CVFPP Conservation Strategy Appendix D. Vegetation Management Strategy

California Department of Water Resources (DWR) | August 17th, 2017

When the 2012 Central Valley Flood Protection Plan (2012 CVFPP) and Conservation Framework were adopted by the Central Valley Flood Protection Board (CVFPB), the CVFPB co

When the 2012 Central Valley Flood Protection Plan (2012 CVFPP) and Conservation Framework were adopted by the Central Valley Flood Protection Board (CVFPB), the CVFPB considered the levee vegetation management strategy contained in the 2012 CVFPP as interim. CVFPB Resolution No. 2012-25 directed the California Department of Water Resources (DWR) to further develop the interim strategy into a more comprehensive approach. Resolution No. 2012-25 further directed that the approach be adaptive and responsive to the results of ongoing and future research regarding vegetation on levees, knowledge gained from levee performance during high-water events, and the need to conserve critical riparian habitat. The DWR vegetation management approach described in this appendix reflects efforts to develop a more comprehensive levee vegetation management strategy that consists of efforts to manage levee vegetation, channel vegetation, and invasive plants. Levee vegetation management is particularly important because levee vegetation can impede visibility and accessibility for inspections and flood fighting, and in some limited cases, it may pose an unacceptable threat to levee integrity. In channel areas in between State Plan of Flood Control (SPFC) levees, the floodplain and channel may provide opportunities for important riparian and wetland habitat, as well as agricultural operations. However, land uses in these areas also need to be managed to maintain the channel’s ability to convey high flows during flood events. Finally, invasive plants can adversely affect operations and maintenance (O&M) of the SPFC and are a documented stressor on the species, habitats, and ecosystem processes targeted by this Conservation Strategy. Management of invasive species, and eradication of them where feasible, reduces O&M needs by increasing channel capacity and provides important ecosystem benefits.  DWR water resources managers have been implementing the interim strategy to balance public safety with environmental quality. Current and future work will focus on improving public safety by providing for integrity, visibility, and accessibility for inspections, maintenance, and flood fight operations; at the same time, protecting important and critical environmental resources. DWR’s approach also includes ongoing policy discussions regarding potential compatibility with United States Army Corps of Engineers (USACE) levee vegetation guidance through recognition of regional variations and prioritization of levee remediation based on risk assessment. Retaining lower waterside vegetation is a leading example of how risk assessment is coupled with recognition that widespread loss of habitat on levees, particularly on the lower waterside slope, is unmitigable. The Conservation Framework identified roughly two-thirds of the riparian habitat that occurs on SPFC levees is found on the lower waterside slope. On-going DWR analyses are further evaluating this assumption. In addition, risk assessment has shown that removing this vegetation, and conducting required levee remediation, likely would not be a worthwhile investment of flood risk reduction dollars. On the contrary, vegetation in this area has long been recognized as offering protection to levees from wind and wave wash erosion (USACE 1955). Expending resources to address factors contributing to lower risk would have to be considered against expending these resources to address other levee conditions that pose a significantly higher risk (DWR 2011). Similarly, DWR is assessing how to identify trees that may pose an unacceptable risk to levee integrity in a manner that retains the majority of existing habitat over its normal life span. Ongoing research, as well as knowledge gained from levee performance during high water events, will continue to inform how vegetation management within and around the SPFC may continue to evolve toward meeting multiple objectives, including sustainability of critical environmental resources. DWR anticipates revising vegetation management policy and guidance as needed in the ongoing five year updates to the CVFPP. 

CVFPP Conservation Strategy Appendix H. Central Valley Chinook Salmon Rearing Habitat Required to Satisfy the Anadromous Fish Restoration Program Doubling Goal

California Department of Water Resources (DWR) | July 14th, 2016

NewFields and Cramer Fish Sciences, in collaboration with the California Department of Water Resources FloodSAFE Environmental Stewardship and Statewide Resources

NewFields and Cramer Fish Sciences, in collaboration with the California Department of Water Resources FloodSAFE Environmental Stewardship and Statewide Resources Office Conservation Strategy team, applied best available tools and data to estimate the area of suitable juvenile salmonid rearing habitat required in each of the Conservation Planning Areas (CPAs) to achieve the Anadromous Fish Restoration Program (AFRP) “doubling goal” for Chinook salmon populations. The AFRP goal was used to align the Conservation Strategy objectives with existing,longstanding efforts by partner resource management agencies. Historical and existing suitable rearing habitat area for juvenile salmonids was estimated with the Estimated Annual Habitat approach that uses measured hydrology and modeled hydraulic relationships between river flow and inundation area to calculate areas of inundation with timing, duration, and frequency suitable for juvenile California Chinook salmon rearing. The rearing habitat required to support the doubling goal populations was estimated using the Emigrating Salmonid Habitat Estimation model. The details of the approach and the full range of calculated results are presented in the following sections and appendices.

