Environmental

California DWR reports significant gains in snowpack

California DWR reports significant gains in snowpack
(Photo courtesy California DWR)

The California Department of Water Resources’ (DWR) third snow survey of the season at Phillips Station recorded 116.5 in of snow depth and snow water equivalent of 41.5 in, which is 177% of average for this location on March 3.

Snow water equivalent measures the amount of water contained in the snowpack and is a key component of DWR’s water supply forecast. DWR’s electronic readings from 130 sensors indicate the statewide snowpack’s snow water equivalent is 44.7 in, or 190% of average for this date.

“The recent storms combined with the January atmospheric rivers have contributed to an above-average snowpack that will help fill some of the state’s reservoirs and maximize groundwater recharge efforts. But the benefits vary by region, and the Northern Sierra, home to the state’s largest reservoir Lake Shasta, is lagging behind the rest of the Sierra,” DWR Director Karla Nemeth said. “It will also take more than one good year to begin recovery of the state’s groundwater basins.”

Although the statewide snowpack is just behind the record snow year of 1982-83, it varies considerably by region. The Southern Sierra snowpack is 209% of its April 1 average and the Central Sierra is at 175% of its April 1 average. However, the Northern Sierra, where the state’s largest surface water reservoirs are located, is at 136% of its April 1 average. With one month of the traditional wet season remaining, DWR is providing updated runoff forecasts to water managers and closely monitoring spring runoff scenarios and river flows to ensure the most water supply benefits from this year’s snowpack while balancing the need for flood control.

“The recent storms over the past week broke a month-long dry spell in a dramatic way,” said DWR’s Snow Surveys and Water Supply Forecasting Unit Manager Sean de Guzman. “We are hopeful that we will see more cold storms to add to our snowpack for the next month and help set up a long, slow melt period into spring.”

DWR’s Snow Surveys and Water Supply Forecasting Unit is using Airborne Snow Observatory surveys across 12 of California’s major snow-producing watersheds to collect data on the snowpack’s density, depth, reflectiveness and other factors down to a 3-meter resolution. These flights, which use LiDAR and imaging spectrometer technology, provide DWR with more information on water content than before, which is fed into physically based and spatially explicit models to generate accurate water supply runoff forecasts. These forecasts are used to develop the Bulletin 120 for forecasted spring run-off to determine water allocation and stream flows for the benefit of the environment.

While winter storms have helped the snowpack and reservoirs, groundwater basins are slower to recover. Many rural areas are still experiencing water supply challenges, especially communities that rely on groundwater supplies. It will take more than a single wet year for groundwater levels to substantially improve at a statewide scale.

On Feb. 13, Governor Newsom issued an Executive Order directing state agencies to review and provide recommendations on the state’s drought response actions by the end of April, including the possibility of terminating specific emergency provisions that are no longer needed, once there is greater clarity about the hydrologic conditions this year.

DWR conducts five media-oriented snow surveys at Phillips Station each winter near the first of each month. The next survey is tentatively scheduled for April 3.

DWR operates the State Water Project (SWP), which provides water to 29 public water agencies that serve 27 million Californians and also uses the water for hydropower generation. The SWP is a system of 32 storage facilities, 21 pumping plants, four pumping-generating plants, eight conventional hydroelectric plants and about 700 miles of canals and pipelines. Among these generating plants is the 762 MW Hyatt Powerplant at the foot of Oroville Dam.