We’ve mapped all of California’s hydropower dams as part of our series on “Water and Power.”

Craig Miller

PCWA's Ralston Powerhouse on the Rubicon River in Placer County. California typically gets about 15% of its electricity from hydro facilities inside the state..

While much is uncertain about California’s warming climate, there is little doubt that it’s already changing the fundamentals of how most of us get our water. In fact, the Bureau of Reclamation has estimated that the Sierra snowpack could be reduced by half as soon as a decade from now.

And that has some far-reaching implications that could even show up on your electric bill.

“When you hear people talk about a depleted snowpack, it’s because of warmer temperatures and the snow just cannot stay in the hills,” says Robert Shibatani, a hydrologist and consultant to numerous government agencies. He says the “hydrograph” for California — the “usual” pattern of precipitation and runoff — is already changing. “There’s no question about it,” he told me in a recent interview. “That’s not an if. It’s not even a when, because I can tell you the when. It’s happening now.”

Shibatani says it’s not that we’ll get less precipitation, necessarily, but warming temperatures will mean more of it falling as rain at higher elevations. And the relatively steady runoff we’ve come to count on to fill the reservoirs and spin the turbines throughout the summer and fall will be compressed into the late winter and early spring.

“What it’s gonna mean is that we’re gonna spill more often,” says Einar Maisch, strategic planning director for the Placer County Water Agency. “And that means we’re gonna lose generation.”

Maisch says his agency is already enlarging spillways to accommodate bigger springtime rushes of water — and he’s prepared to see power generation taper off by 5-to 6 percent at his facilities, which generates more than 200 megawatts of power, purchased by PG&E.

“Water that goes over the top [during those high-pulse periods] does not go through a turbine,” he says.

At other times, there may not be enough runoff to spin the turbines reliably. We had a sneak preview of that during those three dry years in a row that we had recently. Overall, during that time hydro generation was roughly cut in half, says water analyst Juliet Christian-Smith at Oakland’s Pacific Institute. “That has a price tag and an environmental impact as well.”

Craig Miller

PG&E's Belden Powerhouse on the upper Feather River. This stretch of the Feather has so many hydro plants on it that it's become known as the "Stairway of Power."

She ran the numbers and found that as utilities were forced to switch some of the load to natural gas-fired plants to make up the difference, “The cost to electricity consumers was about $1.7 billion dollars.” That’s billion, with a “B.” And here are some more billions from the same time frame: 13 billion additional tons of carbon dioxide emissions because, well, burning natural gas emits CO2 and hydropower does not. Christian-Smith says that, “Given the impact of this drought on our energy production possibilities and the costs that we had to pay for energy, it’s important to think about what a longer and more severe drought might do.”

And there’s another rub, says PCWA’s Maisch. “Hydro is unique.” Not only is it the cheapest form of power imaginable, but it’s the most “dispatchable,” as they say, when utilities need to make quick adjustments to meet fluctuations in electrical demand.

On a tour of one of his agency’s powerhouses, near where the Rubicon River meets the MIddle Fork of the American, “Throttling the needle valves on the Ralston generator over there can change the amount of flow by 50% within 10 minutes. It gives us a tremendous ability to ramp in counter-flow to the changes in the grid.”

That’s not a trivial matter as utilities try to balance a power grid with an increasing percentage of on-again, off-again renewables, like wind and solar. PG&E’s David Moller, who heads the National Hydropower Association, said in a recent company publication that, “The operating flexibility of hydropower is essential to grid reliability and integrating intermittent renewables.” He’s calling for an expansion of hydro, pointing out that of the 80,000 dams across the country, just three percent currently have hydro installed.

But any expansion in California will be a tricky proposition given the environmental sensitivities of the state’s mountain regions. Most projects have recently gone through — or are going through — tortuous renewals of their federal licenses, which usually result in a net reduction of power generated to accommodate environmental concerns. And in California, utilities can’t count hydropower toward their renewable energy targets.

Hear Craig’s companion radio report Monday on KQED’s The California Report. We’ve mapped all of California’s hydropower dams as part of our series on “Water and Power.”

Craig Miller

In mid-January, much of the Sierra remained snowless.

Despite what felt like a late-season deluge, this will go down as a dry winter in California’s record books.

The season’s final survey of the Sierra snowpack by California water officials confirms that even heavy spring rains and fresh mountain snow as recently as last week didn’t make up for a late start to the rainy season and one of the driest Decembers on record. Today’s survey finds water content of the mountain snow at just 40% of the long-term average. That puts four out of the last five years on the dry side, though last year was a gullywhumper.

What snow is up there is melting fast. A release from the Department of Water Resources said that, “electronic readings today show that California’s drier than usual mountain snowpack is steadily melting with warming spring weather.”

Key reservoirs are still flush from last winter’s heavy snows. The current level of Lake Oroville, the biggest single supply for the State Water Project (SWP), remains above normal. According to DWR Director Mark Cowin, “Reservoir storage will mitigate the impact of dry conditions on water supply this summer, but we have to plan for the possibility of a consecutive dry year in 2013.” If that happens, there will be little or no “carryover” storage to rescue thirsty towns and farms next summer.

DWR has pegged water deliveries to the 29 agencies on the SWP at “60 percent of the slightly more than 4 million acre-feet of SWP water requested this year. The last 100% allocation was in 2006.

For local water agencies more reliant on rainfall than the Sierra snowpack to fill their coffers, things are decidedly more upbeat.

“It looks like conditions have dramatically improved over just the last month,” says Jennifer Persike at the Association of California Water Agencies, which is still doing its own tally of spring supplies. She says a cursory check of water managers in Marin, Sonoma, and Monterey Counties, among others, is encouraging. “It does look like we are in much better position going into the summer,” says Persike, but her association stands firm by its usual conservation message: “California, rain or shine, you’ve gotta conserve water.”