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2017 Flood System Status Report
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2017 Flood System Status Report
Department of Water Resources | August 10, 2017...
Summary
This report is intended to assist flood management planners and engineers in characterizing facilities within the State Plan of Flood Control (SPFC) and...
This report is intended to assist flood management planners and engineers in characterizing facilities within the State Plan of Flood Control (SPFC) and to inform the 2017 Central Valley Flood Protection Plan Update (2017 CVFPP Update). The 2017 FSSR provides a concise repository of the status of SPFC Facilities as noted in related DWR evaluation and inspection efforts, along with the efforts of our local and federal partners. The 2012 CVFPP laid the foundation necessary for compliance with the Central Valley Flood Protection Act of 2008 and a new approach to flood management in the Central Valley.

As a supporting and informational document to the 2017 CVFPP Update, the 2017 FSSR includes information about inspecting and evaluating SPFC facilities. It also details and quantifies major components of existing flood risk within the Sacramento and San Joaquin river watersheds, and the factors that influence flood risk in relation to the various flood control structures within the SPFC. Additionally, the 2017 FSSR informs and details the current conditions of levees and channels within the SPFC, and includes finalized project information from DWR’s Levee Evaluations Program. Through updating the status of SPFC facilities, the State of California can continue to make informed decisions related to flood risk management.

This document is a collaborative effort by DWR, local, and federal partners, signifying a step forward in gaining deeper understanding of the flood system’s current status and condition in the Central Valley.

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2017 SGMA Annual Report South American Subbasin (5-021.65) Sacramento Central Groundwater Authority
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2017 SGMA Annual Report South American Subbasin (5-021.65) Sacramento Central Groundwater Authority
Sacramento Central Groundwater Authority, GEI Consultants Inc. | April 1, 2018...
Summary
The Sacramento Central Groundwater Authority (SCGA) has prepared an Annual Report describing groundwater conditions in the South American Subbasin for the 2017 Water...

The Sacramento Central Groundwater Authority (SCGA) has prepared an Annual Report describing groundwater conditions in the South American Subbasin for the 2017 Water Year (i.e., inclusive of months October 2016 to September 2017) in support of their pending Alternative Submittal. The Annual Report is intended for conveying monitoring and water use data to the State DWR on an annual basis to gauge performance of the groundwater subbasin relative to the sustainability goal set forth in a Groundwater Sustainability Plan (GSP) or, for SCGA, the Alternative Submittal. As such, SCGA is including sufficient information to provide interested parties with sufficient background and supporting details to serve as a public communications document for subbasin management and to take the place of historic biennial reporting available on the SCGA website.

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A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA
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A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA
Science of the Total Environment | June 9, 2017...
Summary
Intense demand forwater in the Central Valley of California and related increases in groundwater nitrate concentration threaten the sustainability of the groundwater resource....
Intense demand forwater in the Central Valley of California and related increases in groundwater nitrate concentration threaten the sustainability of the groundwater resource. To assess contamination risk in the region, we developed a hybrid, non-linear, machine learning model within a statistical learning framework to predict nitrate contamination of groundwater to depths of approximately 500m below ground surface.

A database of 145 predictor variables representing well characteristics, historical and current field and landscape-scale nitrogen mass balances, historical and current land use, oxidation/reduction conditions, groundwater flow, climate, soil characteristics, depth to groundwater, and groundwater age were assigned to over 6000 private supply and public supply wells measured previously for nitrate and located throughout the study area. The boosted regression tree (BRT) method was used to screen and rank variables to predict nitrate concentration at the depths of domestic and public well supplies.

The novel approach included as predictor variables outputs from existing physically based models of the Central Valley. The top five most important predictor variables included two oxidation/reduction variables (probability of manganese concentration to exceed 50 ppb and probability of dissolved oxygen concentration to be below 0.5 ppm), field-scale adjusted unsaturated zone nitrogen input for the 1975 time period, average difference between precipitation and evapotranspiration during the years 1971–2000, and 1992 total landscape nitrogen input.

Twenty-five variables were selected for the final model for log-transformed nitrate. In general, increasing probability of anoxic conditions and increasing precipitation relative to potential evapotranspiration had a corresponding decrease in nitrate concentration predictions.

Conversely, increasing 1975 unsaturated zone nitrogen leaching flux and 1992 total landscape nitrogen input had an increasing relative impact on nitrate predictions.

Three-dimensional visualization indicates that nitrate predictions depend on the probability of anoxic conditions and other factors, and that nitrate predictions generally decreased with increasing groundwater age.

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Accounting for Water “Wasted to the Sea”
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Accounting for Water “Wasted to the Sea”
San Francisco Estuary & Watershed Science | April 19, 2018...
Summary
Freshwater outflow from the Sacramento–San Joaquin Delta is a contentious management issue. Once mixed with salt water of San Francisco Bay, outflow is...
Freshwater outflow from the Sacramento–San Joaquin Delta is a contentious management issue. Once mixed with salt water of San Francisco Bay, outflow is often characterized as having no value for urban and agricultural water supply, and thus “wasted to the sea.” In the July issue of San Francisco Estuary and Watershed Science, Cloern et al. (2017) showed how outflow from the Delta provides multiple and diverse benefits to the San Francisco estuary. Rather than being “wasted,” this outflow improves ecosystem conditions and water quality, and reduces wastewater treatment costs. The Cloern et al. (2017) essay highlights the importance of considering the multiple benefits of water as it moves within and out of the Delta. To do this, however, California needs a better water accounting system. In this report, we present an alternative approach. For the period 1980–2016, we assign inflow to the Delta to four categories:

1. Water used for diversions,

2. Outflow needed to meet salinity standards for diversions,

3. Outflow to meet ecosystem regulations, and

4. Water that results in outflow because of a lack of capacity for diversion.

This approach highlights that much of the outflow from the Delta — particularly during dry periods — achieves multiple economic and environmental benefits and is hardly “wasted to the sea.”

