Flow Criteria for the Delta Ecosystem

How Much Water Does It Take to Restore the Bay-Delta Ecosystem?

All of us who rely on water from the Bay’s Central Valley watershed and the Delta have been living beyond our water means. The system is “over-subscribed,” with too much water diverted for off-stream uses and not enough required to remain in-stream to support the ecosystem, with catastrophic results. In 2009, the California legislature approved the Delta Reform Act (which the Rivers and Delta Program helped to draft), which among other things required the State Water Resources Control Board to identify by August 2010 the flows needed to fully protect public trust resources – the ecological values held in trust for the people of California – in the Delta, without having to consider the impacts on any specific water user. The flow criteria are intended to guide Delta planning and permitting processes, including the Bay-Delta Conservation Plan being developed by state and federal water projects exporters, the new Delta Stewardship Council’s master plan, and future water rights decisions by the Board itself.

The Bay Institute authored the environmental community’s most comprehensive and exhaustive case for improving Delta flows, submitting more than 150 pages of written exhibits in February 2010 and providing expert testimony in three days of hearings in March 2010. Our flow recommendations are based on analyses that link the abundance, distribution, diversity and productivity of public trust resources like delta smelt, longfin smelt and salmon, all strong indicators of the health of the estuary and its watershed, with the actual flows necessary to achieve viable populations of these species. Our recommendations call for greater Delta outflows to provide for positive growth conditions and beneficial distribution of resident native species, higher inflows from the Sacramento and San Joaquin Rivers to inundate floodplains and support successful migration of anadromous fishes to and from the ocean, and more strict controls on reverse flows in Delta channels to prevent hundreds of millions of eggs, larvae and fish from being destroyed, and habitat conditions from being degraded, by export pumping each year.

In August 2010, the State Water Resources Control Board adopted final public trust flow criteria. In almost every case where we weighed in, the Board used our recommendations and cited our work in developing the flows adopted. Indeed, the Board improved on the work of the Bay Institute and fishery agencies by aggregating many of the individual recommended flows into an approach that restores a more natural hydrograph by requiring a much higher percentage of unimpaired (i.e., natural) runoff to be dedicated to Delta inflows and outflows. The Board’s new flow criteria would dedicate 75% of winter-spring runoff for Delta outflow; 75% of winter-spring runoff for Sacramento River inflow to the Delta; and 60% of winter-spring runoff for San Joaquin River inflow to the Delta – a vast improvement over the 50% of runoff that currently reaches the Bay on average and the trickle that the San Joaquin River has become. The criteria would also drastically restrict reverse flows in Delta channels during the winter and spring. The Bay Institute is now working to translate these non-binding flows into new flow requirements for all who divert or export water from the Delta and its watershed, through the Board’s regulatory proceedings to set new water quality standards for the Bay-Delta (with decisions due in increments from 2012 to 2014) and in other venues.