SFEWS Vol. 20, Issue 2 | June 2022
#ChinookSalmon #SacramentoSplittail #tidalmarsh #floodplain #openwater #drought #flood #juvenileproductionestimate #JPE #lifehistory #raceidentification #springrun #SacramentoRiver #CADelta #quantile #regressionforest #Steelhead #machinelearning #entrainmentloss #SanFrancisco #estuary #SFE #BayDelta #gillnet #gearselectivity #Drainage #waterquality #agriculturaldrainage #returnflow #diversions #Delta #island #groundwater #nitrogen #phosphorous #metals
Considerations for the Development of a Juvenile Production Estimate for Central Valley Spring-Run Chinook Salmon
Effective species management depends on accurate estimates of population size. There are, however, no estimates of annual juvenile production for Central Valley spring-run Chinook Salmon (“spring run”), a highly imperiled species in California, making it difficult to evaluate population status and effectively manage key issues such as entrainment of this species at water diversions. In recognition of this critical information gap, we initiated an effort to develop a juvenile production estimate (JPE) for spring run, defined here as an annual forecast of the number of juvenile Central Valley spring-run Chinook Salmon that enter the Sacramento–San Joaquin Delta (“Delta”) from the Sacramento Valley.
Machine Learning Forecasts to Reduce Risk of Entrainment Loss of Endangered Salmonids at Large-Scale Water Diversions in the Sacramento–San Joaquin Delta, California
Incidental entrainment of fishes at large-scale state and federal water diversion facilities in the Sacramento-San Joaquin Delta, California, can trigger protective management actions when limits imposed by environmental regulations are approached or exceeded. These actions can result in substantial economic costs, and likewise they can affect the status of vulnerable species. Here, we examine data relevant to water management actions during January–June; the period when juvenile salmonids are present in the Delta.
Gill Net Selectivity for Fifteen Fish Species of the Upper San Francisco Estuary
Gill-net size selectivity for 15 fish species occurring in the upper San Francisco Estuary was estimated from a data set compiled from multiple studies which together contained 7,096 individual fish observations from 882 gill net sets. The gill nets considered in this study closely resembled the American Fisheries Society’s recommended standardized experimental gill nets for sampling inland waters. Relationships between gill-net mesh sizes and the sizes for each fish species retained in them were estimated indirectly using generalized linear modeling and maximum likelihood.
Nutrient and Trace Element Contributions from Drained Islands in the Sacramento–San Joaquin Delta, California
Inventorying nutrient and trace element sources in the Sacramento-San Joaquin Delta (the Delta) is critical to understanding how changes—including alterations to point source inputs such as upgrades to the Sacramento Regional Wastewater Treatment Plant (SRWTP) and landscape-scale changes related to wetland restoration—may alter the Delta’s water quality. While island drains are a ubiquitous feature of the Delta, limited data exist to evaluate island drainage mass fluxes in this system. To better constrain inputs from island drains, we measured monthly discharge along with nutrient and trace element concentrations in island drainage on three Delta islands and surrounding rivers from June 2017 to September 2018.
Climate Change Impacts on San Francisco Estuary Aquatic Ecosystems: A Review ample header
In the San Francisco Estuary, signals of climate change are apparent in the long-term monitoring record. Here we synthesize current and potential future climate change effects on three main ecosystems (floodplain, tidal marsh, and open water) in the upper estuary and two representative native fishes that commonly occur in these ecosystems (anadromous Chinook Salmon, Oncorhynchus tshawytscha and estuarine resident Sacramento Splittail, Pogonichthys macrolepidotus).