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Adaptation of a reference site selection methodology to creeks and sloughs of California’s Sacramento Valley and alternative strategies for developing a regional bioassessment framework
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Adaptation of a reference site selection methodology to creeks and sloughs of California’s Sacramento Valley and alternative strategies for developing a regional bioassessment framework
Central Valley Regional Water Quality Control Board | November 14, 2005...
Summary
Bioassessment has shown significant promise as an effective tool for ambient water quality management in many regions of California. However, the scale and...
Bioassessment has shown significant promise as an effective tool for ambient water quality management in many regions of California. However, the scale and intensity of landscape and water transport alteration in the Central Valley pose substantial challenges to implementing bioassessment to its full potential in the region. Bioassessment programs usually are established around a careful characterization of regional reference conditions, which can be defined as the condition of waterbodies that are least impaired by human activities.

The reference condition defines a benchmark against which to infer biological impairment and to set expectations for biotic condition. Although there are several techniques available for determining reference condition, by far the most commonly applied is the use of reference sites, which are used to establish the range of natural variability in biotic condition.

We investigated the potential for identifying reference sites for segments of sloughs and creeks of the Sacramento Valley at elevations less than 85 meters. We describe here the results of a pilot study designed to adapt an existing reference site selection methodology for use in the Central Valley. Potential reference sloughs and creeks were selected on the basis of a suite of visual assessments of riparian and instream condition and qualitative GIS-based land use data.

Analysis of the benthic macroinvertebrate (BMI) assemblages collected from 30 targeted reference sites (23 creeks and 7 sloughs) was focused on addressing two main questions: 1) should creeks and sloughs be considered unique waterbody classes for the purposes of bioassessment?, 2) what is the potential for reference site based bioassessment in valley waterbodies? We addressed these questions with the BMI data using a combination of direct metric comparisons and NMS ordination. To improve our ability to interpret patterns at our 30 sites, we included two additional datasets of BMI data recently collected from nearby waterbodies.

We drew three general conclusions from this study: 1) the adaptation of reference site selection to Central Valley streams was effective; we were able to find sites in the valley to use as reference and there is enough diversity in the BMI assemblages at these reference sites to use them to detect impairment, 2) although creeks and sloughs may need to be treated as separate classes of waterbodies for bioassessment-based regulation, there is evidence to suggest that the differences are not clear-cut and the question needs further investigation, 3) BMI assemblages in valley floor reference sites are clearly different from those in foothill reference sites.

We discuss the potential for reference site based determination of reference conditions and summarize the current state of the science for defining reference condition in regions without adequate reference sites. We also list a set of recommendations that the Central Valley Regional Water Quality Control Board should consider while constructing a defensible framework for bioassessment in the Central Valley.

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Adaptation Strategies for Agricultural Sustainability in Yolo County, California
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Adaptation Strategies for Agricultural Sustainability in Yolo County, California
California Energy Commission | July 31, 2012...
Summary
This place?based case study in an agricultural county in California’s Central Valley focused on the period of 2010–2050, and dealt with biophysical and...
This place?based case study in an agricultural county in California’s Central Valley focused on the period of 2010–2050, and dealt with biophysical and socioeconomic issues related to both mitigation of greenhouse gas (GHG) emissions and to adaptation to an uncertain climate. In the past 100 years, changes in crop acreage has been more related to crop price and availability of irrigation water than to growing degree days during summer, and in fact, summer temperatures have increased less than winter temperatures. Econometric analysis indicated that warmer winters, as projected by Geophysical Fluid Dynamics Laboratory?Bias Corrected Constructed Analog during 2035–2050, could result in less wheat acreage, more alfalfa and tomato acreage, and slight effects on tree and vine crops. The Water Evaluation and Planning (WEAP) model showed that these econometric projections did not reduce irrigation demand under either the B1 or A2 scenarios, but a diverse, water?efficient cropping pattern combined with improved irrigation technology reduced demand to 12 percent below the historic mean.

Collaboration during development of Yolo County’s Climate Action Plan showed that nitrous oxide (mainly from nitrogen fertilizers) was the main source (?40 percent) of agricultural emissions. Emissions from cropland and rangeland were several orders of magnitude lower than urbanized land per unit area. A survey distributed to 570 farmers and ranchers achieved a 34 percent response rate. Farmers concerned about climate change were more likely to implement water conservation practices, and adopt voluntary GHG mitigation practices.

Use of the urban growth model (UPlan) showed that channeling much or all future urban development into existing urban areas will increase ecosystem services by preserving agricultural land and open space, immensely reducing the Yolo County’s GHG emissions, and greatly enhancing agricultural sustainability.

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Agricultural Irrigation in This Drought: Where is the Water and Where Is It Going?
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Agricultural Irrigation in This Drought: Where is the Water and Where Is It Going?
University of California Giannini Foundation of Agricultural Economics | May 14, 2015...
Summary
In the midst of its fourth year of drought, California now faces an estimated reduction in surface-water availability of 8.8 million acre-feet (maf)...
In the midst of its fourth year of drought, California now faces an estimated reduction in surface-water availability of 8.8 million acre-feet (maf) out of 29 maf in agricultural applied water statewide. However, groundwater, the buffer water supply during drought, is replacing about 6.2 maf of surface water via additional pumping. This increased groundwater pumping is in addition to the 1.5 maf of annual average groundwater overdraft in the Central Valley. The net reduction of 2.6 maf in the total supply in 2015 may result in about 564,000 acres fallowed statewide, or about 120,000 more acres than last year's fallowing estimates.

