it would be hardly noticeable.
not_kurt_godel 21 hours ago [-]
My napkin math disagrees. Small/medium hydro (<100 MW) appears to account for ~1.7% of annual US grid energy output. If we replace that with fossil fuel generation and account for the cost of dam decommissioning, account for estimated benefit of ecosystem restoration in terms of quantified dollars willing to pay by benefiting citizen, and net annual CO2 cost I come up with an annual cost to society of removal of small/medium hydro dams between $1.7B/year on the low and $41.7B/year on the high end. Happy to show detailed assumptions and calculations if desired. But tl;dr fossil fuel generation is very, very bad and replacing even comparatively small amounts of carbon-neutral generation with it results in a significant societal net negative.
ch4s3 2 days ago [-]
These dams are in the north east, those industries moved to the south long before moving to Asia. My grandmother worked in one of those mills that moved south during WWII. Many moved even deeper south after legally enforced segregation ended.
twright 2 days ago [-]
This sounded familiar and then I realized I had read the same article a few weeks ago. This is some strange syndication I would propose changing the link to this one: https://biographic.com/death-by-a-thousand-dams/ it’s also way better layout and fewer ads.
metalman 2 days ago [-]
Small dams, hydropwer and fish can co exist, though there is a loss in 'efficiency' in extracting the free power embodyed in flowing water.
Undershot wheels need to be relativly large and also leave room for fish to swim underneath them, but thats it, the wheel turns, the fish swim on by.
The real problem are 'mid sized' hydropower
turbines which cut of many large water sheds to fish migration, and I have been involved with water protectors in various ongoing attempts to remediate or remove varios dams and 'water control' aperatus, and the push back from entrenched intrests is rabid, anti everything but wealth and privlage, and the 'legal rights' to water sheds underpins many
an unearned fortune, and perfectly illustrate the very ancient concept of Hydraulic Despotism.
hinkley 2 days ago [-]
As the article alludes, the blueprint/precedent for this kind of work was set in the Klamath river basin in western Oregon. The local tribes deserve a tip of the hat for pushing through the lobbying and suits to get this process started.
And a hat tip to all of the people who made the projects as successful as they have been in saving fish populations. IIRC, they ran into some surprises with volunteer fish which reduced the amount of hatchery fish they anticipated needing.
m_herrlich 2 days ago [-]
Good for the fish but as winters get warmer these dams will be useful to store rain that doesn't stay put in the mountains as winter snow. This might mean more summer droughts. Also a nice clean source of power. I would rather see fish ladders.
evolve2k 2 days ago [-]
You actually want to restore the river to be more resilient as the earth warms, fish returning empowers many other parts of a river ecosystem.
Install dedicated water tanks to store water, evaporation rates are much less.
missmewiththatl 2 days ago [-]
Most of the folks on the forum are not engineers, you can't expect them to understand the downstream effects of their decisions.
fodkodrasz 1 days ago [-]
They are prompt engineers.
fsckboy 2 days ago [-]
so, the engineers who built the dams did understand the downstream effects of their decisions? and they did it anyway?
conductr 2 days ago [-]
Likely yes. Different times, different sensibilities. But also there’s always a range of opinions even among experts. How long did it take medicine to agree on tobacco use and whether an egg is healthy?
cucumber3732842 1 days ago [-]
They knew what would happen. They just didn't have modern values. People would rather make them out to be stupid than admit that anyone at any point looked at the tradeoff and decided the dam would benefit everyone enough more than the ecosystem to be worth it.
cyberax 2 days ago [-]
> You actually want to restore the river to be more resilient as the earth warms, fish returning empowers many other parts of a river ecosystem.
Dams can make rivers more resilient.
jessekv 2 days ago [-]
Small dams raise the temp of the water and decrease the dissolved oxygen, so removing the dams can improve ecological resilience in a warming climate.
andrejserafim 2 days ago [-]
Several countries in Europe are planning to build more damns after the last very dry summer.
cucumber3732842 2 days ago [-]
Yes and no. Most of the dam removals are 100-200yo old low head damns that fed mill ponds so they weren't really holding anything back when there was high demand.
