The State of Bay-Delta Science (SBDS) is a collection of papers intended to inform science and policy audiences about the “state of the science” for topics of high management concern in the Bay-Delta system. The other two components of the Delta Science Strategy are the Delta Science Plan (a shared vision for Delta science) and Science Action Agenda (prioritized science actions for the Delta).
The first edition of SBDS was produced in 2008, providing a system-wide baseline for the state of scientific knowledge of the system and a reframing of the interaction between policy and science.
For the 2016 edition, the editorial board - Michael Healey (University of British Columbia), Michael Dettinger (US Geological Survey), and Richard Norgaard (Emeritus, UC Berkeley) - identified the most relevant science issues based on a survey of senior scientists and managers working in the Delta. The 15 peer-reviewed papers that form SBDS 2016 cover issues ranging from contaminants in the Delta to levee stability, and from Delta food webs to recent discoveries about salmon migration.
The State of Bay-Delta Science 2016 (SBDS) is a collection of papers that summarizes the scientific understanding of the Sacramento-San Joaquin Delta.
Paper topics for this edition address the most relevant scientific issues in the Delta identified by senior scientists and managers, emphasizing progress made during the past decade and building on the first SBDS edition in 2008 (Healey et al. 2008).
Challenges Facing the Sacramento-San Joaquin Delta: Complex, Chaotic, or Simply Cantankerous?
Sam Luoma, Cliff Dahm, Michael Healey, Johnnie Moore
The report details challenges facing the Bay-Delta system within the context of the physical, water supply, water quality, ecological and institutional complexity of the Delta – and how this complexity makes it impossible to address challenges individually.
The Delta’s problems are “wicked,” meaning they have “no single correct characterization and no single correct solution, only better or worse approaches to management of the situation.”
California’s water supply is over-allocated, its water management infrastructure is decaying and overtaxed, and native ecosystems and species are declining.
Current management of the Delta is unsustainable and the current drought highlights the limitations of traditional approaches that consider solutions in isolation.
Delta Smelt: Life History and Decline of a Once Abundant Species in the San Francisco Estuary
Peter Moyle, Larry Brown, John Durand, James Hobbs
We now know more about Delta smelt than any other fish in the system, but this knowledge has not prevented the species’ trajectory towards extinction.
The Delta smelt is adapted to an ecosystem that no longer exists.
There is no “smoking gun”. The proximate causes of the decline are interactions among multiple factors that have altered their habitat, making it increasingly unsuitable.
The population exhibited some resilience when in 2011 environmental conditions were good and abundance was near historic levels, but unfortunately the current drought may have eroded such resilience.
The continued decline of Delta smelt demonstrates the general failure to manage the Delta for the “co-equal goals” of maintaining the Delta as a healthy ecosystem while providing a reliable water supply for Californians.
Anadromous salmonids in the Delta: New Science 2006-2016
Russ Perry, Rebecca Buchanan, Pat Brandes, Jon Burau, Josh Israel
The contemporary Delta has been modified to such an extent that salmon populations now contend with an alien environment.
Advancements in analysis of otoliths (bones from the inner ear) have been used to provide insights about the role of the Delta in the life cycle of juvenile salmon.
Advances in monitoring have improved our understanding of salmonid life histories, but uncertainties in the technology remain.
Understanding how juvenile salmonids of different life stages and runs survive in the Delta is critical to devising restoration and management actions.
A better understanding of how different life stages use the Delta will help inform management actions to ensure that the Delta is capable of supporting the diversity of life history strategies expressed by salmonid populations.
The effects of the recent drought on salmon populations are being evaluated, but will not be fully understood until adults return to spawn; how juvenile salmonids in the Delta have been affected by drought is unknown.
Predation on Fishes in the Sacramento-San Joaquin Delta: Current Knowledge and Future Directions
Predator-prey relationships are not static entities and there is a great deal of uncertainty surrounding predation in the Delta.
Predation involves several components, which are affected by a variety of changes that have occurred in the Delta.
Most fish predators identified were invasive species, while most non-fish predators were native species, and most prey fishes consumed were invasive species.
Thirteen hot spots were identified in the Delta. Hot spots are areas where physical conditions (e.g., unnatural or reversed flow patterns, structures such as fish ladders, pipes, modified channels or impoundments) combine to make predation more likely than in unaltered habitats.