CVFPP Conservation Strategy Appendix L. Measurable Objectives Development: Summary of Conservation Needs and Scale of Restoration Opportunities

California Department of Water Resources (DWR) | July 14th, 2016

This appendix summarizes the conservation needs and opportunities that were considered during development of measureable objectives for the Central Valley Flood Protectio

This appendix summarizes the conservation needs and opportunities that were considered during development of measureable objectives for the Central Valley Flood Protection Plan (CVFPP) Conservation Strategy (Conservation Strategy or Strategy). The summary of conservation needs is based on the needs identified in existing conservation plans for species of riverine and floodplain habitats, as further described below. The summary of conservation opportunities is based on the opportunities identified during the California Department of Water Resources (DWR’s) preliminary planning of multi-benefit flood risk reduction projects (multi-benefit projects) for the 2017 update of the CVFPP.  A Technical Advisory Workgroup (Workgroup) was convened to help DWR evaluate conservation needs and opportunities and apply this evaluation to the development of long-term measurable objectives for the Conservation Strategy. The members of the Workgroup included flood planners and managers (including the Central Valley Flood Protection Board), and biologists from resource agencies and nongovernmental organizations (NGOs). Its members provided guidance regarding the methods used to create these summaries and reviewed the preliminary results based on them.  The following sections of this appendix describe the methods used to summarize conservation needs and opportunities to, in turn, develop the measurable objectives. They also discuss the results of using those methods and provide the Workgroup’s recommendations regarding measurable objectives for the Conservation Strategy. The results are provided in Attachments 1, 2, and 3. 

Declining Groundwater Level Effects on Supply Well Operations

University of California, Davis (UC Davis) | December 1st, 2017

Pumping more from groundwater basins than they can sustainably supply decreases groundwater levels, often by undesirable amounts. Economic impacts from overdraft

Pumping more from groundwater basins than they can sustainably supply decreases groundwater levels, often by undesirable amounts. Economic impacts from overdraft and drought include increased costs for supplying water and lost revenue from inability to meet water demands. The combination of decreased groundwater level with existing well depth may limit well production as pumping costs increase and wells run dry. Declining groundwater elevations may also incur costs to move pumps deeper in the wells. Further falling groundwater elevation increases costs for production and maintenance, and decreases production capacity, as pumping levels drop into the screened intervals of wells and cause screen clogging and corrosion. In more extreme cases, well replacement costs may be incurred if groundwater drops so low that adequate submergence of pumps cannot be maintained, and wells become unusable. The potential impacts of decreasing groundwater elevation on supply well operations were evaluated for a study area in California’s Central Valley (greater vicinity of Tulare, CA). Well construction data from logs provided by the California Department of Water Resources (DWR) were characterized through statistical analysis of the elevations for the tops and bottoms of screened intervals. Groundwater elevation time series were obtained from the DWR Water Data Library. Estimated trends in well capacity loss were developed from estimates of the fraction of wells over time that had standing water levels (minus an estimated pumping drawdown) below 1) the top of the screened interval and 2) the bottom of the screened interval. The end result is a method for estimating the costs of water level declines over time from drought or groundwater overdraft due to effects on proper operation and pumping of wells. The conceptual approach, data, methods, and conclusions of this thesis draw from a research report funded by the California Department of Food and Agriculture (CDFA).

Decoupling outmigration from marine survival indicates outsized influence of streamflow on cohort success for California’s Chinook salmon populations

Canadian Journal of Fisheries and Aquatic Sciences (Canadian Science Publishing) | October 17th, 2018

Historically, marine survival estimates for salmon have been confounded with freshwater seaward migration (outmigration) survival. Telemetry studies have revealed low and

Historically, marine survival estimates for salmon have been confounded with freshwater seaward migration (outmigration) survival. Telemetry studies have revealed low and variable survival during outmigration, suggesting marine mortality may not be the primary source of variability in cohort size as previously believed. Using a novel combination of tagging technologies, survival during these two life stages was decoupled over 5 years for Sacramento River Chinook salmon (Oncorhynchus tshawytscha). Outmigration survival ranged from 2.6% to 17%, and marine survival ranged from 4.2% to 22.8%. Influential environmental drivers in both life stages were also compared with smolt-to-adult ratios (SAR) for three Chinook salmon populations over 20 years. Streamflow during outmigration had higher correlation with SAR (r2 > 0.34) than two marine productivity indices (r2 < 0.08). The few SAR estimates that were poorly predicted by flow occurred during years with the lowest marine productivity, suggesting most interannual SAR fluctuations are explained by outmigration survival, but abnormally poor marine conditions also reduce SAR. The outsized influence of flow on SAR provides managers with a powerful mitigation tool in a watershed where flow is tightly regulated.