Thaaaaaat said, moving from "slap up a damn somewhere" based stormwater management to local stormwater management is probably gonna go down in history as one of the biggest boondoggles in the history of environmentalism in the wet eastern half of the country (the desert west where aquifer replenishment is a concern is a different story)
bobthepanda 2 days ago [-]
At this point there isn’t much additional space you could dam without adverse impacts. The flood barriers for New York at the mouth to the Atlantic were rejected both for being too costly and for screwing everyone outside the dams.
2 days ago [-]
Alive-in-2025 1 days ago [-]
Lot of good postings here, I'm excited that people are noticing the multiple efforts to help nudge fish passages back to life, where the remaining fish are barely hanging on in some places.
It’s more about money as well. There are a lot of private dams that are effectively abandoned and are a threat to the area if they aren’t updated or removed. Same for the publicly maintained ones. Most of them require budget and tax dollars to maintain and a removal is much cheaper long term.
habinero 2 days ago [-]
The kinds of dams involved in these projects aren't doing anything useful. They're mostly small and obsolete and/or at the end of their lifespan. They were generally built before we had a power grid.
You can't just leave them, they'll eventually fail and it costs way too much to bring them up to code and maintain them.
This is one of the very rare "everyone wins" stories. Environmentalists, cities, water districts and wildlife all come away better.
cucumber3732842 2 days ago [-]
Abutting landowners get un-fucked as the jurisdictional wetland that was formerly upstream of the dam recedes. It really is a win all around.
ZYbCRq22HbJ2y7 2 days ago [-]
Depends on the type of water if this a net benefit, but it roughly should be better than the current state of things.
Nothing will bring waters back to their pre-industrial state though.
3 days ago [-]
jimnotgym 1 days ago [-]
Interestingly this thinking has carried over to the UK. And as is often the case, people don't consider the scale changes and second order effects.
'Removing barriers to salmon migration' became a huge deal about 20 years ago, with conservation bodies removing weirs. Yes weirs not dams. Old Mill weirs, for instance, that were there when salmon stocks were high.
A lot of money has been spent, especially in the River Wye, which wriggles between Wales and England. The salmon stocks have plummeted, and got worse since they started.
The thing is Salmon could jump weirs in a flood. That is their evolutionary advantage. They had access to tributaries that no other fish could get too. Now Salmon can get their, along with Barbel, who eat fish eggs... and are not native to the Wye. Just saying.
One 'expert' (at fundraising at least), said 'Salmon could only cross these barriers in high flows' which is fine, because Salmon only run the river at all at high flows.
Weirs also provided varied habitat, and more oxygenated water... that is now lost.
I went to a seminar lead by two of these groups. One gave a presentation about all the dead trees they had removed from the river to 'remove barriers'. The second speaker talked about the dead trees they put in the river to create fish nurseries. I seemed to be the only person that find this absurd.
Now the barrier removal people are claiming success. As in they successfully raised the money and removed the 'barrier', one presumes. Salmon stocks have got worse.
There is more, but that was sad enough on its own
jessekv 1 days ago [-]
In the great lakes you have low-head dams keeping lampreys at bay:
But oxygenation not really an advantage of low-head dams, when the dam is often contributing to the oxygen depletion in the first place. Free-flowing streams are typically adequately oxygenated.
thewhitetulip 1 days ago [-]
Outnof curiosity: if you have no dam then how do you manage water for the country?
herbst 1 days ago [-]
Some countries have healthy ground water I guess
ekaryotic 23 hours ago [-]
israel does desalination on a massive scale.
BatchJob 2 days ago [-]
Is it not possible to at least consider that if the populations came back so fast that in fact the environmental damage to the populations was overstated to perhaps mythical proportions?
NegativeLatency 2 days ago [-]
You might be conflating the west coast dams that are killing the orcas?
Also once it’s gone it can’t come back
notabotiswear 3 days ago [-]
> Many NOOMBYs consider local dams indispensable ties to their community’s past; in Billerica, some town officials have objected to the demolition of the Talbot Mills Dam on the grounds that “it has long served as a symbol of the Industrial Revolution” that remains “unquestionably one of the major focal points in the area.”
I used to hate the "but what about historical site upstream?" argument often used against dams. The prioritisation of a few tombs and piles of stone over what would improve the lives of thousands to tens of millions living now. It's kinda ironic seeing the same asinine argument being used from the other side...