Control of invasive predatory fish is a common management strategy, but it has not had a high success rate.
The Delta as Changing Landscapes
John Wiens, Letitia Grenier, Robin Grossinger, Michael Healey
Landscapes can be viewed in multiple ways and different perspectives can lead to different perceptions of how the same landscape is structured.
The science of landscape ecology offers a perspective on management and restoration that integrates the spatial relationships of ecological processes and the functional interconnections of land and water in the Delta.
The historical ecology perspective (using the knowledge of past landscape functions) can contribute to the restoration and management of contemporary landscapes.
The concepts and tools of landscape ecology are well developed, but they need to be applied as part of an approach that enhances the effectiveness of management, conservation, and restoration. Building on this awareness in the Delta will require a greater depth of understanding of landscape structure, function, change, and scale as they apply to the Delta.
Food Webs of the Delta, Suisun Bay, and Suisun Marsh: An Update on Current Understanding and Possibilities for Management
Larry Brown, Wim Kimmerer, Louise Conrad, Sarah Lesmeister, Anke Mueller-Solger
The landscape has changed markedly from historical conditions.
The food web is not spatially static; it varies regionally and across habitat types within regions.
New research indicates that interactions between habitat-specific food webs vary across the current landscape. For example, based on early work in the south Delta, the food web associated with submerged aquatic vegetation was thought to provide little support to species of concern; however, data from other regions of the estuary suggest that this conceptual model may not apply across the entire region.
Habitat restoration has been proposed as a method of re-establishing historic food web processes to support species of concern.
The only certainty is that food webs will continue to change in response to the changes in the physical environment and new species invasions.
Climate Change and the Delta
Michael Dettinger, Jamie Anderson, Michael Anderson, Larry Brown, Daniel Cayan, Edwin Maurer
Climate change amounts to a rapidly approaching, “new” stressor in the Sacramento-San Joaquin Delta system.
The Delta’s climate is characterized by high variability, and climate change is expected to accentuate this variability, resulting in both more extreme flood risks and greater drought risks. Thus, the Delta of the future will be very different than the Della we know today.
Effects on the Delta ecosystem include sea level rise, reduced snowpack, earlier snowmelt and larger storm-driven streamflows, warmer and longer summers, warmer summer water temperatures, and water-quality changes.
These changes and their uncertainties will challenge the operations of water projects and uses throughout the Delta’s watershed and delivery areas.
Climate change will affect the ecosystem, and although the effects are difficult to predict, it is expected that native species will fare worse than invasive species.
Despite uncertainty, successful adaptation to climate change in the Delta is possible.
California’s Agricultural and Urban Water Supply Reliability and the Sacramento-San Joaquin Delta
Much of the water supplied in California for agriculture and cities is taken directly from the Sacramento-San Joaquin Delta (Delta) or indirectly from surface and groundwater diversions upstream.
The reliability of water supplied from the Delta is threatened by drought, flood, climate change, earthquakes, growing water demands, and deteriorating conditions for endangered species and native ecosystems.
Tighter accounting and modeling of water supplies in the Delta and throughout its watershed are needed as reliability diminishes.
Research in recent years has improved understanding of how management of the Delta ties together the quantity and quality of water available statewide, from the Sierra mountains and coastal streams, through the Central Valley, to the San Francisco Bay Area, and over the Tehachapi Mountains to southern California.
Recent advances in understanding flow dynamics and transport of water-quality constituents in the Sacramento-San Joaquin River Delta
David Schoellhamer, Scott Wright, Stephen Monismith, Brian Bergamaschi
Water-quality constituents, including salinity, heat, oxygen, nutrients, contaminants, organic particles, and inorganic particles, are affected by water diversions and other human manipulations of flow, and they greatly affect the quantity and quality of benthic, pelagic, and intertidal habitat in the Delta.
The Pacific Ocean, the Central Valley watershed, human intervention, the atmosphere, and internal biogeochemical processes are all drivers of flow and transport in the Delta.
The tremendous expansion of acoustic and optical instruments deployed in the Delta over the past decade has greatly improved our understanding of how tidal variability affects flow and transport.
Sediment is increasingly viewed as a diminishing resource needed to sustain pelagic habitat and tidal marsh, especially as sea level rises.
