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According to a new study by the Delta Stewardship Council, global warming could present the largest future threat to the Delta. 


For the better part of the last two centuries, the Sacramento-San Joaquin Delta has been modified in any number of ways to meet the demands of Californians.

But a new wide-ranging study looks at what might be the most serious Delta threat that doesn’t come in the form of an excavator – global warming.

“Delta Adapts: Creating a Climate Resistant Future” was released by the Delta Stewardship Council (DSC) with an overarching goal of building climate resilience in the Delta by improving the understanding of the region’s vulnerabilities to worldwide climate change. The DSC is seeking public comments on the report. Comments will be accepted until March 16.

“We recognized that we needed to study the climate change effects on the Delta specifically,” said Harriet Ross, assistant planning director for the DSC. “There have been a lot of studies that have been done regarding climate change on a particular asset or resource or a particular part of the Delta, but never comprehensively included the entire legal Delta and Suisun Marsh. This is the first climate change study that covers this large study area. We’re looking at it more holistically, regionally and comprehensively ”

The 199-page vulnerability assessment is the first of two planned phases. Work on the second phase, adaption, is expected to begin shortly and be completed in about a year. Once complete, it will detail strategies and tools that governments and other agencies can use to help communities and ecosystems thrive in the face of climate change, while protecting critical infrastructure and economic assets.

“The Delta environment is pretty important,” said Roger Mammon, an Oakley resident and secretary of Restore the Delta. “I think the study is important, and it got a lot of young people involved.”

An estimated 27 million Californians depend on the Delta for at least a portion of their drinking water. Water from the Delta is the life blood for much of the state’s $3 trillion economy including the critical agriculture sector. Given the importance of the Delta, the findings of the vulnerability assessment are concerning.

“Climate change is already altering the physical environment of the Sacramento-San Joaquin Delta and Suisun Marsh, and we will continue to experience its effects through hotter temperatures, more severe wildfires and prolonged droughts,” reads the report’s executive summary. “Over the long term, climate change in the Delta is expected to harm human health and safety, disrupt the economy, diminish water supply availability and usability, shift ecosystem function, compromise sensitive habitats, and increase the challenges of providing basic services. Many of these impacts will disproportionately affect vulnerable communities.”

Among the report’s key findings are that flooding will continue to worsen. By 2050, 10% of the Delta’s population and 33% of Delta land will be exposed to flooding from a 100-year flood event, which is a severe type of flood that has a 1% chance of occurring in any given year.

By 2085, significant flood exposure will increase to 21% of Delta residents and 68% of Delta land. Additionally, the report finds that Delta water exports will be less reliable as dry years become drier, wet years become wetter and years with average rainfall become less frequent.

Noting the report’s finding, Kathryn Phillips, director of Sierra Club California, questioned the logic of the $15.9 billion Delta Conveyance Project that proposes the construction of a tunnel through the Delta to improve the reliability of water delivery to the Central Valley and Southern California.

“The report notes that climate change will significantly reduce river flows off the Sierra snowpack and into the Delta,” wrote Phillips. “In other words – our words – there won’t be water to capture upstream of the Delta to send elsewhere in a climate changed world. Better to invest in local and regional projects to reduce, conserve and recycle.”

The DSC also noted that there appears to be an inherent social inequity in the effects of climate change in the Delta. Residents who lack a vehicle will have trouble evacuating in the event of a major flood, while extreme heat days will disproportionately affect people who work outdoors, older adults, people with chronic illness and those experiencing homelessness.

“Climate change does not affect everyone equally,” Ross said. “People with resources are able to adapt to climate change, while people without resources or with limited resources can’t adapt as well.”

Public workshops to discuss the planning for the adaptation phase of Delta Adapts are planned for Feb. 25. and March 1.

“Climate change is here, and it’s happening,” Ross said. “We’re going to have to understand exactly how those impacts are going to play out in our communities. We all have a part in addressing how we respond to those impacts. That’s our call to action, to get folks involved in our process. Climate change is happening, no matter what. It’s going to take everyone at the federal, state and local government, as well as the general public, to pitch in together and come up with a strategy that works.”

The Delta Adapts report can be found at Comments can be emailed to the DSC at For more information on the Delta Stewardship Council, visit Information on Restore the Delta can be found at