That said, reducing dams to just hydroelectric generation is probably going to skew the narrative to the wrong direction.
monomania 2 days ago [-]
They are also very difficult, and very expensive, to maintain as they age. There is a small hydro damn near where I live that predates WWII and the county/state cannot find anyone who wants to take it over because of the expense in repairing it. This is in part due to seismic retrofitting which needs to happen, but also a variety of other factors, including being built basically on silt, having a public road on top which people need to get to their homes, and simply updating the aged equipment which has been on its last leg for a while.
What's more, the dam installation changed the local water table level, and residential wells drilled since the 1940's only had to go down so far. If the dam is removed, all these wells will dry up, and the state is beginning to make it difficult to drill new wells, and they certainly don't want to shell out to install plumbing to unincorporated communities which don't vote for the majority party anyway.
Another dam nearby held a massive amount of water for one of the bigger cities in the state. This is on the west coast, and if we get the Big One, it'll flood a populated area with hundreds of thousands of people. So they've had to draw down on the water levels and it's basically useless now, but deconstructing the dam would probably be a project requiring federal money, and since it's an earthen dam in a seismic zone there isn't really any retrofitting that you can do to fix it.
Basically, dams will give you some cheap electric and a water supply for a while but after 50-70 years they're a huge liability.
chihuahua 2 days ago [-]
I think the fact that the same bogus argument is used both against dam building and against dam removal shows that it's bogus and not compelling. When someone is against something, they will use whatever argument they can concoct. Saying that something is historically significant seems to work great. As if history is some god that must be served no matter what.
jordanb 2 days ago [-]
Many of these weirs are extremely dangerous to swimmers. When I was young there was an incident on a nearby weir (obsolete lowhead dam) where one person got trapped and drowned and then four people who jumped in to rescue him also drowned.
Not be insensitive to death, but this not really a damning case against the structure itself. Hazards to swimmers are pretty common and can happen with any hydraulic structure and often without. Especially in the latter cases the, expected response are warning and prohibition. Those caused by a structure should be even easier to manage because they are predictable.
That this hazard is tied to a structure with no utility is a specific scenario. But in another where the structure does serve a purpose then restricting one recreational activity in its vicinity may be an acceptable cost. Par exemple, would you be against fencing a substation or prohibiting kite/drone flying near high voltage lines?
jordanb 1 days ago [-]
There are far less dangerous dam designes. Again if you read the article or watch the video the weir creates a hydraulic "trap" downstream of it from which escape is essentially impossible.
notabotiswear 1 days ago [-]
I am aware of weir hydraulics and no one is denying the hazard they create. I am saying that everything generates a hazard and managing it is always going to be required.
That said, any structure spanning the width of a channel alters the flow in ways that are hazardous to swimmers and boats.
jhide 2 days ago [-]
What do dams do besides hydroelectric generation?
ddxv 2 days ago [-]
Dams create large bodies of water that change ecosystems and provide focal points for human communities. They certainly do more than just hydroelectric.
An example would be Lake Pillsbury in Northern California which the dam has not done hydroelectric for decades but the fight to prevent demolishing the dam has had plenty of local support.
lukeify 2 days ago [-]
Flood control and water storage for agriculture in drier summer months are the big ones.
toast0 2 days ago [-]
In addition to other answers, dams are sometimes used for mechanical power without generating electricity. More likely to be historic use than current use, but also likely to be a candidate for removal for fish habitat.
tialaramex 1 days ago [-]
Right, it's like with literal wind mills (not wind turbines). In a very few cases it's part of a museum showing how mechanical power was used to mill flour, or power weaving machines, or whatever. Getting rid of literally every single one would be a mistake. But in the other cases they're just left to decay and so we should remove them and restore what was there before.
pfdietz 2 days ago [-]
They fill up with sediment and emit large amounts of methane from decaying organic matter.
hinkley 2 days ago [-]
The one Andrew Carnegie and his friends mismanaged and killed thousands of people with was for recreation.
darksaints 2 days ago [-]
I think you probably meant Andrew Carnegie
kps 2 days ago [-]
How to Wet Friends and Inundate People
MadrasTh0rn 2 days ago [-]
I do not support removing hydropower
forrestthewoods 2 days ago [-]
Dams and hydro are renewable energy. But they sure ain’t “clean” energy.
kibwen 2 days ago [-]
The vast majority of the 2,000+ dams mentioned in the article are barely even energy by modern standards, each putting out somewhere on the order of a single wind turbine, if they're even still hooked up at all.
cyberax 2 days ago [-]
To add a bit of a negative: dam removal has far less success in salmon restoration. The Elwha dam removal resulted in no native salmon runs. All the salmon in Elwha are still raised in hatcheries (they have clipped fins, so that's easy to track).
