Uncertain future ahead for California hydropower

Climate change could make it harder for California to address climate change.

Greenhouse gas emissions covered under the state's cap-and-trade program fell last year thanks in part to a wet winter, which increased the amount of carbon-free hydropower on the electric grid.

But state leaders cannot rely on hydro generation as a stable alternative to fossil fuels, according to a new study that predicts climate change will decreases the amount of rainfall in the state.

Precipitation in California may drop by as much as 15pc within the next 20-30 years, according to the study from the Lawrence Livermore National Laboratory published yesterday.

The researchers found that melting sea ice in the Arctic may trigger atmospheric "ridges" in the northern Pacific Ocean that divert wet winter air north into Alaska and Canada and away from California. They conclude that sea-ice loss of the magnitude expected in the next decades could "substantially impact" California's precipitation and "exacerbate" future droughts in the state.

California was punished for four years of drought before record amounts of precipitation in the Sierra Nevada mountains led governor Jerry Brown (D) to declare an end to the emergency this spring. The recovery began in earnest in 2016, as evidenced by year-to-year changes in California's energy mix.

Hydroelectric dams contributed 29,000GWh of electricity last year, more than doubling the 2015 total, according to the California Energy Commission. As more hydropower kicked in, the state's grid operators idled natural gas power plants, the largest source of electricity in the state and a contributor to carbon emissions. The electricity provided by natural gas dropped by 16pc last year. Hydro filled most of the gap.

That swap — hydro for natural gas — factored in to a 5pc drop last year in greenhouse gas (GHG) emissions covered by California's cap-and-trade market.

Hydropower should feature prominently in California's energy portfolio in 2017 after late winter snows and spring rains further built up the water supply. If hydropower continues to supplant large amounts of natural gas this year, the state will likely stay on track to cut GHGs to 1990 levels by 2020.

But California will have a difficult time meeting ambitious climate goals set for 2030 and 2050 if natural gas plants must once again step in to replace lost hydropower. Other renewables, like wind and solar, would need to ramp up.

"It is not an insignificant loss," Arne Olson, a partner at the consulting firm Energy and Environmental Economics, said of hydropower. "But it is certainly feasible to replace it with wind and solar, and I think that would be the preferred direction that California would go with respect to the energy, as compared to natural gas."

The state has mandated that 50pc of electricity come from renewable sources by 2030. Lawmakers will consider a bill next year that would require a 100pc clean energy grid by 2045.

John Andrew, executive manager for climate change at the California Department of Water Resources, said he hesitates to put too much weight on any one study and that it is probably too early to count hydropower out.

"Precipitation, especially for California, has been this real wild card," he said.

Andrew said other models point to drier conditions in southern California but more rain and snow in the northern part of the state, where most of the state's large dams are located.

But if the Livermore study's models prove accurate, California will face additional challenges beyond the electricity sector.

Dry weather deprives dams of the fuel they need to operate, but it also leads to bigger, more intense wildfires that are capable of releasing millions of tons of carbon into the atmosphere.

Perhaps not surprisingly, Brown has said that rethinking wildfire management and passing clean energy legislation are top priorities for his remaining time in office.

Despite years of planning and multiple policies to limit the impacts from climate change, California may still find that Mother Nature, made more fearsome and unpredictable by human activity, wins out.

California average precipitation inches

California energy mix, 2016