Ecological implications of modeled hydrodynamic changes in the upper San Francisco Estuary

San Francisco Estuary Institute (SFEI) | June 3rd, 2016

The physical and ecological environment of the upper San Francisco Estuary has been profoundly altered since the early 1800s. Recent efforts have utilized maps of the upp

The physical and ecological environment of the upper San Francisco Estuary has been profoundly altered since the early 1800s. Recent efforts have utilized maps of the upper estuary’s historical habitat types to infer associated changes in desired ecosystem processes and functions. The work presented in this memo builds on these previous efforts, but utilizes a new tool for evaluating change over time: a 3D hydrodynamic model of the pre-development estuary. This model was constructed by Resource Management Associates (RMA) using a new digital elevation model of the pre-development upper estuary generated by SFEI and UC Davis (UCD) and “natural” boundary flows calculated by the California Department of Water Resources (CDWR). Once completed and calibrated, the pre-development model was paired with a similar model of the contemporary system in order to analyze hydrodynamic changes in the upper estuary. These analyses are presented in a technical memorandum published by RMA (2015). This memorandum takes these analyses and considers the ecological implications of modeled changes (see the “Results” section). Hydrodynamic analyses include analyzing changes in tidal prism, isohaline positions, low-salinity zone habitat, channel velocity, and source water distribution. Key findings include: • (1) a decrease in temporal salinity variability: the variability in X2 position across wet and critically dry years has been reduced, which would be expected to decrease site-scale heterogeneity in tidal marsh plant communities, with potential implications for the diversity and metapopulation dynamics of marsh animals; • (2) an increase in X2 position due to changes in estuarine geometry: changes in the geometry of the upper estuary have increased the position of X2 by an average of 3.23 km, which means substantially more water is now required to maintain X2 at any one position. Impacts of geometry-driven changes in X2 on wildlife populations are hard to predict given uncertainties in the mechanisms driving correlations between X2 and species abundance, but are potentially sizeable; • (3) loss of low-velocity refugia in blind channels: in the pre-development simulations, average channel velocities are up to 520% higher in the mainstem channel than at the head of the adjacent blind channel. Since the majority of the upper estuary's blind channels have been diked and filled, loss of these habitats is expected to have significantly decreased low-velocity refugia for aquatic organisms (such as outmigrating chinook salmon) and has likely decreased the heterogeneity of aquatic habitat with respect to velocity at the landscape-scale; • (4) changes in source water distribution: preliminary model results suggest San Joaquin source water “signal” has been severely truncated, while Sacramento “signal” has been widely diffused, which could contribute to a decrease in the ability of migratory organisms (especially adult salmon) to navigate the Delta using source-water specific chemical cues (though improved model calibration in the upper reaches of the estuary is needed to draw firm conclusions).

Ecological implications of modeled hydrodynamic changes in the upper San Francisco Estuary

San Francisco Estuary Institute (SFEI) | May 2nd, 2016

Understanding how the pre-development upper San Francisco Estuary supported native wildlife is challenging because our current understanding of local wildlife ecology is

Understanding how the pre-development upper San Francisco Estuary supported native wildlife is challenging because our current understanding of local wildlife ecology is largely based on the profoundly altered modern landscape. This difficulty is compounded by the dynamic nature of the upper estuary’s aquatic habitats, which naturally experience tremendous temporal variability, largely due to the region’s Mediterranean climate. One approach to understanding how the system historically supported native wildlife is through a lens of landscape ecology (Whipple et al. 2012; SFEI-ASC 2014). This memorandum documents the first efforts to understand the landscape ecology of the upper estuary, comprising the Sacramento-San Joaquin River Delta and Suisun Bay, using a 3D hydrodynamic model of the pre-development system. By studying the pre-development landscape, we hope to gain insight into the deficiencies of the contemporary landscape and to help develop solutions for remedying these deficiencies. 

Ensuring the Public Trust

University of California, Davis (UC Davis) | July 1st, 2012

The California Supreme Court's recognition of the public trust doctrine as an integral part of California's water rights system was one of the momentous events in the h

The California Supreme Court's recognition of the public trust doctrine as an integral part of California's water rights system was one of the momentous events in the history of California (if not United States) environmental policy.' The court looked back to the foundational purposes of the public trust to hold that there are limits to the sovereign power to privatize the rights to use the waters of the state, and it looked forward to conclude that prudent development and sustainable use of California's water resources require the state to retain authority to protect the public trust for the benefit of all Californians. The court also defined the public trust as an environmental baseline that both protects the traditional interests of navigation, commerce, and fisheries and embodies the contemporary scientific and popular understanding that there are ecological limits to the diversion and use of water for consumptive purposes. The lessons of National Audubon Society v. Superior Court2 are now a commonplace of water rights law, appearing not just in administrative orders and judicial opinions, but also in standard water rights terms, policy studies, and legislation.

