The Department of Water Resources has released the draft State Water Project Delivery Capability Report for 2023, which provides information about the key factors affecting the operation of the State Water Project and its long-term capability to continue delivering water.
The information in the Delivery Capability Report (DCR) is used by the water agencies that receive water from the project for planning purposes and to forecast future needs for increased conservation measures, new facilities, or alternative water sources. Information in the report is also important for Groundwater Sustainability Plans, Urban Water Management Plans, Agricultural Water Management Plans, and Integrated Regional Water Management Plans.
Factors affecting State Water Project deliveries
Ongoing regulatory requirements, such as those to protect endangered species and maintain water quality in the Delta, present significant challenges to the delivery capability of both the State Water Project and the Central Valley Project. These restrictions, discussed in Section 2, contribute substantially to the challenge of accurately determining the State Water Project’s water delivery capability in any given year.
Accordingly, analyses used in the Delivery Capability Report incorporate all the current regulations governing water project operations in the Delta, such as Water Rights Decision D-1641, the 2019 biological opinions, and the Incidental Take Permit. The analyses also include existing infrastructure1F and assumptions about water use upstream in the Sacramento River and San Joaquin River watersheds.
While ongoing processes such as the Bay Delta Water Quality Control Plan update, the Voluntary Agreements, and the re-initiation of Consultation for Long-Term Operations will certainly impact water deliveries, those processes have not been finalized and are not included in the analysis.
How climate change is incorporated
The DCR update includes substantially expanded climate change analysis and planning information to evaluate the effect of climate change on delivery capability.
Climate change is increasing the variability, frequency, and magnitude of floods and droughts. Projected sea level rise will complicate efforts to manage salinity levels in the Delta, requiring additional outflow to maintain water quality objectives. The report now includes multiple scenarios of future climate conditions to help estimate the resiliency of State Water Project water supply to changes in climate. The modeling analysis is discussed in Sections 6 and 7 of the report.
However, the climate change scenarios in this report only consider existing regulations, existing infrastructure, and current project operations. DWR is conducting additional studies to assess the effects of different adaptation strategies on the State Water Project’s delivery capability; those studies will be published in 2024.
The report’s findings
The report found that under existing conditions, the State Water Project’s average annual deliveries are estimated to be 2,238,000 acre-feet, 83,000 acre-feet less than the estimate for the 2021 DCR Report. The likelihood of Article 21 deliveries has increased by 11% relative to what was presented in the 2021 DCR report.
Under hot-dry climate change scenarios with no adaptation actions taken, the estimated State Water Project deliveries are 11%-21% lower than under existing conditions. Hydrological patterns are expected to intensify, with periods of high flows exceeding the capacity of existing infrastructure to capture it, and prolonged and more intense dry spells that will challenge operations.
