Matching the water exported from the Delta to annual water availability reduces pressure on the Delta ecosystem.

The Measure

Water exported from the Delta will more closely match water supplies available to be exported, based on water year type and consistent with the coequal goal of protecting, restoring, and enhancing the Delta ecosystem. This will be done by improving use of water during wet years and limiting use of water during dry years.

  • Expectations

    The amount of water exported affects many other aspects relating to the health of the Delta, including salinity, invasive species, and more.

  • Performance Metrics

    • Total water exported by the SWP and the CVP during each critically dry year.
    • Total water exported by the SWP and CVP each wet year.

15 Year Rolling Average of Water Exports

This hydrograph shows the 15 year rolling average of the combined exports from State Water Project (SWP) and Central Valley Project (CVP).  A lighter line shows the actual exports for that year.

Wet Year and Critically Dry Year Exports

During wet years when there is more available water, exports should increase. During critically dry years when the ecosystem is most vulnerable exports should decrease. These graphs show exports from the Delta during wet water years and critically dry water years.

Many water suppliers in California rely on water exported from the Delta through the Central Valley Project (CVP) and State Water Project (SWP). However, reliance on the Delta means greater pressure on the Delta ecosystem for its water, and more vulnerability, both for the ecosystem and water suppliers, to the impacts of climate change and catastrophic events. Reducing reliance on the Delta is essential for achieving the coequal goals of improving the Delta’s ecosystem and providing a more reliable water supply for the state of California.

Managing Delta exports based on the amount of water available in the system can benefit the ecosystem. Specifically, exports during critically dry years have a greater chance of conflicting with the Delta’s aquatic ecosystem. During critically dry years, the Delta experiences lower inflows to support its natural communities. During wet years, Delta inflow is higher and many aquatic species are less stressed by exports. In addition to matching water exports during a wet year and critically dry year, a statistically significant overall reduction in water exports is expected to match an overall decrease in the amount of water available under changing climate and sea level rise projected for California.

The Central Valley Project (CVP) and State Water Project (SWP) are complex water systems that provide water supply, flood protection, and hydroelectric power to California. The CVP is operated by the federal government while the SWP is operated by the State of California. Central to both systems is water exported from the Sacramento-San Joaquin Delta to water suppliers across California. Water exported from the Delta is used for more than 27 million people and for irrigation of about 3 million acres of farmland. Overall, water exports from the Delta account for about 8% of the water used in the entire state (Delta Plan, p. 75).

In California, the peak of precipitation occurs near the New Year. In order to make it easier to compare water availability between years, California uses “Water Years” which run from October 1 to September 30.  The Department of Water Resources uses an index to determine if each water year fits into the category of Wet Year, Above Normal, Below Normal, Dry Year, and Critically Dry Year.  For the Sacramento Valley, the index uses a formula that accounts for the amount of runoff as well as how wet the previous year was.

Each chapter of the Delta plan includes strategies to achieve the goals of the plan. These strategies are general guidance on achieving the objective laid out in the plan and in the Delta Reform Act of 2009. Associated with these strategies are recommendations. The recommendations describe more specific and implementable actions to support the achievement of Delta Plan strategies. Strategies and recommendations may also have associated performance measures. Delta Plan performance measures track progress in achieving desired outcomes for the Delta Plan. Below are the strategies and recommendations associated with this performance measure.

Delta Plan Strategy
  • Improve Conveyance and Expand Storage

Delta Plan Recommendations
  • Promote Options for New and Improved Infrastructure Related to Water Conveyance
  • Evaluate, Design, and Implement New or Improved Conveyance or Diversion Facilities in the Delta
  • Improve or Modify Through-Delta Conveyance
  • Promote Options for New or Expanded Water Storage
  • Design, Construct and Implement New or Expanded Surface Water Storage
  • Implement New or Expanded Groundwater Storage
  • Promote Options for Operations of Storage and Conveyance Facilities
  • Operate Delta Water Management Facilities Using Adaptive Management Principles
  • Update the Bay-Delta Plan and Consider Drought
  • Operate New or Improved Conveyance and Diversion Facilities Outside of the Delta
  • Promote Water Operations Monitoring Data Management, and Data Transparency
  • Complete Surface Water Storage Studies
  • Identify Near-term Opportunities for Storage, Use, and Water Transfer Projects
  • Improve Water Transfer Procedures
Metric
  • Total water exported by the State Water Project and the Central Valley Project, during each critically dry year, through the Harvey O. Banks and C.W. Bill Jones Pumping Plants in the southern Delta. This will be evaluated following critically dry years.
  • Total water exported each wet year by the State Water Project and the Central Valley Project, through the Harvey O. Banks and C.W. Bill Jones Pumping Plants in the southern Delta. This will be evaluated following wet years.
  • Fifteen-year average total water exported annually (for all water year types) by the State Water Project and the Central Valley Project, through the Harvey O. Banks and C.W. Bill Jones Pumping Plants in the southern Delta. This will be evaluated at least every five years.
Baseline
  • Median total water exported during critically dry years by the State Water Project and the Central Valley Project, through the Harvey O. Banks and C.W. Bill Jones Pumping Plants in the southern Delta, for the years 1975–2014.
  • Median total water exported during wet years by the State Water Project and the Central Valley Project, through the Harvey O. Banks and C.W. Bill Jones Pumping Plants in the southern Delta, for the years 1975–2014.
  • Average total water exported annually (for all water year types) by the State Water Project and the Central Valley Project, through the Harvey O. Banks and C.W. Bill Jones Pumping Plants in the southern Delta, for the years 2000–2014.
Target
  • A statistically significant decrease in annual total exports during critically dry years as compared to historical deliveries for critically dry years in 1975–2014. This target is to be achieved by 2030.
  • A statistically significant increase in total exports during wet years compared to historical deliveries for wet years in 1975–2014. This target is to be achieved by 2030.
  • Fifteen-year average total exports during all year types decreases by 5 percent or more from the average historical deliveries for the years 2000–2014 (5.1 million acre-feet (MAF). This target is to be achieved by 2030.
Methods

Daily cubic feet per second were converted into million acre-feet per year.  Then 15 year rolling averages were calculated.  For aggregation by water year, Sacramento River water year was used. 

Data Source

Day flow for daily exports

CDEC for Water Year Type
 

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