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Delta Subsidence in California: The sinking heart of the state

U.S. Geological Survey (USGS) | April 8th, 2000

Summary

The Sacramento-San Joaquin River Delta of California once was a great tidal freshwater marsh blanketed by peat and peaty alluvium. Beginning in the late 1800s, levees wer

The Sacramento-San Joaquin River Delta of California once was a great tidal freshwater marsh blanketed by peat and peaty alluvium. Beginning in the late 1800s, levees were built along the stream channels, and the land thus protected from flooding was drained, cleared, and planted. Although the Delta is now an exceptionally rich agricultural area (over a $500 million crop value in 1993), its unique value is as a source of freshwater for the rest of the State. It is the heart of a massive north-to-south water delivery system. Much of this water is pumped southward for use in the San Joaquin Valley and elsewhere in central and southern California. The leveed tracts and islands help to protect water-export facilities in the southern Delta from saltwater intrusion by displacing water and maintaining favorable freshwater gradients. However, ongoing subsidence behind the levees reduces levee stability and, thus, threatens to degrade water quality in the massive north-to-south water-transfer system.

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Delta Working Landscapes Program Final Report

Delta Protection Commission (DPC) | October 14th, 2013

Summary

The Delta Working Landscapes Program (Program) is a group of projects which demonstrate how farmers can integrate habitat restoration into farming practices. The objectiv

The Delta Working Landscapes Program (Program) is a group of projects which demonstrate how farmers can integrate habitat restoration into farming practices. The objectives of the Program are to improve the environmental quality of existing landscapes in the Delta; coordinate programs with local farmers; understand the social, economic, environmental and governmental policy hurdles and/or incentives to perform conservation practices; and communicate to farmers the advantages of implementing wildlife friendly agricultural practices. The Delta Protection Commission was awarded a three year grant to construct the program through the California Bay-Delta Program in 2005. Program partners included California Department of Fish and Wildlife Ecosystem Restoration Program, Hart Restoration (Hart) and Ducks Unlimited (DU). Hart established vegetative buffers along irrigation ditch banks and hedgerow grass plantings. These plantings were designed to provide habitat for wildlife, improve water quality by reducing runoff of pesticides and sediment, enhance levee stability, and retard levee erosion. DU coordinated restoration enhancement projects which included creating seasonal and permanent wetlands on marginal farmlands. These projects provide waterfowl brooding habitat, a food source, and additional habitat sites which promote healthier waterfowl flocks. These projects total 312 acres of seasonal and permanent wetlands and 6.5 miles enhanced levees and waterways. Project areas established native plant life, have been repopulated by wildlife, and filter agricultural drainage which improves water quality and enhances levee stability. Multiple species of waterfowl are using the restoration habitat for brooding and feeding as well as staying later into the season. No easements, MOUs, fee purchases, or eminent domain were used. Challenges to Working Landscapes projects include prior long term use of pesticides and herbicides which have created a hostile environment for native plants and wildlife. Additionally, some cultural practices are not conducive to habitat creation such as practices which rely on herbicides instead of tillage. Furthermore, economic costs are affiliated with physical land alterations, and in some cases permit requirements are cumbersome. Despite these challenges, successful public/private partnerships are possible. Working Landscapes projects can be expanded through better communication between policy and regulatory agencies and publicizing successful projects.

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Development of Stage-Frequency Curves in the Sacramento-San Joaquin Delta for Climate Change and Sea Level Rise

California Energy Commission (CEC) | August 27th, 2018

Summary

Future changes in hydrologic patterns and sea level rise will impact water levels in the Sacramento-San Joaquin Delta (Delta), the hub of California’s water supply sys

Future changes in hydrologic patterns and sea level rise will impact water levels in the Sacramento-San Joaquin Delta (Delta), the hub of California’s water supply system and an important ecosystem and agricultural area. An important tool for flood management is stage frequency curves which indicate how often certain water levels (or stage) occur. The Delta poses inherent complexity in the determination of stage-frequency and requires a number of considerations. One needs to account for river flows coming into the Delta, as well as the effect of tides from the Delta’s connection to the ocean through San Francisco Bay. During storms, Delta water levels are also affected by storm surge from the advancing storm fronts coming from the Pacific Ocean. Under climate change, Delta water levels will also be affected by rising sea levels and expected changes in hydrology, such as shifts in timing and amount of precipitation and runoff and changes in how much of our precipitation falls as rain or snow (referred to as climate change hydrology in this paper). With these taken into consideration, this study lays out the assumption and method used to develop stage-frequency curves in the Delta for three different conditions: current hydrology conditions, current hydrology with sea level rise, and late-century climate change hydrology with sea level rise. In addition, water surface elevation profiles along the Sacramento and San Joaquin rivers for various magnitudes of flood events were compared to the top of levee elevations. Both the stage-frequency curves and the water surface elevation profiles comparisons to top of levee elevations provide valuable information to water resources planners and were applied to inform life and flood risk analysis for the Delta in the Central Valley Flood Protection Plan 2017 Update.