Degradation of floodplain integrity within the contiguous United States

Nature Portfolio (Springer Nature) | June 15th, 2023

Delano Earlimart Irrigation District Groundwater Sustainability Plan

Delano Earlimart Irrigation District | January 27th, 2020

Delineation of Spatial Extent, Depth, Thickness, and Potential Volume of Aquifers Used for Domestic and Public Water-Supply in the Central Valley, California

U.S. Geological Survey (USGS) | September 5th, 2019

Identification of the groundwater resources used for drinking-water supplies is essential for the design of strategies to manage those resources. In this study, t

Identification of the groundwater resources used for drinking-water supplies is essential for the design of strategies to manage those resources. In this study, the spatial extent, depths, thicknesses, and volumes of groundwater aquifers used for domestic and public drinking-water supply were estimated from locations and well-construction data from 11,725 domestic-supply wells and 2,376 public-supply wells in the Central Valley, California. The data were compiled as part of the U.S. Geological Survey National Water Quality Assessment Project and California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment Program Priority Basin Project. The spatial distributions of the depth to top and bottom of well screens were interpolated using Empirical Bayesian Kriging across buffer areas surrounding domestic- and public-supply wells. These surfaces provide a measure of the likely maximum horizontal and vertical extent of the aquifer volume accessed for drinking water in the Central Valley during the past century. Well depth generally increased from north to south, and over time from 1905 to 2010. Well-construction depths were generally more consistent in the Sacramento Valley than in the San Joaquin Valley. The total potential aquifer volume accessed for public supply was calculated to be greater than domestic-supply access, even though the estimated spatial extent of domestic-supply wells was 1.5 times larger than the spatial extent of public-supply wells. Public-supply wells commonly have screen lengths greater than 51 meters, whereas domestic-supply wells typically have shorter screen lengths (overall median of 6 meters). Consequently, the accessed thickness and volume of the aquifer is on average 1.8 and 1.4 times greater for public-supply wells than domestic- supply wells, respectively. Results are presented as maps of areal extent, depth, and thickness of zones in the Central Valley aquifer system used for domestic and public drinking- water supplies.

Detections of current-use pesticides at 12 surface water sites in California during a 2-year period beginning in 2015

U.S. Geological Survey (USGS) | July 27th, 2018

Surface water samples were collected by the U.S. Geological Survey and multiple cooperators during base flow/irrigation runoff and storm runoff conditions from 12 sites t

Surface water samples were collected by the U.S. Geological Survey and multiple cooperators during base flow/irrigation runoff and storm runoff conditions from 12 sites throughout California, over 2 consecutive years beginning in April 2015, from both urban and agriculturally dominated watersheds. Water samples were analyzed by gas chromatography/mass spectrometry and liquid chromatrography/tandem mass spectrometry for a suite of 157 pesticides and degradates. Suspended sediments associated with these water samples were analyzed by gas chromatography/mass spectrometry for a suite of 131 pesticides and degradates. Overall, 85 pesticides and degradates were detected in the water: 32 fungicides, 25 herbicides, 27 insecticides, and 1 synergist. In the suspended sediment, 29 pesticides were detected: 9 fungicides, 10 herbicides, and 10 insecticides. Sixteen pesticides (bifenthrin, carbendazim, chlorpyrifos, clothianidin, diazinon, diuron, fenpyroximate, fipronil, fipronil sulfone, fluopicolide, imidacloprid, metolachlor, novaluron, oxyflurofen, permethrin, and simazine) were detected in the water at concentrations that were above at least one aquatic life benchmark value as defined by the U.S Environmental Protection Agency.

Development and Application of a 1D Compaction Model to Understand 65 Years of Subsidence in the San Joaquin Valley

American Geophysical Union (AGU) | June 2nd, 2022

High rates of land subsidence, caused by groundwater overdraft, are resulting in millions of dollars of infrastructure damage in California's San Joaquin Valley (SJV). In

High rates of land subsidence, caused by groundwater overdraft, are resulting in millions of dollars of infrastructure damage in California's San Joaquin Valley (SJV). In recent years, the use of interferometric synthetic aperture radar (InSAR) has enabled us to substantially improve our understanding of this subsidence. However, only very occasionally have the InSAR data been integrated with a physical model of subsurface compaction. Here, we have used InSAR and other data to parameterize and calibrate a 1D compaction model. We applied our model to a study area in the SJV where we had access to the necessary information on hydraulic head to develop model inputs. Our model simulated subsidence in the three aquifer system layers over the period 1952–2017, and is the first 1D compaction model in the SJV to simulate multiple aquifer system layers from the 1950s to 2017. The results from our model suggest that previous studies have significantly underestimated the time constants governing the slow, residual compaction of subsurface clays. We suggest that residual compaction of clays is a process that continues for decades-to-centuries, indicating that to significantly reduce subsidence requires some recovery of head, not just a stabilization. We also show how compaction in the lower, confined aquifer has accounted for over 90% of subsidence in the past 20 years. Although our study area is small, our findings are likely representative of the subsiding regions of the SJV, and our methodology can be applied to unconsolidated aquifer systems exhibiting subsidence worldwide.