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An Index of Biotic Integrity (IBI) for Perennial Streams in California’s Central Valley

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An Index of Biotic Integrity (IBI) for Perennial Streams in California’s Central Valley
California State Water Resources Control Board | December 1, 2008...
Summary
Bioassessment is the science of using aquatic organisms as indicators of ecological condition in streams in rivers. Many types of organisms can be...

Bioassessment is the science of using aquatic organisms as indicators of ecological condition in streams in rivers. Many types of organisms can be used as indicators, for example fish or algae, but bioassessment is most frequently based on benthic macroinvertebrates (BMIs), which are small but visible bottom-dwelling organisms such as insects. BMI data sets typically consist of long lists of species (or taxa) found in a sample and their relative abundances. These data can be simplified into measures of biological condition such as indices of biotic integrity (IBIs) that are designed to be sensitive to human-caused alterations to the landscape, to stream channels and riparian zones, and to water chemistry. IBIs function much like economic indicators: high IBI scores reflect good ecological conditions while low IBI scores reflect poor ecological conditions.

Bioassessment is increasingly used throughout California by water quality monitoring programs, but in the Central Valley bioassessment is more challenging than in other regions of the state because the entire landscape and most streams are highly altered by human activities such as urbanization, agriculture and water diversions. This makes it impossible to evaluate how BMIs respond across a complete gradient of human disturbance within the region, that is, from minimally disturbed reference sites where human activity is absent or minimal and which therefore set the benchmark for biological expectations, to the most altered sites with degraded biology. In the Central Valley, minimally disturbed reference sites are no longer available. Even the ‘least-disturbed’ sites, which represent the best-available chemical, physical and biological habitat conditions given the current state of the landscape, are markedly disturbed. Reference sites in other parts of California, such as the Sierra Nevada or the Sierra foothills, may be significantly less disturbed than Central Valley reference sites.

In this study, BMI data sets from 11 studies conducted at various intervals over the last 14 years were compiled to build an IBI for Central Valley streams. Data were not collected consistently by the different studies, and many gaps were present in associated physical habitat and water chemistry data sets. This could be corrected for BMI samples by standardizing to a consistent level of taxonomic effort. Gaps in other data could not be addressed. Criteria for defining ‘best-available’ reference sites were established as data allowed and were based on local urban and agricultural intensity, stream channel and riparian condition, and stream substrate composition. Eighty BMI metrics were evaluated for inclusion in the IBI based on 4 criteria: 1) sufficient range for scoring; 2) responsiveness to land use and/or local disturbance variables measured at the 150-meter sampling reach (as data allowed); 3) good discrimination between reference and test sites; 4) lack of correlation with other responsive metrics. Five final metrics were selected and scored for inclusion in the IBI: collector richness (number of taxa that are collector- feeders), predator richness (number of taxa that are predators), percent EPT taxa (percent of taxa that are mayflies, stoneflies, or caddisflies), percent clinger taxa (percent of taxa that cling to vegetation) and Shannon diversity (a composite measure of taxonomic richness and evenness of abundance). The final IBI showed good discrimination between reference and test sites, and was validated with an independent data set. BMI metrics and the final IBI were more strongly related to reach-scale physical habitat variables than to water chemistry or land use variables, but detailed water chemistry was lacking for many sites, and some studies have shown that response to land use diminishes when more than 10% of a watershed is degraded by human activities.

Despite data gaps that were less than ideal for indicator development, this study is the first to set expectations for Central Valley BMI assemblages based on best-available reference sites. The Central Valley IBI can be used as a general interpretive framework for benthic samples collected from perennial streams on the valley floor and provides an objective means for rating biological condition in a region with high urban and agricultural intensity. The ability to rank sampling sites relative to explicitly defined biological expectations is essential to any biological monitoring program. Therefore, this index may prove useful in several monitoring applications, including California’s non- point source CMAP program where sampling was stratified to assess and compare stream condition in urban, agricultural and forested watersheds, in stormwater monitoring programs, in point-source pollution investigations, and in stream restoration monitoring. Key recommendations include: 1) that all future bioassessment projects in the Central Valley should collect quantitative physical habitat and water chemistry with consistent protocols at all sites; in situ chemistry and rapid (qualitative) physical habitat are not sufficient for screening reference sites or evaluating BMI responses to stressor gradients; 2) that bioassessment should be added to NPS monitoring where programs are already collecting more intensive stressor data such as pesticides, nutrients and metals. This will provide California’s monitoring programs with better datasets to support future analyses.

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Assessment of Interconnected Subbasins

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Assessment of Interconnected Subbasins
Butte County | June 30, 2017...
Summary
The Sustainable Groundwater Management Act (SGMA) requires groundwater sustainability agencies (GSAs) to develop groundwater sustainability plans (GSPs) that achieve sustainable groundwater management within...
The Sustainable Groundwater Management Act (SGMA) requires groundwater sustainability agencies (GSAs) to develop groundwater sustainability plans (GSPs) that achieve sustainable groundwater management within 20 years of adoption. All critically overdrafted basins must adopt GSPs by January 31, 2020; all other medium and high priority basins must complete GSPs by January 31, 2022. Since many subbasins are hydrologically connected to adjoining subbasins, sustainable groundwater management will require accounting for groundwater interactions with adjoining subbasins. Often, adjoining subbasins will use different analytical methods or apply different levels of technical rigor. Many GSAs are concerned that different methodologies for developing interbasin flows can lead to different results that will call into question the ability to achieve sustainability and would potentially create issues with SGMA compliance.

