With California's water resources facing ever increasing demands, state and federal agencies are bringing a new level of attention to the West's largest estuary. As part of this effort, EPA has reviewed its water quality programs to gauge their success and identify actions needed to accelerate restoration of water quality.

EPA's review, which was triggered by the plummeting numbers of salmon and other fish species over the last 10 years, has shown that state and federal programs under the Clean Water Act have not stemmed the decline of the estuary's aquatic resources. One species, the Delta smelt, had declined to such low levels in 2010 that fishery scientists feared it could become extinct at any time.

EPA published an advance notice of proposed rulemaking (ANPR) on February 10, 2011 asking the public to consider broadly whether EPA should be taking new or different actions under its programs to address recent significant declines in multiple aquatic species in the Bay Delta Estuary. Public comments in response to the ANPR generally support protection of aquatic resources, although opinions diverge about which stressors are the most harmful and how best to restore and protect aquatic habitat.

Seven stressors affecting fish were considered in EPA's review: ammonia, selenium, pesticides, emerging contaminants, declining estuarine habitat, fragmented migratory corridors for fish, and wetlands loss.

In August 2012, EPA published a Bay Delta Action Plan highlighting the following priority activities to work on in partnership with California water quality agencies:

• Strengthen estuarine habitat protection standards
• Advance regional water quality monitoring and assessment programs
• Accelerate water quality restoration through Total Maximum Daily Loads
• Strengthen selenium water quality criteria
• Prevent pesticide pollution
• Restore aquatic habitats while managing methylmercury
• Support the Bay Delta Conservation Plan

Collectively, these activities will contribute to the restoration of the Bay Delta Estuary. Even if they are all successfully implemented, however, they are not sufficient to resolve the multifaceted problems that have stressed the ecosystem to the point of collapse. Any solution to the complex ecological problems of the Bay Delta Estuary must be multi-faceted, including providing sufficient flows, physical habitat which is sufficiently large, connected, diverse, and self-sustaining, as well as a reduction of many types of stressors, such as contaminants, invasive species, and predation.