Environmental Baseline Archeological and Historical Resources, Total Water Management Study for the Central Valley Basin, California

U.S. Bureau of Reclamation (USBR) | January 1st, 1975

Estimating Historical California Precipitation Phase Trends Using Gridded Precipitation, Precipitation Phase, and Elevation Data

California Department of Water Resources (DWR) | July 18th, 2014

Climate change projections for California indicate reduction in the percentage of precipitation that falls as snow, and increase in the percentage that falls as rain, due

Climate change projections for California indicate reduction in the percentage of precipitation that falls as snow, and increase in the percentage that falls as rain, due to warmer temperatures in the future. Previous work has shown overall decreases in rainfall / snowfall ratios for the western US over the last 60 years. Of interest in this study is the quantification of snow/rain ratios for smaller regions, specifically in California. Estimating cumulative precipitation phase ratios for specific regions is difficult due to large differences in local precipitation. In California, the high relief of the surface topography makes such estimates particularly difficult. The low spatial resolution of suitable precipitation/snow water equivalent monitoring stations contributes to the difficulty in quantifying the trends for sub-state sized regions of interest in this study. The present exploratory study develops and describes a methodology that uses readily available research data sets to produce gridded estimates of historical rainfall as a fraction of total precipitation for areas comprising the major water-supply watersheds of California. Using this methodology, statistically significant increases in the ratio of annual liquid to total precipitation are seen for large areas in the northern part of the State and northern Sierra over the water year. No significant annual trends are seen for regions in the central and southern portions of the Sierra. Future work extending the analysis to distinct elevation ranges and seasonality would provide more refined conclusions.

Estuary News, December 2020

San Francisco Estuary Partnership (SFEP) | December 15th, 2020

Estuary News, October 2007

San Francisco Estuary Partnership (SFEP) | October 15th, 2007

Examining the Contribution of the Observed Global Warming Trend to the California Droughts of 2012/13 and 2013/14

American Meteorological Society (AMS) | September 30th, 2014

In this study, we examine the November–February California droughts of 2012/13 and 2013/14. During 2013/14, California had its warmest and third driest rainy se

In this study, we examine the November–February California droughts of 2012/13 and 2013/14. During 2013/14, California had its warmest and third driest rainy season on record (1895–2014), while the 2012/13 season registered as the 45th warmest and 38th driest (Vose et al. 2014). The 2013 January–December calendar year was the driest on record (Water CA 2014). These consecutive below-normal seasons conspired with warm temperatures to reduce California’s snowpack to the second lowest level since 1960, when recording began, with snowpack at 24% of normal (Water CA 2014). Between January 2013 and January 2014, satellite observations documented dramatic snowpack-related land cover change (NASA Earth Observatory 2014): in 2014, the Cascade, Sierra Nevada, and Coastal ranges were almost completely devoid of snow. In February and March of 2014, air temperatures were extremely warm (NOAA NCDC 2014; HPRC 2014), and U.S. Geological Survey (USGS) observations indicated extreme or moderate hydrologic drought (USGS 2014) and high levels of vegetation stress (VegDRI 2014). The state declared a drought emergency (NIDIS 2014). While it is too soon to assess the full impact of the 2012/13 and 2013/14 California droughts, they seem likely to substantially impact the state’s ability to generate hydrologic power, support agriculture, reduce the risk of forest and bush fires, and protect fragile ecosystems (Huffington Post 2014). *Chapter 4, Explaining Extreme Events of 2013 from a Climate Perspective, Bull. Amer. Meteor. Soc., 95 (9)

Extreme and persistent drought in California and Patagonia during medieval time

Nature Portfolio (Springer Nature) | June 16th, 1994

STUDIES from sites around the world1–5 have provided evidence for anomalous climate conditions persisting for several hundred years before about AD 1300. Early workers

STUDIES from sites around the world1–5 have provided evidence for anomalous climate conditions persisting for several hundred years before about AD 1300. Early workers emphasized the temperature increase that marked this period in the British Isles, coining the terms 'Mediaeval Warm Epoch' and 'Little Climatic Optimum', but many sites seem to have experienced equally important hydrological changes. Here I present a study of relict tree stumps rooted in present-day lakes, marshes and streams, which suggests that California's Sierra Nevada experienced extremely severe drought conditions for more than two centuries before ad ∼ 1112 and for more than 140 years before ad ∼ 1350. During these periods, runoff from the Sierra was significantly lower than during any of the persistent droughts that have occurred in the region over the past 140 years. I also present similar evidence from Patagonia of drought conditions coinciding with at least the first of these dry periods in California. I suggest that the droughts may have been caused by reorientation of the mid-latitude storm tracks, owing to a general contraction of the circumpolar vortices and/or a change in the position of the vortex waves. If this reorientation was caused by mediaeval warming, future natural or anthropogenically induced warming may cause a recurrence of the extreme drought conditions.

Fish and Game Commission Twenty-Second Biennial Report for the Years 1910-1912

State of California | December 31st, 1912