State Board Adopts Delta Flow Criteria

August 10, 2010

The State Water Resources Control Board (State Board) on August 3, 2010, adopted Delta flow criteria pursuant to the Sacramento-San Joaquin River Delta Reform Act that was passed in late 2009.

The final flow criteria were unchanged from draft criteria that the State Board released for public comment on July 21, 2010. The final criteria appear in a Flow Report (Report) featuring both increased Delta outflow and increased inflow from the Sacramento and San Joaquin rivers, including their tributaries:

  • 75% of unimpaired Delta outflow from January through June;
  • 75% of unimpaired Sacramento River inflow from November through June; and
  • 60% of unimpaired San Joaquin River inflow from February through June

The Report does not describe the water supply impact that would occur if the Delta flow criteria were actually applied. Some estimates suggest that water diversions from the Sacramento River watershed would have to be cut by 50 percent from November through June. Such reductions would have local, regional and statewide significance. The Report also noted its inherent limitations, in that it did not examine non-flow factors affecting the Delta’s fisheries, such as pollution, predation, exotic species or habitat loss.

In adopting the Flow Report, the members of the State Board emphasized that its recommendations could not be implemented as modifications to existing water rights without further noticed hearings, including the opportunity for cross-examination, an opportunity that was unavailable in the proceedings that led to the Report. The Report will, however, serve as a planning document for the Delta Stewardship Council and for the Bay Delta Conservation Plan in considering conveyance improvements for cross-Delta water exports.

The Delta is the logistical delivery hub for the largest single source of fresh water supply in California. The State Water Project (SWP) and federal Central Valley Project (CVP) deliver fresh water through the Delta to irrigate millions of acres of farmland and for drinking by more than 25 million Californians living in two-thirds of the state’s households from the Bay Area, to the San Joaquin Valley and Central Coast, to as far south as San Diego. The Delta also supports water supplies for local in-Delta towns and farms, and major Delta tributaries are principal sources of public water supply. For example, the San Francisco Public Utility Commission’s Hetch Hetchy system on the Tuolumne River and the East Bay Municipal Utility District’s system on the Mokelumne River serve millions of Californians living in the San Francisco Bay Area.

The State Board’s Flow Report responds to SBX7-1 (SB 1), the 2009 Sacramento-San Joaquin River Delta Reform Act. With respect to Delta flow criteria, SB 1 provides:

“For the purpose of informing planning decisions for the Delta Plan and the Bay Delta Conservation Plan, the board shall, pursuant to its public trust obligations, develop new flow criteria for the Delta ecosystem necessary to protect public trust resources. In carrying out this section, the board shall review existing water quality objectives and use the best available scientific information. The flow criteria for the Delta ecosystem shall include the volume, quality, and timing of water necessary for the Delta ecosystem under different conditions.”

(Water Code § 85086(c)(1).) Under SB 1, the State Board’s final flow criteria report must be submitted to the Delta Stewardship Council within 30 days of approval.

The 191-page Report addresses a range of legal, factual and scientific issues involving water rights, administrative procedures, the current state of the Delta, and various man-made and biological changes that have occurred in the Delta since California’s development following the gold rush. The Report states that sufficient information was considered to support the need for increased flows to protect certain ecological public trust resources, but also describes significant uncertainty in establishing specific numeric Delta flow criteria. Importantly, though, the Report concludes that physical habitat modification is not an effective substitute for instream flow.

The significance of the Delta flow criteria recommendations have yet to be considered in the context of a public trust balancing, as required for management of California’s water resources. The California Supreme Court has held that the Public Trust Doctrine does not elevate in-stream ecological use of water above the development and use of public water supplies for consumption and use away from their natural sources. (See National Audubon Society v. Superior Court of Alpine County, 33 Cal.3d 419, 445-446 (1983) [rejecting “unbalanced” interpretation of Public Trust Doctrine and acknowledging that “[t]he population and economy of this state depend upon the appropriation of vast quantities of water for uses unrelated to in-stream trust values”].) Rather, the Public Trust Doctrine requires consideration of ecological trust values in connection with the ongoing development and use of water supplies for human use. (Id. at 446.)

The Report itself acknowledges that its Delta flow criteria do not reflect any balancing of ecological values with the public water supply values. Rather, the criteria address only the ecological side of the equation, based on information that could be obtained and considered during the eight- to-nine-month period since SB1’s enactment. As the members of the State Board noted in adopting the Report, it presents only a partial perspective of California’s water needs.

