The Sacramento-San Joaquin River Delta (Delta) supports the largest estuary on the west coast of North America, San Francisco Bay. The Delta is a highly modified ecosystem that was first affected in the 19th century by an estimated 42 million cubic meters of sediment, largely from gold mining. Since then, over 95% of the original wetlands have been filled, leveed, diked, and drained to create agricultural land. Over several decades in the 20th century the state and national governments built the largest publically operated water system in the world to supply water for urban and agricultural uses mostly in the southern, drier parts of California. Large reservoirs were constructed to capture winter-spring runoff for use later in the year, to minimize flood risk, and to prevent salinity intrusion into the Delta from the Pacific Ocean. Today, the Delta is the hub of a system that supplies water to over 25 million residents and 12,000 square kilometers of highly productive agricultural land. Because of declining populations of several native fish in the Delta and its associated watershed, water exports have been curtailed and remain unpredictable. Recent attempts to resolve water use conflicts with endangered species focused largely on single-species conservation. These failed attempts are being replaced by the California Water Fix and California EcoRestore, dual projects formerly known as the Bay Delta Conservation Plan.
These projects will restore over 12,000 hectares of tidal and non-tidal wetlands, benefiting at least 20 endangered anadromous and resident fish and terrestrial species. Once implemented, these projects would be one of the largest wetland restoration programs in western North America. The projects would also restore and stabilize water supplies for urban and agricultural uses. The most controversial action of the plan is the construction and operation of dual 56-km-long, 12 meter-diameter tunnels under the Delta and associated new screened intakes. These tunnels would convey a portion of Sacramento River flow beneath, rather than through, the Delta. It is anticipated that this action, when implemented in accordance with a variety of protective operational criteria, would help to restore a more natural flow pattern and greater variability in Delta hydrology, benefiting native species.
The projects attempt to balance water allocation against historically competing uses: Water exports and native fish. Challenges to balancing competing water needs have included: multiple and highly uncertain ecological stressors on native species; uncertain ecological needs of the native fish; wide ranging public demands on the water supply that were beyond the scope of this program; severe over-allocation of a diminishing water supply due to changing crop demands, climate change, and an exceptional drought; limited modeling tools; and a highly litigious and political environment. A draft of the Bay Delta Conservation Plan was published in late 2013 for a 7-month public review period. This important milestone reflected diverse stakeholder recognition that the status quo was untenable and would likely worsen due to declining populations of native fish and an increasingly variable and unreliable hydrologic regime. The Plan benefitted from a high degree of scientific peer review, which in particular highlighted the need to explicitly acknowledge uncertainty and rely on adaptive management to address it. Public input was also critical: The state of California modified the proposed project several times to reduce direct and indirect impacts to local communities and natural resources. The plan also illustrates the challenge in designing water infrastructure to simultaneously restore native fisheries and improve water supply, all in the face of increasingly severe climate change. The process to develop the Bay Delta Conservation Plan, and its transition to the California Water Fix and California EcoRestore, provides lessons for the restoration of other large modified estuaries around the world, as well as the challenges of large public investments in water supply infrastructure in arid environments. A recirculated draft environmental impact assessment for the California Water Fix is due to be released in the summer of 2015. A final environmental impact assessment is expected soon after. Groundbreaking is expected in 2016 on the tunnel construction and the first phases of habitat restoration.