Delta Study Predicts Stronger Floods and Less Water Supply

Delta Study Predicts Stronger Floods and Less Water Supply

Though most don’t realize it, practically all Californians are linked to the Bay-Delta region via its triple function as a source of drinking water for some 27 million Californians, a critical water provider for the Golden State’s hefty agricultural industry, and a rich and unique ecosystem. But for those who live in the legal Delta zone – some 630,000 people – the braided weave of the Sacramento and San Joaquin Rivers and their maze of associated wetlands and levees provides...
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Dutch Slough Laboratory

For a hawk’s-eye view of one of the Estuary’s most ambitious restoration efforts, visit the Dutch Slough Tidal Marsh Habitat Restoration Project’s YouTube channel. Drone-shot footage shows what the Department of Water Resources has been doing on 1,200 acres of former wetland, converted to pasture and subsided up to 15 feet, in the West Delta between Big Break and Jersey Island. After moving millions of cubic yards of soil to elevate the marsh plain, a team of engineers, scientists, and...
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As agencies wrangle over how best to protect the Delta’s dwindling native fish species, researchers want to see more consideration to the needs of the estuary’s birds.

 “If we want to restore the ecology of the Delta, we can’t just be looking in the water,” says Kristen E. Dybala of Point Blue Conservation Science. In a paper published in San Francisco Estuary and Watershed Science, Dybala and two co-authors make the case that “birds and their habitat needs are often not addressed in science syntheses, conservation planning, and large-scale restoration initiatives in the Delta.” While some birds use the same sloughs and channels that support such high-profile...
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Filling significant recently identified gaps in monitoring spring-run Chinook is critical to protecting these threatened Central Valley salmon.

“There’s no way we can manage them for recovery if we don’t understand the biological processes that govern their dynamics through time and space,” says UC Santa Cruz/NOAA salmon expert Flora Cordoleani, lead author of a study reported in the December 2020 issue of San Francisco Estuary and Watershed Science. Cordoleani and colleagues identified the monitoring gaps while building a model of the spring-run Chinook life cycle. The model accounts for three self-sustaining populations of these at-risk fish, assessing survival...
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Current estimates of young salmon lost to the south Delta pumps are based on a smattering of studies from the 1970s and should be updated, according to a new analysis.

“They don’t represent current operations,” says Ukiah-based consultant Andrew Jahn, lead author of the analysis reported in the September 2020 issue of San Francisco Estuary and Watershed Science. Current operations at the State Water Project (SWP) and the Central Valley Project (CVP) can reverse flows in the Old and Middle rivers, diverting salmon on their way to the ocean towards the projects. Existing salmon loss estimates also fail to account for a likely Old River hotspot for predators, drawn to the...
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Science in Short ~ Podcast

David Ayers: How Fish Interact with Wetlands Topography  In this podcast, Estuary News reporter Alastair Bland and UC Davis PhD student and fish researcher David Ayers discuss the Sacramento-San Joaquin Delta, its fish, its marshlands, its flows, and its future. Ayers explains the focus of his research, which seeks to reveal how underwater topography in the wetlands fringing the estuary affects interactions between predators and small fish. While restoration projects often focus on adding more water to this ecosystem and...
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Londons Roam and Feast on the Bay circa 1910

Jack London usually sailed west whenever he left the Oakland Municipal Wharf, but on December 18, 1913, he headed east — because he could. Although the canal connecting the Oakland Estuary to San Leandro Bay had been completed in 1902, it wasn’t until the U.S. Army Corps of Engineers widened and deepened the canal in 1913 that it became navigable. Aboard the Roamer, a 30-foot yawl London bought used in 1910, Jack and his wife, Charmian, approached the Park Street...
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The Delta’s Blooming Problem

Bright-green blotches of algae have been popping up all over the Delta since early summer, from Discovery Bay to the Stockton waterfront, befouling the air and poisoning the water with toxins that can sicken or even kill humans and animals. Veteran Delta watchers believe that this year’s harmful algal blooms may be the worst ever, and worry that some features of Governor Gavin Newsom’s recently released Water Resilience Portfolio for California will aggravate the problem. “We don’t have enough data...
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wetland landscape photo

Better scientific preparation could help Delta water and environmental managers respond to droughts more effectively.

That’s one key takeaway from a review of environmental management and the use of science during the 2012-2016 drought commissioned by the Delta Science Program and published in the June 2020 issue of San Francisco Estuary and Watershed Science. “There are lots of mysteries about how to manage water to benefit species, agriculture, upstream and downstream users. I think science is going to be the best solution,” says lead author John Durand of UC Davis’ Center for Watershed Science. Durand...
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More than half the water diverted from Central Valley rivers is used to irrigate cattle-feed crops, implicating beef and dairy as top drivers of recent fish declines.

Recent findings, published in Nature Sustainability in March, strengthen the environmental arguments for going vegan while rewriting the familiar narrative that almonds and other high-value tree crops are the top hogs of Central Valley water resources. The study’s authors, led by Brian Richter of Virginia-based Sustainable Waters, focused on the arid West and found that irrigated crops like alfalfa and hay, more than any others, are drying out rivers. The reduced flows are pushing dozens of fish species toward extinction....
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Should the striped bass be a suspect in the decline of the Delta smelt?