Within those limitations, the Report finds recent Delta flows insufficient to support native Delta fishes in today’s habitats. It states that flow modification is one of the immediate actions available, although the links between flows and fish response are often indirect and are not fully resolved. The Report compared its flow recommendations to historic Delta flows over the last 18 to 22 years, as follows:

  • Flow criteria: 75% of unimpaired Delta outflow from January through June
  • Historic: Approximately 30% in drier years to almost 100% of unimpaired flows in wetter years for Delta outflows
  • Flow criteria: 75% of unimpaired Sacramento River inflow from November through June
  • Historic: Approximately 50% on average from April through June for Sacramento River inflows
  • Flow criteria: 60% of unimpaired San Joaquin River inflow from February through June
  • Historic: Approximately 20% in drier years to almost 50% in wetter years for San Joaquin River inflows
  • The Report provides very specific flow recommendations, measured at specific times, year types and points throughout the Delta to govern Delta hydrodynamics for the protection of various Delta fisheries. It also prescribes flows, including “pulse flows” for the San Joaquin River.

However, in adopting the Report, the State Board cautioned that it does not intend the flow criteria to be interpreted as precise flow requirements for fish under current conditions, but rather as a reflection of the general timing and magnitude of flows required under the narrow circumstances analyzed in the Report.

The Report also reaches the following additional conclusions and makes further recommendations as follows:

  • Restoring environmental variability in the Delta is fundamentally inconsistent with continuing to move large volumes of water through the Delta for export. The drinking and agricultural water quality requirements of through-Delta exports, and perhaps even some current in-Delta uses, are at odds with the water quality and variability needs of desirable Delta species.
  • Positive changes in the Delta ecosystem resulting from improved flow or flow patterns will benefit humans as well as fish and wildlife.
  • Inflows should generally be provided from tributaries to the Delta watershed in proportion to their contribution to unimpaired flow unless otherwise indicated.
  • The effects of non-flow changes in the Delta ecosystem, such as nutrient composition, channelization, habitat, invasive species, and water quality, need to be addressed and integrated with flow measures.
  • The Delta ecosystem is likely to dramatically shift within 50 years due to large scale levee collapse.
  • The numeric criteria recommended in the Report are all recommendations appropriate only for the current physical system and climate; as conditions change, the flow recommendations will also need to change. Actual flows should be informed by adaptive management.
  • A strong science program and a flexible management regime are critical to improving flow criteria. The State Board should work with the Council, the Delta Science Program, the Bay Delta Conservation Plan (BDCP), the Interagency Ecological Program, and others to develop the framework for adaptive management that could be relied upon for the management and regulation of Delta flows.
  • Studies and demonstration projects for, and implementation of, floodplain restoration, improved connectivity and passage, and other habitat improvements should proceed to provide additional protection of public trust uses and potentially allow for the reduction of flows otherwise needed to protect public trust resources in the Delta.
  • The Central Valley and San Francisco Regional Water Quality Control Boards should continue developing Total Maximum Daily Loads (TMDLs) for all listed pollutants and adopting programs to implement control actions.
  • The Central Valley Regional Water Quality Control Board should require additional studies and incorporate discharge limits and other controls into permits, as appropriate, for the control of nutrients and ammonia.
  • Temperature and water supply modeling and analyses should be conducted to identify conflicting requirements to achieve both flow and cold water temperature goals.
  • Only the underlying principles for the numeric criteria and other measures are advanced as long-term recommendations.

The range of individual stakeholders will likely have a range of views on the significance of the State Board’s Delta flow criteria for achieving water supply reliability and ecosystem sustainability. Perhaps anticipating stark differences between some stakeholders, the Report admonishes that the preceding objectives cannot be accomplished without a large-scale interdisciplinary approach focused at more than just in-stream flows. According to the State Board:

“The flow criteria identified in this report highlight the need for the BDCP to develop an integrated set of solutions, to address ecosystem flow needs, including flow and non-flow measures. . . . Although flow modification is an action that can be implemented in a relatively short time in order to improve the survival of desirable species and protect public trust resources, public trust resource protection cannot be achieved solely through flows – habitat restoration also is needed. One cannot substitute for the other; both flow improvements and habitat restoration are essential to protecting public trust resources.”

The final Report should be available soon at the State Board’s website. Meanwhile, the draft flow criteria, public comments on the draft and related materials are available at:

If you have any questions or concerns, please contact the following from our office, or the attorney with whom you normally consult.

Eric Robinson or Hanspeter Walter | 916.321.4500