Volume 8, Issue 2, 2010
To estimate and understand recent subsidence, we collected elevation and soils data on Bacon and Sherman islands in 2006 at locations of previous elevation measurements. Measured subsidence rates on Sherman Island from 1988 to 2006 averaged 1.23 cm/year (0.5 in/yr) and ranged from 0.7 to 1.7 cm/year (0.3 to 0.7 in/year). Subsidence rates on Bacon Island from 1978 to 2006 averaged 2.2 cm/year (0.9 in/yr) and ranged from 1.5 to 3.7 cm/year (0.6 to 1.5 in/yr). Changing land-management practices and decreasing soil organic matter content have resulted in decreasing subsidence rates. On Sherman Island, rates from 1988 to 2006 were about 35% of 1910 to 1988 rates. For Bacon Island, rates from 1978 to 2006 were about 40% less than the 1926-1958 rates. To help understand causes and estimate future subsidence, we developed a subsidence model, SUBCALC, that simulates oxidation and carbon losses, consolidation, wind erosion, and burning and changing soil organic matter content. SUBCALC results agreed well with measured land-surface elevation changes. We predicted elevation decreases from 2007 to 2050 will range from a few centimeters to over 1.3 m (4.3 ft). The largest elevation declines will occur in the central Sacramento-San Joaquin Delta. From 2007 to 2050, the most probable estimated increase in volume below sea level is 349,956,000 million cubic meters (281,300 acre-feet). Consequences of this continuing subsidence include increased drainage loads of water quality constituents of concern, seepage onto islands, and decreased arability.
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Salinity Inhabited by Age-0 Splittail (Pogonichthys macrolepidotus) as Determined by Direct Field Observation and Retrospective Analyses with Otolith Chemistry
Splittail (Pogonichthys macrolepidotus) is a fish species of special concern that is endemic to the San Francisco Estuary. It has been generally accepted that spawning and juvenile rearing occurs during spring in freshwater habitats upstream of the estuary. However, the recent discovery of a genetically distinct population of splittail in the relatively brackish Petaluma and Napa rivers has challenged this assumption. We used a combination of field observations and high resolution sampling of otolith 87Sr:86Sr ratios to identify the salinity inhabited by young age-0 splittail in the Sacramento, San Joaquin, Napa, and Petaluma rivers. Individual age-0 splittail, two to three months old, were observed in the Napa and Petaluma rivers in salinity as high as 8.5 ppt and 14.1 ppt, respectively, whereas salinity in the San Joaquin and Sacramento rivers was always <1.0 ppt. Otolith 87Sr:86Sr ratios corresponding to the first month of life suggested that individual splittail in all regions mostly inhabited freshwater, although several individuals from the Napa and Petaluma rivers inhabited brackish water up to about 10 ppt. In most instances, there was little intra-individual variability in 87Sr:86Sr signals, suggesting individuals remained within the natal salinity zone during the first month of life. The exceptions were two fish, one each from the Napa and Petaluma rivers, that appeared to move from freshwater natal to brackish rearing habitats. The apparent ability of age-0 splittail to rear in brackish water almost immediately after being born is one of the fundamental mechanisms supporting splittail production in the Napa and Petaluma rivers.
Policy and Program Analysis
California’s Sacramento-San Joaquin Delta has fragile levees subject to several trends that make them increasingly prone to failure. To assess the likely extent of Delta island flooding, this study presents an economic decision analysis approach for evaluating Delta levee upgrade and repair decisions for 34 major subsided agricultural islands that make up most of the Delta’s Primary Zone and include all subsided, non-urban islands. The decision analysis provides a quantitative framework to address several relevant questions about reasonable levee upgrade and repair investments. This initial analysis indicates that it is economically optimal not to upgrade levees on any of the 34 subsided Delta islands examined, mostly because levee upgrades are expensive and do not improve reliability much. If upgrades can improve reliability more, it becomes optimal to upgrade some levees. Our analysis also suggests that, accounting for land and asset values, it is not cost effective to repair between 18 and 23 of these islands when they fail. When property values for all islands were doubled, only four islands originally not repaired become cost effective to repair. The decision analysis provides a quantitative framework for addressing several relevant questions regarding reasonable levee upgrade and repair investments. These initial results may act as a springboard for discussion, and the decision analysis model as a working framework for islands of high priority. An inescapable conclusion of this analysis is that maintaining the current Delta landscape is unlikely to be economical from business and land use perspectives.