Writing in the March issue of San Francisco Estuary and Watershed Science, US Fish and Wildlife Service biologists Matt Nobriga and Will Smith suggest that the smelt’s baseline might have shifted long before anyone was paying attention, and striped bass predation may have constrained its numbers before recent water diversions and food web changes added their effects. The smelt’s historic abundance is unknown; systematic surveys didn’t begin until 1959. But it’s thought to have evolved its boom-and-bust life history in...
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Sinking Islands Capture Carbon Credits

By Emily Underwood As sea levels rise and land in the Delta sinks, agencies and landowners are recognizing that levees alone will not protect critical fresh water supplies and infrastructure. Encouraged by a recently vetted new method for calculating carbon offsets from wetlands, a flurry of new climate adaptation projects on publicly owned islands strewn along the central Delta corridor aim to defend against sea-level rise, restore habitat, and reduce greenhouse gas emissions. Until recently, the prospect of selling carbon...
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Carbon Goes Deep

By Aleta George Many Yolo County farmers and ranchers are keenly aware of climate shifts and actively involved in GHG reduction strategies. Scott and Karen Stone run Yolo Land & Cattle, a 7,500-acre ranch that lies partly in the Blue Ridge Berryessa Natural Area. The Stones have planted riparian areas and hedgerows for carbon sequestration, use solar water pumps to reduce GHGs, and manage a 400-acre conservation easement for Swainson’s hawk on their irrigated pastureland. In the Capay Valley, Fully...
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Kinky Fish Spines Linked to Selenium

By Joe Eaton Scientists with the U.S. Geological Survey and the National Oceanic and Atmospheric Administration are using new tools to track selenium, with the Sacramento splittail, a California-endemic fish, as an indicator species. Robin Stewart, lead author of a new paper on splittail and selenium, is one of the region’s most seasoned current experts on bioaccumulation of metals in estuarine species. In some sampled splittail, selenium levels exceeded the proposed EPA protective criteria for fish ovaries. Liver levels, not...
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Bob Fujimura spent his entire career with the California Department of Fish and Wildlife.

Bob Fujimura spent his entire career with the California Department of Fish and Wildlife. From 1987 until his retirement in late 2018, Fujimura served in a variety of roles at the department—but he is likely best known for heading up its long-term monitoring of native fishes in the Bay and Delta. Beginning in the mid-2000s, he oversaw annual smelt surveys with far-reaching implications for management and conservation, including the Spring Kodiak Trawl, which determines the relative abundance and distribution of...
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Rainer Hoenicke is optimistic about the changes he saw in his five years as the Delta Stewardship Council’s Science Director.

“People are coming to the table and realizing we need to be anticipating and forecasting how to adapt,” he says. Prior to joining the Science Program, Hoenicke served for nearly a decade as deputy and executive director of the San Francisco Estuary Institute, where he managed two Boards of Directors and reorganized the Institute’s program areas. “I felt challenged to do something different,” he says of the move, “since the Delta is much more controversial territory.” In Hoenicke’s eyes, the...
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A new system for treating agricultural drainage water in the Delta could also help rebuild subsided islands.

The approach—known as a Chemically Enhanced Treatment Wetland—combines chemical treatment with natural wetland processes; researchers tested it on Twitchell Island, which features corn and rice crops, as well as wetlands. They dosed agricultural ditch water with dissolved organic material (DOM), then treated it with a coagulant to precipitate the DOM, forming flocculant. The resulting water then passed though treatment wetlands, where the flocculant settled and blended with plant detritus in the sediment. The study, reported in the September 2019 San...
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Manmade features in the Delta, including riprap-armored banks, water diversion pipes, pilings, and woody debris, may be sending juvenile native fishes into the jaws of finned invaders.

“We know from a decade of doing survival studies that migrating juvenile salmon are dropping out of the system pretty much everywhere in the Delta,” says UC Santa Cruz fisheries biologist Brendan Lehman. “Physical habitat features are potentially aggregating predators and prey in ways detrimental to salmon smolts and steelhead.” The scientists report in the December 2019 San Francisco Estuary and Watershed Science that artificial light and submerged aquatic vegetation pose the most severe and widespread risks to native fishes....
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Levels of pyrethroid insecticides spike sharply in the North Delta’s Cache Slough during winter rainstorms, rendering the water so toxic that it decimates laboratory populations of a half-inch crustacean called Hyalella azteca.

However, according to a study reported in the September 2019 San Francisco Estuary and Watershed Science, Hyalella collected in the wild from Cache Slough are resistant to pyrethroids. Genetic analysis revealed that, collectively, Hyalella in the slough have four mutations for pyrethroid resistance. They also have a fifth mutation for resistance to organophosphates and likely carbamates, two additional major classes of pesticides that are applied extensively on agricultural and urban lands. “Hyalella are special,” explains co-author Helen Poynton, a molecular...
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Researchers hope new computer models will help clarify the effects of entrainment on the population of endangered Delta smelt.

Entrainment at the South Delta pumps of the State Water Project and the Central Valley Project has been a concern for years, but disentangling its impact on the dwindling smelt population from those of other environmental and water management factors isn’t easy, and operational differences between the SWP and CVP facilities complicate analysis. Now, US Fish and Wildlife Service statistician Will Smith has developed computer models for entrainment effects on different smelt life stages, part of a larger Delta Smelt...
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