In the absence of a government program to contend with harmful algae blooms (HABs) in the Delta, a loose coalition of academics and environmental and community groups has been studying their spread and potential health impacts both from ground level and from the air.

In the absence of a government program to contend with harmful algae blooms (HABs) in the Delta, a loose coalition of academics and environmental and community groups has been studying their spread and potential health impacts both from ground level and from the air.

San Francisco Baykeeper has been sending up drones to monitor eight sites between Discovery Bay and downtown Stockton, as well as photo-documenting the spread and intensity of HABs from airplanes flown by Lighthawk Conservation Flying. At the same time, volunteers with Restore the Delta have been conducting water quality testing for HABs and the toxins they produce. “The airplane and drones together allow us to get a really broad geographic understanding of where these neon green HABs are occurring, says...
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Researchers are applying a novel genetic technique as part of the development of an annual estimate for the number of juvenile spring-run Chinook salmon entering the Delta.

The technique, spearheaded by geneticist Melinda Baerwald from the California Department of Water Resources, allows researchers to accurately distinguish young spring-run salmon from other runs by targeting DNA sequences specific to these fish.   In a paper published in San Francisco Estuary and Watershed Science, lead authors Baerwald and Peter A. Nelson explain some of the challenges of developing this estimate, called the spring-run juvenile production estimate. A key hurdle is differentiating spring-run fish from salmon that migrate during other...
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Groundwater pumped from subsided islands back into Delta channels through 200 or more active outfalls can be laden with excess nitrogen transported from island soils, report the authors of a new study.

The Sacramento-San Joaquin Delta contains more than 50 peat islands. Most have subsided—some as much as three meters — as a result of drainage for farming, and must maintain artificial water tables below the land surface via managed pumping. According to researchers from the University of California at Santa Cruz and the US Geological Survey, these pump stations are an underappreciated source of nutrients in nearby waters, with potentially significant implications for habitat and water quality.   To get a...
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Light and nutrients are the staples of every phytoplankton production recipe, but wind and tides in the Delta affect phytoplankton production too, say researchers.

Several projects in the lower Sacramento River and Delta have been exploring strategies for increasing the quantity and quality of food for migratory and resident fish. As part of a broader whole-ecosystem experiment that added nitrogen into the Sacramento River Deep Water Ship Channel, Leah K. Lenoch and colleagues at USGS and UC Davis looked into the channel’s hydrodynamics to explore whether the environmental conditions there hold promise for increasing the quantity of phytoplankton (the microscopic algae at the base...
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The Tunnel Plan: Thoughts a Month Later

It’s now five weeks since Governor Newsom’s Delta tunnel plan was unveiled in a Draft Environmental Impact Statement. Time enough for the main ideas to sink in; time enough for familiar players to strike their familiar positions; and time enough for some of us to burrow deep into its tables, figures, and appendices. To recap briefly: water taken from new intakes near Hood on the Sacramento River would enter a tunnel and flow 45 miles underground before being lifted again...
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Top Photo: Sailboats crossing under Delta drawbridge. Photo: Caltrans

The Grande Dames of the Delta

The moveable bridges that cross the rivers and sloughs in the Sacramento-San Joaquin Delta were built in the first half of the 20th century, and most are operated by control panels as old as the bridges themselves. A day spent touring these strong-boned grande dames on backwater levee roads or zigzagging across the Sacramento River on scenic State Route 160 is time well spent. But that’s leisure time, and for the tens of thousands of commuters who use the heavily...
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Listening to Vital Voices

Jessica Rudnick’s first love was earth science. But after discovering that people’s beliefs and behaviors were key to solving environmental problems, she fell for social science. Now, as the California Sea Grant extension specialist for the Delta, Rudnick is working to better integrate local people into plans for the region. Understanding the needs of people who live, work, and recreate in the Delta could make the difference between fixes that are rejected or embraced.  Delta planning has historically focused largely...
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Reorienting to Salmon Recovery

The days when salmon and steelhead teemed in California’s coastal watersheds faded away last century. Today, many populations of the fish are gone or dwindling, the river systems where they spawn drained by diversions or too warm for native fish to survive. Warming trends and drought are squeezing water resources tighter. Nearly all efforts to revive the state’s ailing salmonids have failed, often stalemated by political tensions, and it takes hatcheries and truck transport of juveniles to saltwater to maintain...
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Baldocchi at the end of one of the levees breached to restore tidal action at Dutch Slough. Photo: Janet Byron

Sniffing the Delta for Greenhouse Gases

Dutch Slough in Oakley, on the southern edge of the Sacramento-San Joaquin Delta, is less than a mile from where biometeorologist Dennis D. Baldocchi (above) grew up on his parents’ orchard and fished with pals in nearby Marsh Creek. In October 2021, the California Department of Water Resources breached the levees here, restoring nutrient-rich tidal flows to degraded ranchland. Early in the 20th century, Baldocchi’s father grew dry beans and sugar beets on the peat soils of the Delta’s Liberty...
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subisdence on 4 delta islands map

Asked to suggest an appropriate future for four Delta islands owned by the Metropolitan Water District, it’s difficult not to want the moon.

