The California Department of Water Resources last week released its annual experimental winter outlook, which anticipated mostly dry weather conditions through Sept. 30, 2014.
If the forecast holds true, some water agencies could end up having to call for conservation next summer depending on the level of dryness.
Tuolumne Utilities District, which supplies water for most residents in Tuolumne County, is closely monitoring the snow accumulation in the watershed above Pinecrest Reservoir over the next few months, said TUD engineer Glen Nunnelly.
“Stored water from both Pinecrest and Lyons (reservoirs) will easily carry us through to March or April,” he said. “We’re finding now, however, that if we repeat a very dry year like 1977, then we would need to be taking the appropriate action.”
The DWR’s forecast was prepared by researcher Klaus Wolter, of the University of Colorado’s Cooperative Institute for Research in Environmental Sciences, using predictions based on statistical models that consider global influences on California’s climate.
California experienced back-to-back dry years in 2012 and 2013, following one of the wetter years on record in 2011. Each water year begins Oct. 1 and lasts through Sept. 30.
Wolter’s outlook in November 2012 successfully predicted a dry year in 2012-13, though it was almost derailed by storms that brought near-record rainfall to the state in late November and December that year.
There’s still a chance for similar storms to materialize over the next few weeks, Wolter said, but that wouldn’t necessarily affect the prediction for the whole year.
“My forecast last year for dry conditions in water year 2013 seemed destined for failure at first, since California experienced record wet conditions in late-November/early December,” Wolter said. “However, the remainder of the season was record dry, producing an overall result of dry for the water year.”
The state’s annual water supply is determined by a “relatively small number of storms,” DWR said, and “the absence of only two or three can shift the balance between a wet and dry year.”
Nunnelly said TUD’s water system is unique because it doesn’t have a reservoir with year-to-year “carryover” storage like some others that operate in the area. The water level in Pinecrest Reservoir resets each year with snowmelt runoff after winter.
The agency is required to maintain the reservoir’s water level at or above 5,608 feet in elevation from Memorial Day to Labor Day. When water stops spilling over Pinecrest dam, the agency relies on the smaller storage at Lyons Reservoir.
If recent warmer climate patterns persist, the “end of spill” could happen earlier in the summer and require TUD to rely on the supply at Lyons for a longer period of time, Nunnelly said.
The agency could ask for relief from the water-level restriction at Pinecrest in a “critically dry year,” Nunnelly added. However, that would likely require mandatory conservation as well.
The monitoring station in the Stanislaus River Basin that TUD uses to help determine the following year’s water supply showed 1 inch of snow Wednesday, compared with 5 inches by this time last year.
Nunnelly said it was too early to panic, especially with winter storms expected to bring up to 5 inches of snow as low as Sonora and Angels Camp this weekend.
“We had early snow in 2009 that kind of melted away and started again in mid-December. We’ve also seen years in the recent past where we didn’t get much snow until mid-December,” he said.
Calaveras County Water District, which draws from Spicer Reservoir, White Pines Lake and the Mokelumne River, has enough water in storage to last through winter, though officials have been encouraging “common sense conservation” to prepare for a possible third dry year.
Most of the watersheds that feed CCWD reservoirs rely on snowpack in the High Sierra, which makes them relatively safe from another season with light rainfall, said CCWD General Manager Mitch Dion.
“At this point, I’m not sure I would be alarmed, but I would say we need to be aware,” Dion said. “The best thing to do is to continue having everyone exercise common sense conservation.”
Meanwhile, Utica Power Authority is allocated a certain amount of water under contract each year from CCWD and the Northern California Power Agency to supply Murphys and Angels Camp. UPA water managers have said in the past that the allocation is dependent on the snowpack, so another dry year would raise concerns.
The prospect of another dry year concerns agencies outside the area as well.
Gov. Jerry Brown signed an executive order in May streamlining the approval process for voluntary transfers of water and water rights, which allow farmers and growers to sell excess supplies during dry years. The DWR has also been partnering with the National Integrated Drought Information System program to provide to urban water agencies.
The department announced last month it would allocate only 5 percent of requested water deliveries to State Water Project contractors, which include 27 public agencies throughout the state that collectively serve more than 25 million residents. The lowest previous allocation in 2010 — also 5 percent — came on the heels of statewide drought between 2007 and 2009.
A drought declaration would be dependent on the potential impacts from the lack of precipitation this upcoming year, said DWR Interstate Resources Manager Jeanine Jones.
“One or two dry years normally won’t hurt most folks,” she said. “You start seeing more impacts getting into the third year, but you would have to see how it’s shaping up to make that call.”
Jones said most precipitation in the state occurs between January and March, so the DWR typically waits until spring before announcing plans based on the anticipated water supply.
The federal Bureau of Reclamation, which operates New Melones Reservoir, waits until around the same time before releasing its water outlook, according to spokesman Louis Moore.
New Melones is currently about 43 percent of its total capacity.
“One big storm could come in between now and then and this whole conversation would mean nothing,” Moore said. “That’s what we’re hoping.”