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DRERIP Ecosystem Conceptual Model: Riparian vegetation

California Department of Fish and Wildlife (CDFW) | November 14th, 2008

Summary

The Sacramento-San Joaquin Delta has immense municipal, agricultural, biological and industrial importance to the economy and livelihood of California and in turn to the

The Sacramento-San Joaquin Delta has immense municipal, agricultural, biological and industrial importance to the economy and livelihood of California and in turn to the United States. Plans to improve conditions in the Delta must address both human and biological communities. The region has been altered extensively over the past 200 years from land conversion to agriculture, fluxes in sedimentation rates, levee construction, and a completely re-plumbed network of waterways and hydrology (Thompson, 1957). Remnant, native riparian and wetland plant communities are almost completely removed and there is some question of whether the natural processes that create and maintain them can be restored (Mount and Twiss, 2005). Restoration implementation will be difficult considering the extent of alteration and complexity of both the natural system and cultural setting. The scientific approach to resolve these issues needs to reflect system complexity and represent the many potential response pathways that lead from proposed alterations. Development of conceptual models to understand these potential pathways is an important first step in understanding restoration implementation (and other management actions) in light of the complexity of the natural system and existing management scheme. The CALFED program is interested in restoring the Delta ecosystem to the extent possible. Riparian Vegetation (RV2) is but one of the natural systems of interest; others include fisheries, wildlife, and other plant communities. The conceptual model presented here deals exclusively with those physical, chemical, and ecological processes relevant to riparian vegetation. Riparian vegetation is important not only for biological conservation of the plant species themselves, but also the other flora and fauna species—and the physical and ecological processes—that depend upon riparian vegetation. Although the restoration of riparian vegetation as a component of a healthy riverine landscape has cultural and economic importance, these aspects are not included in this model. The conceptual model of riparian vegetation presented here is actually a sub-model of the larger floodplain processes/habitat model (Figure 1). The RV Sub-model is general by design, and is intended to provide a framework for potential expansion or adaptation to more-refined models of individual species, habitats, and/or entire landscapes. Spatially, we focus specifically on the floodplain or land area beginning at the upper edge of the emergent vegetation zone, then moving up in elevation and inland from the water, ending when non-floodplain areas, open water, or marsh is encountered. Together, the Floodplain model and the RV Sub-model can be used to analyze various “scenarios,” ranging from potential restoration or research actions, to water management decisions, to placement of bank protection at a specific Delta levee site. In addition, to highlight key differences in conditions that occur in the Delta, we present here two specific applications of the RV Sub-model that we generalize as a being dominated by tidal processes and another dominated by more riverine processes.

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Early Reclamation and Abandonment of the Central Sacramento-San Joaquin Delta

Sacramento Historical Society | September 15th, 2006

Summary

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Earthquakes and High Water as Levee Hazards in the Sacramento-San Joaquin Delta

Delta Stewardship Council (Delta Council) | September 30th, 2016

Summary

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Effects of ferric sulfate and polyaluminum chloride coagulation enhanced treatment wetlands on Typha growth, soil and water chemistry

Science of the Total Environment (Elsevier) | January 15th, 2019

Summary

Land surface subsidence is a concern in many deltas worldwide as it contributes to water quality degradation, loss of fertile land and increased potential for levee f

Land surface subsidence is a concern in many deltas worldwide as it contributes to water quality degradation, loss of fertile land and increased potential for levee failure. As a possible solution to these concerns, on-site coagulation enhanced treatment wetlands (CETWs), coagulation water treatment followed by wetland passage serving as a settling basin, were implemented in a field-scale study located on a subsided island of the Sacramento-San Joaquin Delta in northern California under three treatments; coagulation with polyaluminum chloride (PAC), coagulation with ferric sulfate and an untreated control. Because CETWs offer a relatively novel solution for water quality improvement and subsidence reversal due to its low-infrastructure requirements and in-situ nature, effects from these systems remain uncharted and they may have adverse effects on plant biomass production that also contribute to sediment accretion. This study focuses on the effect CETWs had on the growth of Typha spp.; the dominant vegetation in the wetlands. Plant growth parameters and nutrient content were measured in conjunction with soil, pore water and surface water chemistry. Soil analysis indicated there was no intermixing of newly formed flocs and original soil material. Where there was significant deposition of floc, PAC treatment reduced phosphateconcentrations and ferric sulfate treatment increased total Fe concentrations in surrounding water compared to the control. Results indicated coagulation treatments had no negative effects on Typha leaf nutrient content, Typha growth or allometric parameters. Additionally, no signs of plant toxicity such as necrosis, wilting or chlorosis were observed in any of the treatments. Overall, this study suggests that CETWs are viable treatment option for water quality improvement and sediment accretion while having no negative impact on the growth of Typha plants.

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Envisioning Futures for the Sacramento-San Joaquin Delta

Public Policy Institute of California (PPIC) | January 25th, 2007

Summary

California’s Sacramento-San Joaquin Delta is widely perceived to be in crisis today: its levee system is fragile, many of its native species are declining rapidly, and

California’s Sacramento-San Joaquin Delta is widely perceived to be in crisis today: its levee system is fragile, many of its native species are declining rapidly, and it lacks strong governing institutions to deal with its problems. In its current state, the Delta is unsustainable for almost all stakeholders. This report provides a comprehensive, scientifically up-to-date analysis and outlines several alternative management strategies for the Delta.

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