This effort evaluated opportunities and barriers for agencies to account for interconnected basin dynamics through the collaboration of technical experts focused on a portion of the northern Sacramento Valley Integrated Regional Water Management (NSVIRWM) Plan area. As interbasin flows (i.e., groundwater flow between interconnected basins) cannot be directly measured, the project reviewed available tools to investigate how they may or may not be suitable for use in estimating interbasin flows within the region. This process highlighted areas for local agencies to consider in addressing interbasin issues, developed a framework for analysis in other areas of the state, and identified areas where the state and federal government can assist local agencies implementing SGMA. This report is developed to provide summary level information appropriate for decision makers, with more detailed technical information and examples provided in the appendices or by reference.

Interbasin flow is groundwater entering or exiting a defined subbasin through its boundaries in the subsurface and may vary significantly in space and time based on the dynamics of inflow and outflow from the basins. Interbasin flows are driven by differences in groundwater levels (i.e. head gradients) across the basin boundary. Groundwater levels are, in turn, impacted by processes on the land surface. Land use and crop acreages drive water demand in a subbasin and indirectly drive groundwater pumping, which has a direct effect on groundwater levels (i.e., groundwater heads). The direction and magnitude of interbasin flow depends on the groundwater head gradient across the basin boundary and the conductivity of the aquifer materials.

It is widely recognized that the groundwater subbasins in the Sacramento Valley, and throughout the Central Valley, are interconnected to varying degrees. The Sacramento Valley Groundwater Basin includes many subbasins, extends over a wide geographic area, and includes numerous established and eligible GSAs. With interconnected subbasins, management decisions and actions in one subbasin may influence one or more adjoining subbasins. Such influence may positively or negatively impact sustainability. Thus, interbasin flows become critical to both GSAs’ development of GSPs and to DWR reviewing GSPs.

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Assessment of Interconnected Subbasins: Regional Collaboration and Model Selection Process

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Assessment of Interconnected Subbasins: Regional Collaboration and Model Selection Process
Groundwater Resources Association of California | October 3, 2017...
Summary
In basins with complex spatial and temporal variations in water budget components, integrated groundwater-surface water modeling is the best approach to quantify and...
In basins with complex spatial and temporal variations in water budget components, integrated groundwater-surface water modeling is the best approach to quantify and evaluate interbasin groundwater flows.

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Availability of high-magnitude streamflow for groundwater banking in the Central Valley, California
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Availability of high-magnitude streamflow for groundwater banking in the Central Valley, California
Environmental Research Letters | July 31, 2017...
Summary
California’s climate is characterized by the largest precipitation and streamflow variability observed within the conterminous US This, combined with chronic groundwater overdraft of...

California’s climate is characterized by the largest precipitation and streamflow variability observed within the conterminous US This, combined with chronic groundwater overdraft of 0.6–3.5 km3 yr 1, creates the need to identify additional surface water sources available for groundwater recharge using methods such as agricultural groundwater banking, aquifer storage and recovery, and spreading basins. High-magnitude streamflow, i.e. flow above the 90th percentile, that exceeds environmental flow requirements and current surface water allocations under California water rights, could be a viable source of surface water for groundwater banking. Here, we present a comprehensive analysis of the magnitude, frequency, duration and timing of high-magnitude streamflow (HMF) for 93 stream gauges covering the Sacramento, San Joaquin and Tulare basins in California. The results show that in an average year with HMF approximately 3.2 km3 of high-magnitude flow is exported from the entire Central Valley to the Sacramento-San Joaquin Delta often at times when environmental flow requirements of the Delta and major rivers are exceeded. High-magnitude flow occurs, on average, during 7 and 4.7 out of 10 years in the Sacramento River and the San Joaquin-Tulare Basins, respectively, from just a few storm events (5–7 1-day peak events) lasting for 25–30 days between November and April. The results suggest that there is sufficient unmanaged surface water physically available to mitigate long-term groundwater overdraft in the Central Valley.

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Before the Well Runs Dry: Improving the Linkage Between Groundwater and Land Use Planning

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Before the Well Runs Dry: Improving the Linkage Between Groundwater and Land Use Planning
Water in the West, Stanford Woods Institute for the Environment, The Bill Lane Center for the American West | April 17, 2014...
Summary
There is no comprehensive regulation of groundwater use in the state of California,* and the right to withdraw groundwater is based on surface...
There is no comprehensive regulation of groundwater use in the state of California,* and the right to withdraw groundwater is based on surface land ownership. This creates a direct linkage between every land use that requires water and the groundwater underneath that land. Because so many aspects of groundwater use are not regulated by the state, local governments’ land use decisions become a key driver of demands on groundwater. Nonetheless, land use decisions and planning are not well coordinated with groundwater management.

Understanding how land use decisions affect groundwater resources has become increasingly important in recent years, as groundwater provides approximately 30 percent of California’s water supply in average years and 40 percent of the supply in dry years. In some places, the reliance on groundwater during droughts is much higher, due to reduced supplies of surface water. Growth from housing and irrigated agriculture, among other demands, have led to chronic overdraft and declining groundwater elevations in many communities that rely heavily on groundwater.

To address this problem, Water in the West convened groundwater managers, land use planners, water lawyers, consultants and academics at Stanford University for an Uncommon Dialogue in the fall of 2013. Its aim was to discuss a growing consensus that more effective integration of land use planning and groundwater management is an essential component of preserving groundwater aquifers for the future, and to share possible means of accomplishing this in California.

