Atmospheric rivers earlier this month allow for another boost to expected water supply for Californians and farmland
From the Department of Water Resources:
Today, the Department of Water Resources (DWR) announced that recent storms have allowed for another increase to the State Water Project (SWP) allocation forecast for 2025. The allocation has increased to 35 percent of requested water supplies, up from 20 percent in January based on increases in precipitation, snowpack, and reservoir storage. The SWP provides water to 29 public water agencies that serve 27 million Californians and 750,000 acres of farmland across the state.
The latest allocation forecast takes into account precipitation and snowpack conditions up to February 10, prior to a cold storm that brought welcome snow to the Sierra. That snowpack will be included in future water supply calculations along with any forecasted dry conditions ahead.
“California is experiencing a winter of extremes. We’ve seen predominately dry conditions broken up by very wet, short storm events. Those conditions mean we must move as much water when it’s available and as safely as possible,” said DWR Director Karla Nemeth. “Ultimately it will require new infrastructure to move and store enough water for California as dry spells last longer and wet periods become shorter and flashier.”
Projects like the proposed Sites Reservoir and Delta Conveyance Project would have been hugely beneficial if they were in place this season, allowing California to capture more water for use during the dry summer months. For example, the Delta Conveyance Project could have captured more than 700,000 acre-feet of additional storage so far this winter, which is enough to support more than 7 million people and nearly 2.5 million households. That also would have translated to approximately a 15 to 20 percent increase in the current State Water Project allocation, on top of the increase announced today.
Managing the existing system to capture as much stormwater as possible, water managers made required flood control releases from Lake Oroville in February and still were able to add 300,000 acre-feet of storage to the reservoir, bringing it up to 84 percent capacity.
Also this month, water managers took advantage of increased flexibility in new operating permits for the State Water Project to move approximately 16,000 acre-feet of additional water into San Luis Reservoir, which is now at 81 percent capacity. The pumping increase was made possible in part by the “storm flex” provisions in the State Water Project’s 2024 federal and state endangered species act permits, which allow for additional diversion of water supply when certain ecological conditions are met during storms. The action aligned with Governor Newsom’s January 31 direction to DWR to maximize diversion of excess storm flows to boost the state’s water storage.
Each year, DWR provides SWP allocation forecasts based on available water storage, projected water supply, and water demands. Allocations are updated monthly as snowpack, rainfall, and runoff information is assessed, with a final allocation typically determined in May or June. Learn more about how the State Water Project allocation process works at https://water.ca.gov/News/Blog/2025/Jan-25/Get-the-Facts-About-the-State-Water-Project-Allocation.
The allocation forecast notice to State Water Contractors and historical data on SWP allocations are available at https://water.ca.gov/programs/state-water-project/management/swp-water-contractors.
Metropolitan responds …
General Manager Deven Upadhyay: “The increased State Water Project allocation helps to buttress our preparedness for the inevitable swing back to dry conditions. Metropolitan started this year with a record amount of water in storage – 3.8 million acre-feet. Thanks to Southern California’s commitment to water efficiency, resulting in some of the lowest water demands the region has seen in decades, this increased allocation this year means Metropolitan will be able to meet demands with our imported supplies and may be able to add water to our record storage.
“Metropolitan is taking steps to manage these resources as effectively as possible – storing water in critical locations, accessible to communities when and where they need them, as well as raising revenues through innovative water resource management programs. We also continue to invest in water efficiency and local supplies, helping Southern California continue adapting to climate change.”
State Water Contractors respond …
Jennifer Pierre, General Manager: “The State Water Contractors welcome this allocation increase of State Water Project supplies for 2025 to 35%. However, operational and infrastructure restrictions in the south Delta need to continue to be addressed. While the water generated by adaptive management efforts is important and appreciated, it is too small to make a meaningful impact on the allocation.
“State and local water managers are working hard to predict and react to weather patterns that are made even less predictable by climate change. Continuous monitoring, responsive adjustments and adaptive management have improved our water supply conditions, while we also advance long-term solutions like the Delta Conveyance Project to further address operational restrictions.
“It is important, again, to underscore that while hydrology is a major driver of California’s water supply, how we respond to it is up to us. Had the Delta Conveyance Project been in place this year, an additional 700,000 acre-feet of water could have been captured, resulting in a 50-55% allocation to date. The Delta Conveyance Project is a critical climate adaptation strategy that must be advanced to modernize and restore the State Water Project’s ongoing reliability. In the meantime, we are encouraged by DWR’s continued focus on science to inform environmentally-protective opportunities for increased water deliveries.”
