The Freshwater Flows data story relates the history of water management and drought in the Bay and Delta.
Marsh is a home to many key species in both the Bay and Delta. A story map guides you through a comparison of changes to Bay and Delta marshland.
The tale of Bay Area stewardship of our drinking water since 1986 is remarkable for its conservation improvements and its ongoing challenges.
This table offers a brief, simplified summary of the 80 pages of information that appear in the report. The report, in turn, is based on painstaking work to assess the status and trends of the 33 indicators of estuary health listed below by teams engaging more than 100 scientists.
Legend |
Status |
Trend: |
Improving | No Change | Deteriorating | Mixed | ||
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Conditions are excellent at most Estuary beaches most of the time. Conditions have been poor at 7% of beaches in summer, and 27% of beaches in wet weather at times during recent years.
Estuary water quality is much better than 40 years ago, but the rate of improvement has slowed. Mercury, invasive species, pesticides, and trash are still problems. Improvement has been achieved for PBDEs and copper. Many potentially harmful chemicals have yet to be assessed.
Limited consumption of most popular Estuary fish species is advised due to contamination from two legacy pollutants (mercury and PCBs). Routine monitoring in place since 1994 has shown no declines in these contaminants.
The amounts and variability of freshwater inflow to the Estuary have been substantially reduced, resulting in degradation of habitat conditions and ecological function in the Estuary.
In Suisun Bay, good quality, low salinity habitat occurs too infrequently, and for too short a time, to support flow-dependent organisms and the estuarine food web. In Delta channel habitats, net downstream flow is too low to support native fish species.
The extent of eelgrass beds in the Estuary has increased, but is highly variable year to-year. The current total acreage is significantly less than the estimated maximum potential extent.
Delta marshes have been lost and fragmented to a much greater degree than Bay marshes, despite covering a greater area historically. Restoration efforts have made a significant impact on Bay habitats, but are only just getting underway in the Delta.
The benthic community at the foundation of the food web still includes many native species, but there are now many non-native species present as well. In some places, most individual benthic organisms are non-native.
Please visit the Estuaries Portal to learn additional information about the benthic monitoring program.
The fish community differs across the Estuary with increasingly poor conditions toward the upper Estuary. Native fish abundance in the brackish and fresh upper Estuary has declined markedly during the past three decades and is in poor condition.
Harbor seal numbers in the Bay are relatively stable, but have not increased in tandem with coastal populations.
Wintering dabbling duck populations are strongly increasing across all parts of San Francisco Bay. Wintering diving duck populations are strongly decreasing in Central and North Bays but remain stable in the South Bay.
Populations of dabbling ducks that breed in the Estuary are mostly decreasing across Suisun Marsh and the Delta. Less common dabblers (non-Mallards) are increasing in the Delta.
The Estuary’s population of large shorebirds is declining, especially in the South Bay. In the Central and North Bay, populations of medium and small shorebirds are stable or increasing, while in the South Bay they are on the decline.
Heron and egret nest density is increasing over the long term. Nest success, in terms of fledged chicks, is relatively stable. Subregions reveal more complex patterns.
Tidal marsh bird densities are increasing for two of three species. As restored marshes mature, they are supporting more resident marsh birds.
In the North Bay, endangered Ridgway’s rail populations have rebounded since a 2007-2009 decline. South Bay populations have stabilized at low levels after a similar decline, but not rebounded.
Most land around the Estuary available for estuarine habitats to migrate landward, and accommodate higher sea levels, has been developed. Very little of the undeveloped portion is protected.
Flood flow events are now too infrequent, too small and too short in the Estuary to support important ecological processes. Dams, levees and water diversions have cut high volume inflows and beneficial inundation of the Yolo Bypass floodplain.
The abundance of fish varies across the Upper Estuary. In the historically productive marsh and open water zones, small forage fish are declining, but in the Delta beach zone, they are increasing.
The abundance of fish varies across the Upper Estuary. In the historically productive marsh and open water zones, small forage fish are declining, but in the Delta beach zone, they are increasing.
The breeding success of Brandt’s cormorants in recent years indicates that they are finding enough food in the open waters of the Estuary to feed their young, following a severe decline in success from 2009-2012.
Heron and egret brood size is relatively stable across the Bay.
In the Bay Area, urban water conservation efforts have lowered water use while population has increased. Short-term water use reductions in response to the drought have exceeded State-mandated targets but they may be short-lived.
The Bay Area currently offsets 5% of its urban water demand with recycled water, but lags behind other urban centers in the state.
In recent years, public access to Bay and Delta trail systems has steadily increased.
For the report indicators, our science contributors developed individual technical appendices, which you will find embedded in the above “Summary of Estuary Health 2015.” If it interests you, we also feature a comprehensive collection of all appendices.