This report, shaped in part by the Dialogue, provides the background and regulatory context for land use planning and groundwater management in California, shares case studies that highlight the intersection of groundwater and land use, and makes specific recommendations to improve the linkage between land use decisions and groundwater management in the state.

*The Sustainable Groundwater Management Act (SGMA) was signed into law five months after this was published.

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California Water Plan 2013: Sacramento River Hydrologic Region Report
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California Water Plan 2013: Sacramento River Hydrologic Region Report
Department of Water Resources | October 30, 2014...
Summary
The Sacramento River Hydrologic Region (see Figure SR-1 includes the entire California drainage area of the Sacramento River (the state’s largest river) and...
The Sacramento River Hydrologic Region (see Figure SR-1 includes the entire California drainage area of the Sacramento River (the state’s largest river) and its tributaries. The region extends from Chipps Island in Solano County north to Goose Lake in Modoc County. It is bounded by the Sierra Nevada on the east, the Coast Ranges on the west, the Cascade and Trinity
mountains on the north, and the Sacramento-San Joaquin River Delta (Delta) on the south. The Sacramento River Basin actually begins in Oregon, north of Goose Lake, a near-sink that intercepts the Pit River drainage at the California-Oregon border.

Some key issues for this region are summarized here and discussed further later in this report.

Agriculture. Between 2005 and 2010, the region supported about 1.95 million acres of irrigated agriculture on average. Approximately 1.58 million acres is irrigated on the valley floor. The surrounding mountain valleys add about 370,000 irrigated acres to the region’s total — primarily as pasture and alfalfa. The gross value of agricultural production in the Sacramento Valley for 2011 was about $4.1 billion (California Department of Food and Agriculture 2013). Rice and walnuts are the highest grossing crops in the region followed by almonds and tomatoes. The direct, indirect, and induced effects of the agricultural industry to the regional economy are discussed in this report.

Groundwater. With a 2005-2010 average annual extraction volume of 2.7 million acre-feet (maf), groundwater pumping in the Sacramento River Hydrologic Region accounts for 17 percent of all the groundwater extraction in California — the third highest among the 10 hydrologic regions in California, behind Tulare Lake Hydrologic Region with 38 percent and San Joaquin River Hydrologic Region with 19 percent of the total. Overall, groundwater contributes to about 31 percent of the total water supply. Most groundwater extraction in the region occurs for agricultural water use (2.4 maf), meeting about one-third of agricultural water demands. Groundwater extraction for urban water use is significantly less (465 thousand acre-feet [taf]), which meets about half of the urban water needs. Groundwater levels for much of the region have declined from 2005 to 2010. Groundwater level declines ranging from 20 to 30 feet are seen in the northwestern portion of the Sacramento Valley Groundwater Basin. Declines ranging from to 10 to 20 feet are seen in the northern, the mid- to south-western, and the southeastern portions of the valley. For the rest of the Sacramento Valley Groundwater Basin and the Redding Area Groundwater Basin, groundwater level declines have
ranged from zero to 10 feet.

Flood. Exposure to a 500-year flood event in the region threatens approximately one in three residents, almost $65 billion in assets (crops, buildings, and public infrastructure), 1.2 million acres of agricultural land, and over 340 sensitive species. Almost 95 percent of Sutter County residents, more than 55 percent of Yuba County and Yolo County residents, and more than 50 percent of agricultural land region-wide are exposed to the 500-year flood event.

Climate Change. Several different climate regions overlie portions of the Sacramento River Hydrologic Region. Air temperature data collected for the past century has been summarized by the Western Regional Climate Center (WRCC) for the different regions which are outlined below.
- Within the WRCC North Central climate region, mean temperatures have increased by about 0.8 to 1.7 °F (0.4 to 0.9 °C) in the past century, with minimum and maximum temperatures increasing by about 1.2 to 2.1 °F (0.7 to 1.2 °C) and 0.1 to 1.5 °F (0.1 to 0.8 °C), respectively.
- Within the WRCC North East climate region, mean temperatures have increased by about 0.8 to 2.0 °F (0.5 to 1.1 °C) in the past century, with minimum and maximum temperatures increasing by about 0.9 to 2.2 °F (0.5 to 1.2 °C) and by 0.5 to 2.1 °F (0.3 to 1.2 °C), respectively.
- Within the WRCC Sierra climate region, mean temperatures have increased by about 0.8 to 2.0 °F (0.5 to 1.1 °C) in the past century, with minimum and maximum temperatures increasing and decreasing by about 1.7 to 2.8 °F (0.9 to 1.5 °C) and by -0.2 to 1.3 °F (-0.1 to 0.7 °C), respectively.
- Within the WRCC Sacramento-Delta climate region, mean temperatures have increased by about 1.5 to 2.4 °F (0.9 to 1.3 °C) in the past century, with minimum and maximum temperatures increasing by about 2.1 to 3.1 °F (1.2 to 1.7 °C) and by 0.8 to 2.0 °F (0.4 to 1.1 °C), respectively (Western
  Regional Climate Center 2013).
The region also is currently experiencing impacts from climate change through changes in statewide precipitation and surface runoff volumes, which in turn affect availability of local and imported water supplies. During the last century, the average early snowpack in the Sierra
Nevada decreased by about 10 percent, which equates to a loss of 1.5 maf of snowpack storage (California Department of Water Resources 2008). Projections and impacts based on modeling of climate change are included in this report.
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California’s Central Valley Groundwater Study: A Powerful New Tool to Assess Water Resources in California’s Central Valley
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California’s Central Valley Groundwater Study: A Powerful New Tool to Assess Water Resources in California’s Central Valley
U.S. Geological Survey (USGS) | June 16, 2009...
Summary
Competition for water resources is growing throughout California, particularly in the Central Valley. Since 1980, the Central Valley’s population has nearly doubled to...