The biggest success so far was in the Klamath River watershed.
PeterHolzwarth 2 days ago [-]
Hm, I dunno - this article makes it sound like recovery is happening and ongoing:
> While annual estimates of the proportion of hatchery-origin natural spawners (pHOS) were initially 94-97% during and immediately following dam removal (2014-2019), pHOS declined to 82-85% during 2020-2024 (Weinheimer et al. 2022, WDFW unpublished).
And the absolute numbers are also not that great.
Elwha dam removal was a no-brainer as it was entirely useless. But it does cast doubt on the efficacy of larger dam removal projects, they are not necessarily going to result in automatic recovery.
WA is also spending about $10B on improving culverts on smaller streams. So far this hasn't resulted in meaningful effects on salmon runs. These moneys would be much better spent on other environmental projects.
PeterHolzwarth 2 days ago [-]
Thanks for expanding on the topic, I appreciate it.
rrr_oh_man 2 days ago [-]
> Klamath
Don't Tread on the Bear!
_eht 2 days ago [-]
[dead]
threethirtytwo 2 days ago [-]
But also less energy created by dams means energy is now likely offset by energy generated by greenhouse gases.
lukeify 2 days ago [-]
Most of these dams were either in disrepair, had geotechnical problems, or were sufficiently silted up they didn't generate much power anyway. A few dozen rooftop solar installations probably generate more power.
galago 2 days ago [-]
A lot of the low hanging fruit is still dams that were made for non-hydroelectric, non-drinking, even non agriculural purposes. In the Northeast there are 19th century dams that originally powered mills before steam power. The barriers in some of these cases are just the cost of removing the dam, which can be substantial if it borders private property. Some of the flood control functionality is no longer necessary, because it can be migated and in some cases the land can just be bought out.
pfdietz 2 days ago [-]
Many of these small dams are also safety hazards because of the very hazardous horizontal vortex they create as water flows over them. Swimmers are caught in this and drown.
Rodmine 1 days ago [-]
The country which sold "climate change" to the world to try to push their "clean-tech" energy market products as a defiance of OPEC embargo, is now trying to push their "care" for fish to discourage hydropower.
tonymet 2 days ago [-]
The biggest dam removal project, which has thankfully stalled , is planning the removal of about 6 dams along the Snake River (Idaho & Eastern WA), which provide flow regulation (river bank control) , transit (about 10% of the US grain) and electricity.
Removing these dams will exacerbate the crisis in baseload generation, and add hundreds of thousands of trucks a year to the Columbia gorge.
These dam removal projects are driven by anti-growth misanthropes who hate prosperity and aim to dismantle infrastructure.
For the fish!
krylonmae 2 days ago [-]
That’s great until your land floods
wiether 2 days ago [-]
> In Plymouth, Massachusetts, a former dam has been converted to a bridge that lets fish pass unimpeded beneath it
That's a hell of an ugly bridge!
They tried to make it look "natural" with the rock tiles but there's absolutely nothing natural about it.
A plain concrete bridge would have been less of an eyesore.
lukeify 2 days ago [-]
In your opinion.
It's clearly being empathetic to the area's history, and it's taken from a vantage point that you won't often see anyway.
csallen 2 days ago [-]
I clicked the story just to see the very ugly bridge in question, and it turned out I think it's quite attractive
chihuahua 2 days ago [-]
Yeah, well, you know, that's just like, your opinion, man.
It's a bridge that looks like it's made from stone. It looks slightly different from other bridges. It's not bad. There are probably many eyesores in the surrounding towns that look much worse.
https://youtu.be/qcVMX32c0io
I think it's a testament that human activity and nature don't have to be all or nothing, but we need to consider and mitigate the impact of our actions and always leave space for nature.
