Local reservoirs are proactively releasing water at higher rates than usual in anticipation of increased inflows from heavy winter rains and snowstorms.
The Central Sierra five station index has recorded 40.1 inches of rain since Oct. 1, the beginning of the water year.
That’s 129 percent of normal levels for March 20, according to Cory Mueller, a meteorologist with the National Weather Service.
The snowpack for the San Joaquin hydrologic region, which encompasses the northern portion of the San Joaquin Valley bordered by the Sierra Nevada on the east and coastal mountains of the Diablo Range on the west, is at 160 percent of its average with about 45 inches in snow water equivalent for this time of year, based on California Department of Water Resources data.
The measurement is based on the amount of water contained within the snowpack, or more specifically, the depth of water that would result if the snowpack melted instantaneously, according to the DWR.
Water storage at New Melones Reservoir in southeastern Calaveras County is currently at 85 percent of its 2.4 million acre-feet capacity – 35 percent higher than its 15-year average for March, according to Todd Plain, a spokesman for the Bureau of Reclamation, the agency that oversees the reservoir.
Although the dam’s emergency spillway has never been tested, Plain said the bureau has been proactively releasing water in anticipation of snowpack runoff.
“This is an above-normal year at New Melones,” Plain said. “New Melones is currently encroached and with this year's large snow pack, releases down the river are made for flood control. Our goal is to make high releases now to be able to make lower and safer flow releases in the summer.”
Downstream of New Melones, Goodwin Dam has been releasing just under 5,000 cubic feet per second (CFS) into the Stanislaus River, well above its 15-year average of 230 CFS for this time of year, Plain said.
Located below Tulloch Dam, Goodwin Dam diverts water to the Oakdale Irrigation District’s (OID) main canal systems.
“(Goodwin’s releases) match up with the cumulative releases coming out of New Melones so that (Lake) Tulloch maintains much the same level, within a certain amount of feet,” Plain said. “This is done so that New Melones can vary throughout the day based on hydropower needs.”
An order for March 18 through March 20 lowered releases to around 2,000 CFS temporarily to assist in the recovery effort for a drowning on the Stanislaus River near Knights Ferry, Plain clarified.
Release levels are informed by weather forecasts as they pertain to power generation, flood control and downstream demands, in addition to a number of other factors, Plain said.
Plain added that the bureau is constantly “collaborating with Tulloch Reservoir owners and operators downstream, such that flood waters have never reached the end of the New Melones emergency spillway."
The release rate at New Hogan Lake on the Calaveras River near Valley Springs is “a little higher than normal,” according to Michelle Frobose, the park manager for the lake.
New Hogan supplies irrigation and drinking water to the Calaveras County Water District and Stockton East Water District.
Frobose said the highest point in the reservoir’s watershed is about 5,000 feet, so it’s not as affected by the snowpack as other reservoirs in the county.
“We’re right in that elevation that we need to be at for this time of year regarding predictions of rainstorms,” Frobose said.
Situated on Stanislaus National Forest Land in northern Tuolumne County, New Spicer Meadow Reservoir is currently at 37 percent of its 189,000-acre feet capacity, and has room for an additional 75-vertical feet of water, Randy Bowersox, a Hydroelectric Manager with the Northern California Power Agency told the Enterprise March 18.
CCWD owns the New Spicer Meadow Dam, and its reservoir supplies water for consumptive use, irrigation, recreation, environmental purposes and power generation, Bowersox said.
The NCPA maintains the 6-megawatt hydroelectric plant at the base of the dam, in addition to up to 253 MW of electricity from the Collierville powerhouse downstream.
“The Sierra Nevada snowpack is California’s largest and most important water storage reservoir and it is in good shape, with our local snowpack around 150 percent of normal for this time of year,” Bowersox said.
Weather and additional storms between now and summer will influence when and how much water the reservoir will receive from the snowpack, but NCPA is planning for a large runoff season.
“In recognition of the snowpack and hydrology situation, we are releasing slightly more water than normal for this time of year to make sure that we have room for the snow when it decides to melt,” Bowersox said. “It is relatively rare for New Spicer Meadow reservoir to fill and spill, having only happened a handful of times over the last 30 years, but it could happen again this year depending on how much additional snow we receive in the coming weeks.”
As for reservoirs fed by the Mokelumne River, the total system storage for the East Bay Municipal District is currently 82 percent full, Nelsy Rodriguez, a public information officer for the district told the Enterprise Friday.
That system includes Lake Pardee, Camanche Reservoir and five reservoirs in the east bay.
Receiving water diverted from Pardee for flood control, Camanche is currently at 73 percent capacity.
Rodriguez said the district broke a record in February for hydroelectric power generation due to the increased inflows.
“We’re collecting a lot of water right now,” Rodriguez said. “It’s been a great wet year, exactly what we needed.”
CCWD spokesman Joel Metzger said the district’s “water supply is looking excellent this year.”
An abundance of water supply from the snowpack will not directly impact water rates, Metzger added.
Based on recent Drought Monitor numbers, the state is drought-free for the first time since 2011.
While higher precipitation rates are important in combating drought, higher evaporation rates due to climate change that are associated with warming air temperatures and lower relative humidity are also driving increased demand for water, according to Steven Sadro, a limnologist and assistant professor in the Department of Environmental Science and Policy at the University of California, Davis.
Limnologists study inland water ecosystems, including lakes, reservoirs, rivers, streams, wetlands and groundwater.
“All this precipitation is great from the standpoint of filling the reservoirs, but the reality is there’s (still) probably going to be increased demand associated with climate change” due to evaporative drought, Sadro said.
Additionally, fire risk will still remain high, even during wet years, since it’s driven, in part, as a “function of relative humidity and air temperatures,” Sadro said.
“Precipitation in the Sierra is historically highly variable, and most climate models indicate that that degree of variability is getting larger,” Sadro added.