Competition for water resources is growing throughout California, particularly in the Central Valley. Since 1980, the Central Valley’s population has nearly doubled to 3.8 million people. It is expected to increase to 6 million by 2020. Statewide population growth, anticipated reductions in Colorado River water deliveries, drought, and the ecological crisis in the Sacramento–San Joaquin Delta have created an intense demand for water. Tools and information can be used to help manage the Central Valley aquifer system, an important State and national resource.

The U.S. Geological Survey (USGS) has released results from a study on the largest water reservoir in the State of California, the Central Valley groundwater system. The findings show continued loss of stored groundwater in the southern part of the valley (see figure below). Since about 1960, groundwater has been depleted by almost 60 million acre-feet, which is, on average, enough to supply every resident of California with water for 8 years. In order to complete the study, the USGS developed an extensive, detailed three-dimensional (3D) computer model of the hydrologic system of the Central Valley (Faunt, 2009). The Central Valley Hydrologic Model (CVHM) simultaneously accounts for changing water supply and demand across the landscape, and simulates surface water and groundwater flow across the entire Central Valley.

This new hydrologic modeling tool can be used by water managers to understand how water moves through the aquifer system, predict water-supply scenarios, and address issues related to water competition in California and the Central Valley including: • Conjunctive water use (interdependent use of surface water and groundwater); • Conservation of agricultural land; • Land-use change, including environmental concerns and urbanization, and its effects on water resources; and • Effects of climate change.

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California’s Severe Drought Has Only Marginal Impacts on Food Prices

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California’s Severe Drought Has Only Marginal Impacts on Food Prices
University of California Giannini Foundation of Agricultural Economics | May 14, 2015...
Summary
The extreme drought that has gripped California over the past several years is causing onerous adjustments in the natural and human environments. Agriculture,...
The extreme drought that has gripped California over the past several years is causing onerous adjustments in the natural and human environments. Agriculture, which uses much of the state’s water, is at the center of many of these arduous responses. The 2015 impacts of the continuing drought are still underway, but in this special Agriculture and Resource Economics Update issue, we project responses and consequences within agriculture and more broadly. In this issue, Hanak and Mount put this drought in the context of California’s history and put agriculture in the context of water institutions, management, and distribution throughout the state. Next, Medellin-Azuara and co-authors develop detailed, and albeit preliminary, assessments of 2015 irrigation water distribution. They estimate a cut to agriculture of about 8.8 million acre-feet, or about 30% of what might be available in a normal year. (This number may be an underestimate given recent events.) During droughts, farms increase groundwater pumping. The authors estimate that farmers and ranchers will replace about 6.2 million acre-feet of lost surface water deliveries with costly increases in groundwater pumping, where possible in 2015.

Another painful response to drought is to leave land idle. The authors estimate about 564,000 more acres, mostly field crop land in the Central Valley (including irrigated pastures), will be idled in 2015. This too may be an underestimate. USDA reported on June 30, that 2015 California acreage of “principal crops,” (defined as field crops such as hay, grains, oilseeds, cotton and potatoes) is about 900,000 acres below the 2013 total of about four million acres. Over this period, tree nut and tomato acreage increased by about 180,000 acres. So, even accounting for the steady shift to tree nuts and some other higher revenue per acre (and per acre-foot) crops, there is a strong indication of severely accelerated reductions in field crop acreage in California.

The economic toll of the drought is fewer jobs and smaller value of output and economic contribution that would have otherwise occurred. Based on 564,000 idled acres, Howitt et al. estimates farm revenue losses of $1.8 billion, economy-wide revenue losses of $2.7 billion, and 18,600 fewer jobs due to the agricultural drought. That these economic impacts are not even larger is a testament to the extraordinary efforts and innovations by farmers, and others in California agriculture. Idling land, shifting water across crops, and using each acre-foot more economically all have led to smaller losses of revenue and jobs, and only very small price increases for consumers.

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Central Valley Flood Protection Plan (2012)
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Central Valley Flood Protection Plan (2012)
Department of Water Resources | June 12, 2012...
Summary
The Central Valley Flood Protection Plan (CVFPP) is a critical document to guide California’s participation (and influence federal and local participation) in managing...
The Central Valley Flood Protection Plan (CVFPP) is a critical document to guide California’s participation (and influence federal and local participation) in managing flood risk along the Sacramento River and San Joaquin River systems. The CVFPP proposes a system-wide investment approach for sustainable, integrated flood management in areas currently protected by facilities of the State Plan of Flood Control (SPFC).

The CVFPP will be updated every five years, with each update providing support for subsequent policy, program, and project implementation.

The State of California (State) conducted planning and investigations for the 2012 CVFPP from 2009 through 2011, representing the most comprehensive flood evaluations for the Central Valley. Following the anticipated adoption of the CVFPP in 2012 by the Central Valley Flood Protection Board (Board), preparation of regional- and State-level financing plans will guide investments in the range of $14 billion to $17 billion during the next 20 to 25 years. These financing plans are critical to CVFPP implementation, given the uncertainty in State, federal, and local agency budgets and cost-sharing capabilities.

