A Wet Winter Out West Points To A Big Spring for Hydroelectric Power

One little-noticed consequence of the heavy rain and snow falling on California and other Western states this winter: A potential boom in hydroelectric power generation this spring.

Hydropower doesn’t get much attention in the U.S. these days. Unlike wind and solar power, which are growing rapidly, there hasn’t been a flurry of new-dam construction in recent years. Unlike natural gas, the supply of which has soared thanks to hydraulic fracturing and horizontal drilling, no technology revolution has transformed the hydropower industry lately. And unlike coal, which has been at the center of heated political and environmental disputes, fights involving hydropower rarely make national headlines because they tend to involve individual dams.

But dams quietly provide a significant chunk of the nation’s power. In 2015, hydropower accounted for about 6% of the nation’s electricity supply: Almost as much as all other sources of renewable power combined. What’s more, 2015 was a year of severe drought for much of the U.S. In earlier, wetter years, dams generated significantly more power.

And 2017 is shaping up to be a very good year for generating electricity from rushing water, thanks to the soaking rains that have hit the Pacific Coast this winter, and the massive snowpack piling up in the mountains from Washington State to California.

Consider: Of the nation’s roughly 80 gigawatts of hydroelectric generating capacity, about one-fourth is  in Washington state alone. Add in Oregon and California, and the fraction rises to almost one-half. So, a wet winter for the West Coast means full reservoirs and rivers swollen by melting mountain snow in the spring. And this season is turning out to be one of the wettest on record.

California, which had until recently been suffering through an extreme, multiyear drought, has been pounded by a succession of heavy storms this winter, bringing badly needed water (along with damaging floods and mudslides). The Golden State’s long-depleted reservoirs now hold about 10% more water than normal for this time of year, according to statistics from the California Department of Water Resources. The water contained in the mountain snowpack in the Sierra Nevada is at the highest level for this time of year in the National Weather Service’s satellite records, which go back to 2004. Snow levels farther north in the Cascades Range of Washington and Oregon are also quite high.

All that rain and melting snow could potentially help the nation’s hydroelectric dams set a new power generation record this spring.

But the devil is in the details. The key to a big year for hydropower is a big snowpack that melts at the right time, says Janet Lee, the executive director of the Northwest Hydroelectric Association. An early warm-up could release too much meltwater too quickly, causing power generation to fall off abruptly later. A gradual melt, by contrast, would keep rivers flowing briskly through spring, allowing dams to make maximum use of all that kinetic energy.

Another wrinkle: Hydropower can fall victim to windy weather, Lee says. During the spring melt, the West’s many wind turbines are also spinning. If high winds cause higher than expected power generation, dams have to throttle back their own output to avoid overloading the electric grid. That is an increasing worry as wind power continues to ramp up across the country. If dams have to divert more water through spillways instead of letting it spin turbines to generate power, that’s both a waste of potential energy and harmful to certain fish species.

But if the winds cooperate and the snow melts gradually, much of the West will be blessed with abundant, low-cost, emission-free electricity this spring.

Moreover, it appears that the rain and snow will continue. The National Weather Service’s long-range forecast includes above-average precipitation chances across much of Washington and Oregon through April. And California is preparing for yet another round of heavy mountain snow later this week: Good news for skiers now and, perhaps, for electric customers later.