Keywords:fisheries, monitoring, pollutants, Sacramento–San Joaquin Delta, water quality
How Reducing Flows Harms the Ecosystems of San Francisco Bay and Coastal Waters The Bay Institute’s major new study, San Francisco Bay: The...
The Bay Institute’s major new study, San Francisco Bay: The Freshwater – Starved Estuary, documents how the ecological health of San Francisco Bay and the nearby ocean is at high risk because large-scale water diversion in the Bay’s watershed severely limits the amount of fresh water that reaches the Bay and alters the timing of that flow. Inflow to the Bay from its Central Valley watershed now averages less than half of what it would be without diversions; in some years just one-third of the runoff makes it to the Bay. The result is a nearly permanent drought for the Bay’s fish, wildlife, and their habitats. This radical alteration creates severe consequences for the Bay and marine ecosystems – and Bay Area residents pay the price.
The study shows how unsustainable diversion of the Bay’s freshwater inflow:
Dramatically cuts production of fish and shrimp that are the food source for marine mammals, like Orca Whales, and birds;
Allows pollutants to accumulate to dangerous levels and encourages blooms of toxic algae;
Reduces sediment supply to Bay Area wetlands and beaches;
Makes it easier for undesirable non-native species to successfully invade the Bay Estuary.
The San Francisco Bay Estuary is created by the mixing of fresh water from the Central Valley’s rivers with salt water from the Pacific Ocean. Dramatically reducing the inflow of fresh water generates cascading effects in the Bay’s watershed, the Bay itself, and coastal ocean waters.
The report’s major findings include:
On average, since 1975 more than half (53%) of runoff from the Central Valley watershed has been diverted, stored, or exported before it can reach the Bay – and in many years two-thirds or more of the Bay’s inflow is captured;
As a result of intensive water diversions, the Bay experiences catastrophically dry years almost half the time (only one “supercritically dry” year occurred naturally between 1975-2014, but the Bay experienced nineteen supercritical years during that period);
Numerous unrelated fish species – from sharks to salmon, from sturgeon to smelt – show strong positive correlations with Bay Inflow; many of these species are now endangered, and even commercially viable fisheries are in decline;
Predators that feed on flow-dependent fish and shrimp are feeling the pinch – for example, dwindling supplies of Central Valley Chinook salmon may restrict the recovery of the local Orca whale population;
Blooms of toxic “algae” (cyanobacteria) are becoming more frequent, and other pollutants are becoming more concentrated, as a result of reductions in freshwater flows from the Bay’s watershed;
Bay Area beaches and tidal wetlands are deprived of sediment that was once transported by high river flows.
The study reports that local businesses are likely to suffer from the Bay’s continued decline, including those related to commercial fishing and tourism. As our Bay, beaches, wetlands, and fish and wildlife populations deteriorate, the quality of life for many Bay Area residents will also be severely – and perhaps permanently – damaged.
The study identifies four important approaches to improving Bay inflows:
Update the State’s 21 year old water quality standards for the Bay Estuary to ensure adequate inflow
Require all those who divert water destined for the Bay, not just a subset, to contribute their fair share of fresh water to support benefits enjoyed by all Californians
Invest in local water supplies around the state including conservation, and recycling, that can generate millions of acre-feet of water and reduce reliance on water diverted from the Estuary and its watershed
Coordinate management of flows with wetland and beach restoration to more effectively protect shorelines
The study was prepared for the San Francisco Estuary Partnership, a coalition of resource agencies, non-profits, citizens, and scientists working to protect, restore, and enhance water quality and fish and wildlife habitat in and around the San Francisco Bay Delta Estuary, which also provided the majority of funding for the project.
The Bay Institute's primer Gone with the Flow describes in plain language how runoff flowing from the mountain watersheds ringing California’s Central Valley...
The Bay Institute's primer Gone with the Flow describes in plain language how runoff flowing from the mountain watersheds ringing California’s Central Valley provided coldwater paradises for salmon returning to their native streams; turned lowland rivers and their floodplains into a rich source of food and shelter for young fish; mingled in the Delta’s complex maze of marshes and sloughs; and created a vast expanse of brackish water habitat essential for estuarine creatures in the upper reaches of San Francisco Bay.
The primer also explains how the lack of access to most upland streams now forces migratory fish to cope with undesirable, often lethal flow conditions; how runoff in lowland rivers has been shifted from spring to summer, or even almost completely cut off in the San Joaquin basin, with disastrous consequences for the environment; how reverse flows in Delta channels kill hundreds of millions of aquatic organisms each year; and how the Bay is now in a permanent ecological drought because of the diversion of half its freshwater inflow.
This report proposes a reconciliation approach for addressing 160 years of accumulated problems and for managing the Delta’s ecosystem in the future. Reconciliation...
This report proposes a reconciliation approach for addressing 160 years of accumulated problems and for managing the Delta’s ecosystem in the future. Reconciliation ecology seeks to improve conditions for native species while recognizing that most ecosystems have been altered irrevocably by human use and will continue to be used to support human goals. Improving ecosystem conditions for native species must, therefore, happen in a context of continuing use of land and water by humans and continuing physical and biological change.
Assembly Bill (AB) 1200 (Laird, Chapter 573, Statutes of 2005) highlighted the complex Delta water issues, and directed the Department of Water Resources...
Assembly Bill (AB) 1200 (Laird, Chapter 573, Statutes of 2005) highlighted the complex Delta water issues, and directed the Department of Water Resources (DWR) and the Department of Fish and Game (DFG) to report to the Legislature and Governor on the following:
• Potential impacts of levee failures on water supplies derived from the Sacramento-San Joaquin Delta due to future subsidence, earthquakes, floods, and effects of climate change
• Options to reduce the impacts of these factors
• Options to restore salmon and other fisheries that use the Delta estuary
The State is currently involved in four major planning efforts to evaluate ecosystem and water supply issues and consider options for improvements:
1. The Delta Risk Management Strategy (DRMS) is evaluating Delta issues primarily from the perspective of the risks from levee failures and ways to reduce those risks
2. The CALFED Ecosystem Restoration Program (ERP) Conservation Strategy is identifying restoration opportunities within the Delta and Suisun Marsh ecological restoration zones based on existing elevations, soil types, habitats and natural process requirements of pelagic organisms and other native fish species
3. The Delta Vision will develop a durable vision for sustainable management of the Delta with the goal of managing the Delta over the long term to restore and maintain identified functions and values that are determined to be important to the environmental quality of the Delta and the economic and social well being of the people of the state
4. The Bay Delta Conservation Plan (BDCP) is evaluating Delta issues primarily for the goal of obtaining permits for water supply operations through a comprehensive conservation plan for the Delta designed to protect and restore at-risk species.
Since each process has only prepared initial findings at this point in time, this document reports on progress made to define the risks and options to reduce risks for the Delta as requested by the Legislature.