There is an aspect of property value as well - dams maintain a certain river level and removal may impact how nice people's river houses are. (Source: Dam near me partly removed, turned into a kayak course.)
It's absurdly funny/weird/scary
https://www.youtube.com/watch?v=eGzdOpCisnQ
https://m.youtube.com/watch?v=V6CLumsir34
So basically all these 100-200yo dams are stuck in this limbo where doing anything with them is a non-starter until they're at the point the government decides they could fail any day now and starts pulling out stops.
Amazing how people just believe assertions because they like them. Anyway, as I told him the typical dam we're talking about here is some mill pond dam that's too small to be federally regulated.
> Two, theres a lot more DuPonts "dying the river blue" than there are good samaritans building fish ladders
If you'd put down your ideology for a second you'd realize that there's more BigCos running through the approval processes to do their sketchy things because the process was built for them. The fish ladder people see the requirements (like non-starter remediation bonds) and realize it's not for them.
The mean, median and modal dam being removed is a low head dam constructed in the early 20th century or before to create a mill pond for some factory. They are almost never federally regulated because they almost never meet the height/size requirements.
My understanding is that the first few victories on this were very very hard but it seems to have created a precedent and a growing example emulated across the country.
https://themainemonitor.org/dams-sale-salmon-return-kennebec...
1. Keep dam: -$2M to -$10M
2. Dam removal with 5 MW capacity replaced/absorbed by natural gas plants (no solar/wind/BESS): -$28.3M to -$249.8M, depending on whether you use the EPA's $190/tCO2 cost of damage or $1000/tCO2 DAC remediation.
3. Dam removal with 5 MW solar/wind/BESS replacement: -$3.5 to -$25M
In other words, removing the dam without equivalent solar/wind/BESS immediately in place is a net negative for society (and even then, keeping the dam might be neutral or still better).
You did not calculate the impact on the salmon population since dams were added to the Kennebec since 1837. Both the impact on the salmon themselves as well as all of the other animals and people who relied on that salmon fishery.
It's certainly a lot larger than the benefits of the dams in my calculation.
Ok, I found a study estimating a net willingness to pay per citizen for this type of ecological restoration at ~$72.31/per person/year. If we assume 100,000 people derive this level of benefit over a 30-year time horizon (same as I used for the previous numbers) that yields $21,693,000 which brings the removal WITH immediate solar/wind/BESS replacement scenario on par or marginally better than keeping the dam as is.
But even then, I believe that is being overly generous to the dam removal because electricity demand has been rising steeply recently and is projected to continue doing so. Until we are meeting 100% of current and future demand with new renewable energy, every existing carbon-neutral source that gets removed is creating a gap in future demand that will be partially filled by new fossil fuel generation and therefore incurring many of the same associated negative societal costs.
It's not that the cost never matters but I think if the cost is really just $25MM for a transformatively beneficial environmental impact that has equivalent no alternative, in exchange for scaling back a fungible resource, is a no-brainer.
And a hat tip to all of the people who made the projects as successful as they have been in saving fish populations. IIRC, they ran into some surprises with volunteer fish which reduced the amount of hatchery fish they anticipated needing.
Install dedicated water tanks to store water, evaporation rates are much less.
Dams can make rivers more resilient.
Thaaaaaat said, moving from "slap up a damn somewhere" based stormwater management to local stormwater management is probably gonna go down in history as one of the biggest boondoggles in the history of environmentalism in the wet eastern half of the country (the desert west where aquifer replenishment is a concern is a different story)
In Washington State we have some of this happening too. A few years ago the long delayed projected to remove the damn on the Elwha on the Olympic Peninsula finally happened - https://en.wikipedia.org/wiki/Restoration_of_the_Elwha_River.
You can't just leave them, they'll eventually fail and it costs way too much to bring them up to code and maintain them.
This is one of the very rare "everyone wins" stories. Environmentalists, cities, water districts and wildlife all come away better.
Nothing will bring waters back to their pre-industrial state though.
'Removing barriers to salmon migration' became a huge deal about 20 years ago, with conservation bodies removing weirs. Yes weirs not dams. Old Mill weirs, for instance, that were there when salmon stocks were high.
A lot of money has been spent, especially in the River Wye, which wriggles between Wales and England. The salmon stocks have plummeted, and got worse since they started.
