Tag

rivers
15
Dec

A large pulse of water sent through the Yolo Bypass in summer 2016 boosted phytoplankton biomass and food web conditions in Cache Slough and the lower Sacramento River, a new report confirms.

 “Our goal was to improve estuarine habitat by increasing net flows through the Cache Slough Complex to enhance downstream transport of lower trophic-level resources, an important driver for fish such as the endangered Delta Smelt,” write the authors—including esteemed (and recently retired) California Department of Water Resources lead scientist Ted Sommer—in the latest issue of San Francisco Estuary and Watershed Science. The pulse occurred over three weeks in July, a time when flows in the region above Cache Slough are often negative (meaning they go “upstream”) due to agricultural diversions and low freshwater inflow. Producing the pulse, which increased downstream flows from about negative-two cubic meters per second to a peak of 15 cubic meters per second in the Toe Drain...
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20
Aug

Scientists are finding it increasingly difficult to predict how ecosystems will respond to sudden and rapid changes such as extreme droughts, wildfires, and flooding.

Writing in the June 2021 issue of San Francisco Estuary & Watershed Science, a group led by environmental economist Richard Norgaard note that due to the increasing pace of ecological change associated with a warming world, models derived using past data are less able to provide reliable predictions, particularly as extreme events create conditions outside historic reference points. This has global implications for environmental management, but the authors—many of whom have served on the Delta Independent Science Board—center their focus on the Sacramento-San Joaquin Delta. Environmental managers often speak of ecosystem resilience but the authors argue it’s just as important to apply the concept of resilience and adaptability to our human systems of policy-making and management.“Without a concerted effort, scientists, policy-makers, and managers...
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20
Aug

Loss of wetland habitat in the Delta has reduced net primary productivity by 94%, but achieving current restoration goals could restore 12% of this loss.

In a new study published in the September 2021 issue of Science of The Total Environment, researchers modeled net primary production of the Delta under historical and contemporary conditions in order to project the potential benefits of restoration. The loss of net primary productivity—the amount of energy available to pass up the food chain—associated with human modification of the Delta since the early 19th century has reduced the energy available to support biodiversity and ecosystem services. Using the San Francisco Estuary Institute’s Historical Ecology Project, which modeled the early Delta based on archival photos, maps, and texts from the early 1800s, researchers estimated the total area for five specific habitat types: open water, tidal marsh, non-tidal marsh, riparian forest/scrub, and seasonal floodplains. The...
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20
Aug

When it comes to managing Delta salinity, a new research paper suggests we treat public policy like a science experiment.

As anthropogenic factors like salt accumulation through irrigation and freshwater storage combine with drought and sea-level rise, the Delta is headed for a saltier future. The June 2021 paper, published in San Francisco Estuary and Watershed Science, integrates biological and physical sciences to draw a comprehensive picture of Delta salinity and changing freshwater inflow. Changing salinity patterns could have a profound impact on the region’s ecology, affecting how and when fish like the Delta smelt or Coho salmon spawn, and which aquatic plants survive. The paper insists that the patterns observed suggest that the future will be difficult to predict, as extreme weather events will lead to bigger fluctuations in salt levels, and recommends that management agencies encourage interdisciplinary coordination when approaching future...
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Smelt cam photo
19
Aug

Monitoring Delta smelt with an underwater camera could be safer and more effective than with a traditional trawl.

Standard smelt surveys rely on the use of boat-driven nets, which trap fish by funneling them from the wide mouth of the net to the closed end (known as the cod end). To check their catch, researchers must pull the net and its contents from the water. But this additional handling can harm and even kill the same fish that wildlife agencies are trying to save with the support of robust, long-running monitoring efforts. There may be a better way: According to a new study in the June 2021 issue of San Francisco Estuary and Watershed Science, the use of an underwater camera—the “SmeltCam,” developed about a decade ago by U.S. Geological Survey (USGS) research fish biologist Frederick Feyrer—could provide...
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photograph of beautiful tree overhangin a river
19
Aug

Modern water management practices damp down natural river patterns and produce streamside forests that “live fast and die young.”

Such practices also hasten the destruction of an important and dwindling habitat. Melissa Rohde of the State University of New York College of Environmental Science and Forestry (SUNY-ESF) and colleagues analyzed five years of high-resolution satellite and water resource data showing vegetation greenness along California rivers. Trees growing alongside the 30 percent of state rivers with natural flows decreased in greenness from the wet spring through the dry summer months, the scientists report in the Proceedings of the National Academy of Sciences, demonstrating they rely on groundwater to make it through the dry season. By contrast, woodlands along the 70% of streams receiving water from dams, wastewater treatment plants, and other human sources kept up the same vigorous levels of...
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