Hydropower is big stuff. 6% of total US electricity and about one fifth of total global electricity come from a dam somewhere on a river. These dams can be as large as Hoover and Three Gorges, or as small as models developed to power individual homes. And, at least, in the United States, they are everywhere. Check out this time series of dam construction in the US over the last two centuries.
Hydropower is pervasive for a reason. In the form of waterwheels, it is one of the oldest forms of energy production. It is also one of the most convenient. Think about it. Humans don’t necessarily settle where there is abundant oil, gas or coal. While sunlight and fresh air are a plus, you can find large numbers of people in regions with seasonally erratic light availability, frequent clouds, or stagnant air. Even wood isn’t necessarily a prerequisite for settlement. But water? True, there have always been desert cultures, and true, many areas of current high population density are experiencing severe water stress. Historically, however, the water source for a city or town, as long as it had some kind of current, was likely a power source as well.
Hydropower is, in theory, good for the developing world. It requires no imported fuel, can be done with fairly simple technology, has a relatively low carbon footprint, and emits none of the other atmospheric pollutants associated with wood/fossil fuel burning (particulate matter, sulfates, gasoline additives, etc.). The “in theory” is an important part - as the UN report linked to demonstrates, a big dam has the potential to upend entire communities and effectively dispossess large numbers of people, and a poorly sited or poorly designed dam can bring chaos to a region with little power generation to show for it. However, like any other development strategy, there are pluses and minuses to consider in dam construction, and a well-executed project can do great things for a community or a country.
Things are a little more clearcut when we talk about dams in developed countries. Think back to that video of dam proliferation. Pretty extensive network, right? In the United States, anyway, it can be said that if it’s dammable, it’s dammed. Few dams have been constructed in the last few decades, because there is simply nowhere to put them. Meanwhile, technical advances in dam construction have left many of the older, smaller dams obsolete. At this point, rather than generate meaningful amounts of power, these dams serve only to block off rivers and streams to migrating fish.
I might cover this in more detail later on, but here’s a crash course in migratory fish biology. Some fish live, reproduce and die in the same kind of water - a minnow may spend its entire life in one pond, and a clownfish is unlikely to leave its marine habitat. Other fish, the diadromous fish, divide their life cycle between marine and riverine/estuarine habitats (saltwater and freshwater). Anadromous fish are born in freshwater habitats, spend most of their adult lives in saltwater, and return to freshwater to spawn. Catadromous fish, meanwhile, are born in saltwater habitats, spend most of their adult lives in freshwater, and return to saltwater to spawn. Diadromous species need open rivers in order to migrate, reproduce and maintain healthy populations. Migrating fish serve as food sources for marine, freshwater and terrestrial animals (the iconic bear eating salmon springs to mind), in addition to providing commercially and culturally important fisheries.
This is where I cop to some bias. For the last few years, I’ve been a volunteer with the (Maine) Penobscot River Restoration Project, which seeks to remove several obsolete dams from the Penobscot and open a large expanse of river to migrating fish. It’s not a pipe dream. A similar project on the Kennebec River (also in Maine) saw the recovery of a number of migratory fish species, including striped bass and sturgeon. The alewife runs that once defined so many New England rivers have returned to the Kennebec, as have healthier populations of migratory fish dependent species like bald eagle, osprey and bears. The success of the project inspired the work currently taking place on the Penobscot River, and continues to inspire dam removal projects throughout New England. Most of the dams slated for removal haven’t generated power in years. Those that have can be replaced by improvements and upgrades to the remaining dams.
I’m not saying that all dams are evil and should be removed. Supporting a growing human population and a rising standard of living is a complex process, one that comes with a seemingly infinite array of trade offs. Here in the developed world, however, we live with a legacy of earlier, less efficient means of producing power (among other things). Removing “development dinosaurs” like obsolete dams allow us to have our cake and eat it too, in a way. Communities along the Kennebec still get the same amount and quality of electricity they once did, and the percent coming from hydropower hasn’t changed. But now, in addition to electricity, locals get to enjoy eagles, osprey and the kind of fishing that hasn’t existed on the river in over a century. It’s an imperfect universe, but I’d call that a best of both worlds outcome.
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