The thing is Salmon could jump weirs in a flood. That is their evolutionary advantage. They had access to tributaries that no other fish could get too. Now Salmon can get their, along with Barbel, who eat fish eggs... and are not native to the Wye. Just saying.
One 'expert' (at fundraising at least), said 'Salmon could only cross these barriers in high flows' which is fine, because Salmon only run the river at all at high flows.
Weirs also provided varied habitat, and more oxygenated water... that is now lost.
I went to a seminar lead by two of these groups. One gave a presentation about all the dead trees they had removed from the river to 'remove barriers'. The second speaker talked about the dead trees they put in the river to create fish nurseries. I seemed to be the only person that find this absurd.
Now the barrier removal people are claiming success. As in they successfully raised the money and removed the 'barrier', one presumes. Salmon stocks have got worse.
There is more, but that was sad enough on its own
https://publibrary.sec.usace.army.mil/api/download?id=52f6cb...
But oxygenation not really an advantage of low-head dams, when the dam is often contributing to the oxygen depletion in the first place. Free-flowing streams are typically adequately oxygenated.
Also once it’s gone it can’t come back
I used to hate the "but what about historical site upstream?" argument often used against dams. The prioritisation of a few tombs and piles of stone over what would improve the lives of thousands to tens of millions living now. It's kinda ironic seeing the same asinine argument being used from the other side...
That said, reducing dams to just hydroelectric generation is probably going to skew the narrative to the wrong direction.
What's more, the dam installation changed the local water table level, and residential wells drilled since the 1940's only had to go down so far. If the dam is removed, all these wells will dry up, and the state is beginning to make it difficult to drill new wells, and they certainly don't want to shell out to install plumbing to unincorporated communities which don't vote for the majority party anyway.
Another dam nearby held a massive amount of water for one of the bigger cities in the state. This is on the west coast, and if we get the Big One, it'll flood a populated area with hundreds of thousands of people. So they've had to draw down on the water levels and it's basically useless now, but deconstructing the dam would probably be a project requiring federal money, and since it's an earthen dam in a seismic zone there isn't really any retrofitting that you can do to fix it.
Basically, dams will give you some cheap electric and a water supply for a while but after 50-70 years they're a huge liability.
https://practical.engineering/blog/2019/3/16/drowning-machin...
That this hazard is tied to a structure with no utility is a specific scenario. But in another where the structure does serve a purpose then restricting one recreational activity in its vicinity may be an acceptable cost. Par exemple, would you be against fencing a substation or prohibiting kite/drone flying near high voltage lines?
That said, any structure spanning the width of a channel alters the flow in ways that are hazardous to swimmers and boats.
An example would be Lake Pillsbury in Northern California which the dam has not done hydroelectric for decades but the fight to prevent demolishing the dam has had plenty of local support.
The biggest success so far was in the Klamath River watershed.
https://washingtonfishinghub.com/the-elwha-salmon-runs-recov...
https://www.elwha.org/wp-content/uploads/2026/01/Spatial-Spa...
> While annual estimates of the proportion of hatchery-origin natural spawners (pHOS) were initially 94-97% during and immediately following dam removal (2014-2019), pHOS declined to 82-85% during 2020-2024 (Weinheimer et al. 2022, WDFW unpublished).
And the absolute numbers are also not that great.
Elwha dam removal was a no-brainer as it was entirely useless. But it does cast doubt on the efficacy of larger dam removal projects, they are not necessarily going to result in automatic recovery.
WA is also spending about $10B on improving culverts on smaller streams. So far this hasn't resulted in meaningful effects on salmon runs. These moneys would be much better spent on other environmental projects.
Don't Tread on the Bear!
Removing these dams will exacerbate the crisis in baseload generation, and add hundreds of thousands of trucks a year to the Columbia gorge.
These dam removal projects are driven by anti-growth misanthropes who hate prosperity and aim to dismantle infrastructure.
For the fish!
They tried to make it look "natural" with the rock tiles but there's absolutely nothing natural about it.
A plain concrete bridge would have been less of an eyesore.
It's clearly being empathetic to the area's history, and it's taken from a vantage point that you won't often see anyway.
It's a bridge that looks like it's made from stone. It looks slightly different from other bridges. It's not bad. There are probably many eyesores in the surrounding towns that look much worse.