Time and again, I’ve heard people claim that the Northwest’s energy system is "greener" than in other parts of the country, because the region generates so much power from hydroelectric dams (click the link for a nifty visualization of how the number and size of dams has grown over time).
I’ll leave aside for a moment the fact that, among other flaws, the region’s dams are bad for salmon, and may cause substantial greenhouse gas emissions when vegetation is submerged—and admit that, yes, without hydropower the Northwest would be burning a lot more fossil fuels, particularly coal, to generate its electricity.
That said, the Northwest states are becoming increasingly dependent on coal and natural gas to produce electricity. The dams’ power output fluctuates with the weather each year, but has remained roughly constant since the mid-1970s. But the region’s population grew by two-thirds over the same period—which means that, person for person, the amount of hydropower generated per resident has been declining steadily since the 1970s. See the pink line, here:
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Since the mid-1980s, it’s only been in the wettest years that the Northwest’s dams produce as much electricity as we use. The shortfall is made up with fossil fuels—including coal-fired power plants that operate in Nevada, Wyoming, and other far-flung locales.
Now, per capita electricity consumption has also tapered off in the last few years (see the blue line above). The biggest reason is that high electricity prices in 2001—the year of the California’s rolling electricity blackouts—forced the closure of most of the Northwest’s power-hungry aluminum smelters (see this previous post for a picture of what that meant for Washington’s industrial electricity consumption).
Closing the smelters plugged a hole in supplies in 2001. But that trick can’t work a second time, since most of the smelters are still offline. Which means that we’re especially lucky, given this summer’s impending drought in the Northwest states—likely worse than in 2001—that California’s been having weirdly wet weather, and isn’t expecting (Sacramento Bee article, registration required) imminent hydropower shortages of its own.
Otherwise, we’d be staring down the barrel of a power crisis that could make the price spikes and roling blackouts of 2001 seem trivial.