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Central Valley Flood Protection Plan: Conservation Strategy

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Central Valley Flood Protection Plan: Conservation Strategy
Department of Water Resources | August 8, 2017...
Summary
In the Central Valley of California, flood risks, water supplies, and the functioning of ecosystems are linked, with actions in one area affecting...
In the Central Valley of California, flood risks, water supplies, and the functioning of ecosystems are linked, with actions in one area affecting the other areas. The majority of flows that pass through the State Plan of Flood Control (SPFC) are regulated by reservoirs operated for flood management, water supply, water quality, power generation, wildlife and fisheries habitat, and recreation. Similarly, the system of river and bypass channels, levees, and water control structures in the Central Valley does more than just contain floodwaters that previously flooded the valley floor for months at a time. It supports agricultural uses in the bypasses, serves as valued recreational areas and open space, helps in the management of surface water supplies and management of groundwater and water quality, and provides critical remnant riparian and floodplain habitats for numerous fish and wildlife species.

The Central Valley Flood Protection Plan (CVFPP) recognizes these interconnections in its approach to flood management. The CVFPP is a long-term planning document that provides a framework for prioritization of investments in the SPFC. It seeks to improve flood risk management (the primary goal), as well as improve operations and maintenance (O&M), promote ecosystem functions, improve institutional support, and promote multi-benefit projects where feasible (supporting goals) (California Department of Water Resources [DWR] 2012a).

This Conservation Strategy (or Strategy) is an integral part of the CVFPP. It supports the attainment of all CVFPP goals, but focuses on the improvement of ecosystem functions through the integration of ecological restoration with flood risk reduction projects where feasible. This Conservation Strategy, including Appendices A?L, describes the basis for recommending various conservation actions and setting long-term objectives for the Central Valley flood management system as a whole. The integration of specific environmental restoration features with DWR’s proposed flood management system improvements is summarized in Chapters 2 and 3 of the CVFPP and will also be described further in the 2017 CVFPP update and supporting documents, such as the Sacramento River Basin-Wide Feasibility Study (BWFS) and the San Joaquin River BWFS.

The Conservation Strategy and CVFPP as a whole would contribute to achieving the California Water Action Plan’s overarching goals of reliability, restoration, and resilience (California Natural Resources Agency, California Department of Food and Agriculture, and California Environmental Protection Agency 2015, 2016). In particular, this Strategy and the CVFPP as a whole are integral to three of the 10 “key actions” identified in the California Water Action Plan:

Increase flood protection.
Protect and restore important ecosystems.
Increase operational and regulatory efficiency.

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Central Valley Project (CVP) Water Transfer Program Fact Sheet

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Central Valley Project (CVP) Water Transfer Program Fact Sheet
U.S. Bureau of Reclamation | February 1, 2015...
Summary
Water transfers and exchanges are an integral part of CVP water operations, particularly in drought years, as long as transfers can occur consistent...

Water transfers and exchanges are an integral part of CVP water operations, particularly in drought years, as long as transfers can occur consistent with state and federal laws governing water transfers. In 2014, Reclamation facilitated the transfer of over 257,000 acre-feet of water. Of the 257,000 acre-feet, 213,220 acre-feet was considered “new water” to the system, meaning specific actions (such as reservoir reoperation, crop idling/shifting, groundwater substitution, or Yuba Accord purchases) were taken to make the water available. The remaining quantity was considered an in-basin transfer or a reallocation of contract supply.

• §3405(a) of the Central Valley Project Improvement Act of 1992 (CVPIA) authorizes the transfer of all or a portion of a CVP contractors contracted water supply to any other California water user or water agency, State or Federal agency, Indian Tribe, or private non-profit organization for project purposes or any purpose recognized as beneficial under State law.

• CVP water transfers are subject to the conditions prescribed in §3405(a), 1993 Interim Guidelines for Implementation of Water Transfers, and the Department of the Interior Final CVPIA Administrative Proposal on Water Transfers (1998).

• Water transfer provisions of CVPIA do not apply to permanent contract assignments under which a CVP contractor relinquishes their contractual right to Project water; water banking and recharge actions outside of the contractors boundaries; water for water exchanges; forbearance actions whereby CVP contractors are paid not to exercise their right to water; and transfers of base supply water under settlement contracts which are carried out in accordance with State law.

• Since 1992, the Region and the State of California Department of Water Resources, owners and operators of the two largest water projects in California, have collaborated to develop criteria to facilitate water transfers.

• The Region facilitates both short and long-term transfers of CVP water. Long-term transfer approvals are accomplished through programmatic environmental documentation, with annual approvals of physical water transfers.

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Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS)
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Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS)
Central Valley Salinity Coalition (CVSC) | January 19, 2017...
Summary
Elevated salinity and nitrates in surface water and groundwater are increasing problems affecting much of California, other western states, and arid regions throughout...
Elevated salinity and nitrates in surface water and groundwater are increasing problems affecting much of California, other western states, and arid regions throughout the world. In California, as surface and groundwater supplies become scarcer, and as wastewater streams become more concentrated, salinity and nitrate impairments are occurring with greater frequency and magnitude.

In 2006, the Central Valley Water Board, the State Water Board, and stakeholders began a joint effort to address salinity and nitrate problems in California’s Central Valley and adopt long-term solutions that will lead to enhanced water quality and economic sustainability. Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) is a collaborative basin planning effort aimed at developing and implementing a comprehensive salinity and nitrate management program. The goal of CV-SALTS is to maintain a healthy environment and a good quality of life for all Californians by protecting our most essential and vulnerable resource: WATER.

In July 2008, the Central Valley Salinity Coalition (CVSC) was formed. CVSC represents stakeholder groups working with the Board in the CV-SALTS effort. Its purpose is to organize, facilitate and fund efforts needed to fulfill the goals of CV-SALTS. CVSC coordinates the meetings of the CV-SALTS committees, maintains an independent web site, and manages the projects originating from this effort. Information and materials regarding the stakeholder committees and other activity, including the meeting schedule, are posted on their website: www.cvsalinity.org.