Why not richer rice fields, more wetlands, better boat launches, extended trails, even eco-tourism? ? A new survey for the Delta Islands Adaptation Project, funded by a Prop 1 Watershed Restoration Grant, wants the public’s opinion on the importance of 10 possible land-use objectives leading to the selection of one of the four islands for improvements. As your blinking cursor hovers over a satellite image of Bouldin, Bacon, Webb, and Holland Tracts, the survey lays out all that the experts...
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chart by Hutton

An examination of 50 years of records reveals an apparent seasonal bias in estimates of freshwater flow from the Delta to the San Francisco Estuary.

The seasonal bias suggests flows were overestimated during the summer months and underestimated during the winter. Estimates of Delta outflow use a measurement called net Delta outflow index (NDOI), which is determined by taking the amount of Delta inflow, from sources such as the Calaveras, Sacramento, and San Joaquin rivers, and subtracting Delta exports, a direct measurement, and net Delta channel depletions. A team led by TetraTech’s Paul Hutton compared NDOI estimates against measured Delta outflow at four points, as...
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diagram of fish net trawl

Fish monitoring surveys in the San Francisco Estuary net different numbers of different fish species depending upon when and how they sample.

According to a new study published in San Francisco Estuary and Watershed Science, even surveys that target the same part of the water column can come up with significantly different catches. The study’s authors analyzed decades worth of data from the California Department of Fish and Wildlife (CDFW) Fall Midwater Trawl, which spans from San Pablo Bay to the upper Delta; CDFW’s San Francisco Bay Study midwater and otter trawls, covering the South Bay to the central Delta; and the...
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field in delta with irrigation

Rain or shine, farmers in California use about the same amount of water every year, while residential water use varies considerably with precipitation.

A research team led by UC San Diego’s John Helly processed 15 years’ worth of water-use data from the state’s Department of Water Resources, reporting in the March 2022 issue of San Francisco Estuary and Watershed Science that while “the annually precipitated water supply in the Bay-Delta” varied by 30%, agricultural water use scarcely changed year to year. “The water management system maintained nearly constant agricultural water use even in periods of intense drought, with year-to-year variation of about 7%,”...
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West Coast Salmonids All Tired Out?

West Coast salmon and steelhead populations have declined steeply in the past century – a plight that biologists have primarily blamed on habitat loss. Dams, for instance, block adult fish’s access to historic spawning grounds, and juvenile survival is impacted by streamside development and water diversions. Now, it turns out, microplastic pollution may be a much bigger factor than anyone knew just several years ago. In 2019, scientists with the San Francisco Estuary Institute and the Los Angeles-based nonprofit 5...
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Will Salmon Simmer Again?

After two critically dry years that coincided with Trump-era rollbacks to environmental protections, some iconic Delta fish are closer than ever to the point of no return. Last fall, for the second year in a row, the fall midwater trawl found zero wild Delta smelt, while a coalition of environmentalists and fishermen is asking a federal court to help prevent a repeat of 2021’s near-obliteration of endangered winter-run Chinook salmon. Their lawsuit is just one of the balls to watch...
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Gone Fishing

As the weekend dawns and California slumbers, the sportfishers descend, like clockwork, on the banks and waves of the San Francisco Bay and Sacramento-San Joaquin Delta. They carry nets for herring or poles for sturgeon, heavy and light tackle, bloodworms or anchovy or any number of delectable morsels to attract the desired target. They tread industrialized East Bay shorelines and marshy Delta banks, hop aboard sporty six-pack boats for more ambitious trips or humbler craft for a leisurely solo excursion....
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Natives Who Can Rough It

Name a native fish. One that spends lots of time in the Delta. One that’s not a salmon, smelt, or sturgeon. One whose population isn’t plummeting, and in fact seems to be doing just fine. By now the list of possibilities has been shortened severely — though not exhausted. A number of native fish still ply Delta waters in stable numbers, but precisely because there are no restoration projects, monitoring programs, or conservation efforts designed to save them — or...
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Let’s Not Forget Suisun Marsh

I started sampling the fishes of Suisun Marsh in 1979 because one of my UC Davis graduate students was looking for a place to study tule perch, a live-bearing native fish. We found not only a lot of tule perch in the marsh, but also an abundance of other native fishes. Clearly, this was a good place to study species for which we had little information at that time. Two things helped with our new project. First, sampling boats could...
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Hatchery Delta Smelt Released to Wild

On a mild day between rainstorms in mid-December, wildlife biologists outfitted in rubber boots and orange lifejackets load drum after drum of precious cargo onto a small boat docked in Rio Vista, a town on the Sacramento River in the Sacramento-San Joaquin Delta. There is little fanfare but the occasion is nonetheless momentous. The shiny silver drums contain thousands of Delta smelt — finger-size imperiled fish unique to the Delta — that were raised in a conservation hatchery. Today marks...
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Sturdy Sturgeon

A 90-year-old Australian lungfish at San Francisco’s Academy of Sciences has received a lot of press lately, but there is a wild fish species living in the San Francisco Bay that has the potential to live that long or longer — or so we think. While one white sturgeon caught in the Columbia River Basin was estimated to be 104 years old, the life expectancy of white sturgeon, Acipenser transmontanus, which includes the Central Valley population endemic to the San...
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