An overview of multi-dimensional models of the Sacramento-San Joaquin Delta
Michael MacWilliams, Eli Ateljevich, Stephen Monismith, Chris Enright
Over the past 15 years, the development and application of multi-dimensional hydrodynamic models in San Francisco Bay and the Sacramento-San Joaquin Delta has transformed our ability to analyze and understand the underlying physics of the system.
Multi-dimensional models have also provided significant insights into some of the fundamental biological relationships that have shaped our thinking about the system by exploring the relationship among X2, flow, fish abundance, and the low salinity zone.
Coupling multi-dimensional models with wind wave and sediment transport models, have made it possible to understand how large-scale changes to the system are likely to affect sediment dynamics, and to assess the potential effects on species that rely on turbidity for habitat.
Coupling of multi-dimensional hydrodynamic models with particle tracking models has led to advances in our thinking about residence time, the retention of food organisms in the estuary, the effect of south Delta exports on larval entrainment, and the pathways and behaviors of salmonids that travel through the Delta
Factors and Processes Affecting Delta Levee System Vulnerability
Steven Deverel, Sandra Bachand, Scott Brandenberg, Cathleen Jones, Jonathan Stewart, Paolo Zimmaro
Large-scale, state investment in levee upgrades (> $700 million since the mid-1970s) has increased conformance with applicable standards; however, accounts conflict about corresponding reductions in the number of failures.
Modeling and history suggest that projected increases in high-flow frequency associated with climate change will increase the rate of levee failures.
A reappraisal of seismic threats resulted in updated ground motion estimates for multiple faults and earthquake-occurrence frequencies.
Estimates of the consequences of future levee failure range up to multiple billions of dollars. Analysis of future risks will benefit from improved description of levee upgrades and strength as well as consideration of subsidence, the effects of climate change, and earthquake threats.
Levee habitat ecosystem benefits in this highly altered system are few. Better recognition and coordination is needed among the creation of high-value habitat, levee needs, and costs and benefits of levee improvements and breaches.
Nutrient Dynamics of the Delta: Effects on Primary Producers
Clifford Dahm, Alexander Parker, Anne Adelson, Mairgareth Christman, Brian Bergamaschi
Many contaminants in the California Bay-Delta (Bay-Delta) exceed regulatory standards, affect aquatic species, and potentially affect human health.
Contaminants occur as dynamic complex mixtures and exert effects at multiple levels of biological organization.
The role of contaminants in the decline of Bay-Delta species is difficult to accurately assess in a complex, dynamic system. However, tools and approaches are available to evaluate contaminant effects on Bay-Delta species, and separate the effects of multiple stressors.
Contaminants also pose threats to human health via consumption of fish and shellfish, drinking water, and contact recreation, in particular, mercury, cyanobacteria toxins, disinfection byproducts, pathogens, pesticides, and pharmaceuticals and personal care
Perspectives on Bay-Delta Science and Policy
Michael Healey, Michael Dettinger, Richard Norgaard
Seven perspectives derived from SBDS 2016 highlight emerging perspectives on science and management of the Delta.
The new perspectives address nutrient and contaminant concentrations in Delta waters, the failure of the Delta food web to support native species, the role of multiple stressors in driving species toward extinction, and the emerging importance of extreme events in driving change in the ecosystem and the water supply.
Scientific advances that underpin these new perspectives were made possible by new measurement and analytic tools.
Progress toward meeting conservation objectives for the Delta is hindered by a lack of long-term perspective in science and policy.
Protection and enhancement of the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place, as required by the Delta Reform Act, has also received insufficient critical study and analysis to date.
In 2016/2017, six of the SBDS authors gave presentations on recent progress and emerging science in their field during a brown bag seminar series hosted by the Delta Science Program. The full list of seminars is available here.
2016 SUMMARY FOR POLICY MAKERS
In order to distill key findings in SBDS 2016 for a policymaker audience, two members of the editorial board prepared a summary for policymakers, The Delta on Fast Forward: Thinking Beyond the Next Crisis. This summary presents seven new perspectives based on SBDS 2016, describes a suite of tools that are advancing Delta science, and suggests eight forward-thinking actions for conducting science in the Delta. The Summary is a forward-looking take on managing the Delta that pushes our collective thinking beyond the status quo.