The Final SNMP for Central Valley Water Board Consideration was completed in December 2016. The Central Valley Water Board staff plans to release this version of the SNMP and all of its supporting attachments in January 2017 for a comment period so that the public has the opportunity to review the SNMP documentation before a general information workshop is held with the Central Valley Water Board, currently planned for March 2017.

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Climate Change and the Delta: A Synthesis (Public Review Draft)

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Climate Change and the Delta: A Synthesis (Public Review Draft)
Delta Stewardship Council | March 23, 2018...
Summary
The Delta Reform Act of 2009 (Water Code Section 85066) requires that the Delta Stewardship Council adopt a Delta Plan (the Plan) to...
The Delta Reform Act of 2009 (Water Code Section 85066) requires that the Delta Stewardship Council adopt a Delta Plan (the Plan) to achieve the coequal goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem (Water Code Section 85000). In the time since the Plan was adopted in 2013, a significant shift in State planning for Delta ecosystem protection, restoration, and enhancement has occurred, prompting review of the Delta Plan to examine whether its strategies are still suited to achieve the ecological goals of the Delta Reform Act. As such, the Delta Stewardship Council (Council) is developing an amendment of the Plan’s Chapter 4, Protect, Restore, and Enhance the Delta Ecosystem.

Council staff are reviewing the best-available science to inform amendment of Chapter 4 of the Delta Plan. To support this effort, Council staff have developed three science synthesis papers. This paper focuses on the effects of climate change in the Delta and is accompanied by two other papers focused on the Delta ecosystem (terrestrial and aquatic resources) and restoration. Climate change is of interest for the Chapter 4 amendment given recent rapid advancements in research on climate change and its effects on the Delta ecosystem that have occurred since the Delta Plan was adopted in 2013 (Dettinger et al. 2016).

Climate change has the potential to significantly affect the Delta ecosystem by raising air and water temperatures, changing the timing and volume of flows into and through the Delta, increasing tidal inundation with sea-level rise (SLR), and increasing salinity intrusion into the Delta. Climate change is recognized as a global stressor in Chapter 4 of the 2013 Delta Plan, but the effects of climate change on Delta ecosystems are discussed only briefly and with limited consideration of management strategies that address the issue. Chapter 4 of the Delta Plan identifies five key stressors to the Delta ecosystem and core strategies for addressing each. Climate change has interrelated effects on all five core strategy areas: Delta flows, habitat, water quality, non-native 28 species, and hatcheries and harvest management.

The Delta Reform Act specifies consideration of “the future impact of climate change and sea-level rise” (Water Code Section 85066), and identifies a restoration timeline horizon of 2100 (Water Code Section 85302). More generally, Executive Order B-30-15, signed by Governor Brown in April 2015, requires that State agencies incorporate climate change into planning and investment decisions, and that they prioritize natural infrastructure and actions for climate preparedness.

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2017 Flood System Status Report

2017 Flood System Status Report

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2017 SGMA Annual Report South American Subbasin (5-021.65) Sacramento Central Groundwater Authority

2017 SGMA Annual Report South American Subbasin (5-021.65) Sacramento Central Groundwater Authority

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A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA

A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA

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Accounting for Water “Wasted to the Sea”

Accounting for Water “Wasted to the Sea”

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Adaptation of a reference site selection methodology to creeks and sloughs of California’s Sacramento Valley and alternative strategies for developing a regional bioassessment framework

Adaptation of a reference site selection methodology to creeks and sloughs of California’s Sacramento Valley and alternative strategies for developing a regional bioassessment framework

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Adaptation Strategies for Agricultural Sustainability in Yolo County, California

Adaptation Strategies for Agricultural Sustainability in Yolo County, California

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Agricultural Irrigation in This Drought: Where is the Water and Where Is It Going?

Agricultural Irrigation in This Drought: Where is the Water and Where Is It Going?

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An Index of Biotic Integrity (IBI) for Perennial Streams in California’s Central Valley

An Index of Biotic Integrity (IBI) for Perennial Streams in California’s Central Valley

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Assessment of Interconnected Subbasins

Assessment of Interconnected Subbasins

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Assessment of Interconnected Subbasins: Regional Collaboration and Model Selection Process

Assessment of Interconnected Subbasins: Regional Collaboration and Model Selection Process

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Availability of high-magnitude streamflow for groundwater banking in the Central Valley, California

Availability of high-magnitude streamflow for groundwater banking in the Central Valley, California

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Before the Well Runs Dry: Improving the Linkage Between Groundwater and Land Use Planning

Before the Well Runs Dry: Improving the Linkage Between Groundwater and Land Use Planning

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California Water Plan 2013: Sacramento River Hydrologic Region Report

California Water Plan 2013: Sacramento River Hydrologic Region Report

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California’s Central Valley Groundwater Study: A Powerful New Tool to Assess Water Resources in California’s Central Valley

California’s Central Valley Groundwater Study: A Powerful New Tool to Assess Water Resources in California’s Central Valley

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California’s Severe Drought Has Only Marginal Impacts on Food Prices

California’s Severe Drought Has Only Marginal Impacts on Food Prices

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Central Valley Flood Protection Plan (2012)

Central Valley Flood Protection Plan (2012)

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Central Valley Flood Protection Plan: Conservation Strategy

Central Valley Flood Protection Plan: Conservation Strategy

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Central Valley Project (CVP) Water Transfer Program Fact Sheet

Central Valley Project (CVP) Water Transfer Program Fact Sheet

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Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS)

Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS)

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Climate Change and the Delta: A Synthesis (Public Review Draft)

Climate Change and the Delta: A Synthesis (Public Review Draft)

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