Recent storms affect water allocation
As expected the state has increased its water allocation after the recent storms. But maybe not as expected was the significant increase that was announced.
The State Department of Water Resources announced on Thursday the State Water Project will be able to increase its water supplies to 30 percent of what’s requested, well above the initial 5 percent announced on December 1.
This is a good sign for those more dependent on water from the federal Central Valley Project, including locally those in the Friant Division. The CVP is expected to announce its initial water allocation in February and normally closely aligns with what the state allocation is.
The State Water Project delivers water to 29 agencies that serves 27 million in the state. The state announced based on the amount of water captured and stored in recent weeks, 1.27 million acre-feet of water can be delivered in 2023.
The state said the allocation increase is the direct result of extreme weather in late December and nine atmospheric rivers in January that helped fill reservoirs and dramatically increase the Sierra Nevada snowpack. The SWP’S two largest reservoirs, Oroville and San Luis, have gained a combined 1.62 million acre-feet of water in storage — roughly enough to provide water to 5.6 million households for a year.
“We are pleased that we can increase the allocation now and provide more water to local water agencies,” said DWR Director Karla Nemeth. “These storms made clear the importance of our efforts to modernize our existing water infrastructure for an era of intensified drought and flood. Given these dramatic swings, these storm flows are badly needed to refill groundwater basins and support recycled water plants.”
The updated SWP delivery forecast takes into account current reservoir storage and is based on a conservative runoff forecast, the state said. It doesn’t take into account the current Sierra Nevada snowpack, which is another good sign considering the snowpack right now.
A snow survey was conducted at the beginning of January and other snow surveys will be conducted on February 1, March 1 and April 1. If the snowpack remains favorable, the state said it could further update its allocation as the water supply outlook becomes clear with the new snow survey data.
Due to colder temperatures the water runoff
locally in the Southern Sierra has actually continued to increase the snowpack. As of Thursday the snowpack had increased to 153 percent of average if it was April 1. As of January 26 the Southern Sierra’s snowpack was 260 percent of normal.
The average snow water equivalent also continued to rise as it was at 34.4 inches on Thursday. The snowpack and average snow water equivalent are two key factors in determining water allocation.
In addition to on the ground surveys, DWR will gather data from its Airborne Snow Observatory (ASO) surveys. For the second year in a row, DWR is broadening the deployment of these more sophisticated technologies, such as ASO surveys, that can collect snow measurements farther upslope of the Sierra Nevada. The data from these flights, which use LIDAR and spectrometer technology to measure snowpack across broad swaths of key watersheds, will be used by DWR for a more accurate measurement of the snowpack and to update water supply runoff forecasts.
DWR cautioned while recent storms have been impressive, two months remain in the wet season and the state could see a return to warm and dry conditions prior to April 1.
SWP pumps currently are operating at maximum capacity of 9,500 cubic feet per second. The state said had the proposed Delta Conveyance Project been in place, An additional 202,000 acre-feet of water – enough to supply more than 710,000 households for a year – could have been stored between January 1 and January 23 while staying within compliance of rules to protect endangered species.
The Sites Project Authority, which is overseeing the development of the Sites Reservoir in the Sacramento area, also reported a substantial amount of water could have been captures and stored from the recent storms had it been in place. The Sites Reservoir would be the first major storage project implemented in the state in decades.
The state traditionally receives half its rain and snow by the end of January. Starting in February, assessments will incorporate snowpack data and runoff forecasts.
The state did say additional actions that have been taken previously, such as submission of a Temporary Urgency Change Petition or installation of the West False River Emergency Drought Salinity Barrier in the Sacramento-san Joaquin Delta, are unlikely this year based on current conditions.
The lowest initial state allocation was zero percent on December 1, 2021, with limited water designated only for any unmet human health and safety needs. Last year’s final allocation was 5 percent plus unmet human health and safety needs. Four of the 29 State Water Contractors ultimately requested and received additional human health and safety water supply.
The recent storms have also improved the state’s drought status. The U.S. Drought Monitor results released on Thursday now considers all of Tulare County to be in a moderate drought.
The U.S. Drought Monitor rates the level of drought from lowest, abnormally dry, to moderate drought and severe drought to the two worst drought levels, extreme and exceptional drought. Much of Tulare County had previously been in the severe drought category.