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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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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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Applying the Connectivity Approach: Groundwater management in California’s Kings Basin
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Applying the Connectivity Approach: Groundwater management in California’s Kings Basin
California Roundtable on Water and Food Supply | March 27, 2015...
Summary
The California Roundtable on Water and Food Supply (CRWFS) studied the processes used in the Kings Groundwater Subbasin (Kings Basin) of California’s San...
The California Roundtable on Water and Food Supply (CRWFS) studied the processes used in the Kings Groundwater Subbasin (Kings Basin) of California’s San Joaquin Valley to reveal strategies for advancing groundwater sustainability within the context of watershed-scale, integrated water management.

This inquiry was guided by the principles of the “connectivity approach”: a framework developed by CRWFS for resource managers, land use planners and policymakers to discover the linkages, strengths, successes, potentials, and disconnects related to their particular resource stewardship issues. A key concept is connected benefits, which refers to achieving multiple benefits across resource and development sectors to respond to California’s increasing water management challenges.

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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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Better late than never: a synthesis of strategic land retirement and restoration in California

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Better late than never: a synthesis of strategic land retirement and restoration in California
Ecosphere | August 10, 2018...
Summary
Strategic retirement and restoration of agricultural lands is a critical conservation opportunity globally. The objective of this synthesis was to examine whether ecological habitat...
Strategic retirement and restoration of agricultural lands is a critical conservation opportunity globally. The objective of this synthesis was to examine whether ecological habitat assessments, endangered species historical occurrence data, and restoration research can be used to develop evidence-based strategy for retiring and restoring agricultural lands.

The San Joaquin Desert (SJD) of California is a prominent example because it experienced an extensive conversion to agriculture. Now, new groundwater regulations will lead to retirement on large areas of agricultural lands over the next 20 years. This presents an opportunity to not only restore some of these lands but also explore the challenges associated with balancing direct human needs with other ecosystem-level functions. California is thus an ideal case study for globally rethinking context-specific, single-case study solutions. We used a systematic review and synthesis to address the following three main questions for habitat recovery of endangered species in the SJD.

(1) What are the habitat requirements for key endangered animal species in the region?

(2) Is there historical evidence to support an assessment of suitable habitats for these species?

(3) What restoration techniques apply to these species?

Using the Web of Science and other resources, we reviewed over 1000 independent studies on this topic, refined the evidence, and selected a total of 266 relevant publications. Habitat requirements for each species were described, but there was a critical need to examine quantitative thresholds for these factors to better evaluate habitat suitability of retired lands. There was sufficient evidence of historical vegetation to model suitable habitats and design the physical restoration of retired lands. Direct interventions associated with restoration strategies have been infrequently tested. Sparse and diverse evidence associated with direct experimental manipulations is not uncommon in applied ecology, and synthesis is an excellent tool for highlighting these gaps for future research to examine. This review suggests that retired agricultural land is a viable asset for threatened and endangered species, but to effectively advance restoration research and management, direct tests of restoration techniques and an assessment of relative costs for interventions are needed for a given region.

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California Aqueduct Subsidence Study
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California Aqueduct Subsidence Study
Department of Water Resources | June 1, 2017...
Summary
In 2006, the San Luis Field Division of the California Department of Water Resources' Division of Operations and Maintenance (O&M) began to see...
In 2006, the San Luis Field Division of the California Department of Water Resources' Division of Operations and Maintenance (O&M) began to see a reduction in flow capacity through the California Aqueduct (Aqueduct) Pools 20 and 21. Subsidence had lowered portions of the Aqueduct and caused the concrete liner freeboard (the vertical distance between the water surface and the top of the concrete liner) to be reduced from its normal of 3 feet, to less than 1 foot. Subsidence had also decreased the ability to store water in those pools, which is normally done to add operational flexibility and to manage pumping at the Aqueduct’s pumping plants.

While subsidence has reduced the amount of freeboard and flow capacity at specific locations, contracted deliveries have not been curtailed through 2016. Additional work, to be addressed in the next phase of the project, will quantify how hydraulic limitations have impacted operations and will estimate future impacts to deliveries, based on forecasted subsidence rates.

The purpose of this project is to research and study past and present subsidence reports and data, and to understand and summarize the magnitude, location, and effects on the Aqueduct. This report summarizes the significant information found, and presents the results of the data that were analyzed.

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California Water Plan 2013: Tulare Lake Hydrologic Region Report
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California Water Plan 2013: Tulare Lake Hydrologic Region Report
Department of Water Resources | October 30, 2014...
Summary
While the Tulare Lake Hydrologic Region (Tulare Lake region) remains the largest agricultural region in California with irrigated acreage declining only slightly from...
While the Tulare Lake Hydrologic Region (Tulare Lake region) remains the largest agricultural region in California with irrigated acreage declining only slightly from 2005 to 2010, it is facing many issues. The 2007-2009 drought along with reduced imported surface water supplies from the Delta, led to increased groundwater pumping. Older water storage and delivery facilities are affecting flood management and distribution reliability. Along with more agricultural reliance on groundwater, many smaller communities have to deal with aging municipal wells and sewage treatment facilities that have difficulty meeting water quality standards.

Additionally, the urban population continues to grow, gaining 8 percent from 2005 to 2010. However, most of the region’s agricultural, urban including disadvantaged communities (DACs), environmental, and other interests are realizing that integrated water management (IWM) strategies are the most effective way to deal with these challenges.

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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 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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Data from Exploratory Sampling of Groundwater in Selected Oil and Gas Areas of Coastal Los Angeles County and Kern and Kings Counties in Southern San Joaquin Valley, 2014–15
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Data from Exploratory Sampling of Groundwater in Selected Oil and Gas Areas of Coastal Los Angeles County and Kern and Kings Counties in Southern San Joaquin Valley, 2014–15
USGS | January 1, 1970...
Summary
Exploratory sampling of groundwater in coastal Los Angeles County and Kern and Kings Counties of the southern San Joaquin Valley was done by...
Exploratory sampling of groundwater in coastal Los Angeles County and Kern and Kings Counties of the southern San Joaquin Valley was done by the U.S. Geological Survey from September 2014 through January 2015 as part of the California State Water Resources Control Board’s Water Quality in Areas of Oil and Gas Production Regional Groundwater Monitoring Program. The Regional Groundwater Monitoring Program was established in response to the California Senate Bill 4 of 2013 mandating that the California State Water Resources Control Board design and implement a groundwater-monitoring program to assess potential effects of well-stimulation treatments on groundwater resources in California. The U.S. Geological Survey is in cooperation with the California State Water Resources Control Board to collaboratively implement the Regional Groundwater Monitoring Program through the California Oil, Gas, and Groundwater Project.

Many researchers have documented the utility of different suites of chemical tracers for evaluating the effects of oil and gas development on groundwater quality. The purpose of this exploratory sampling effort was to determine whether tracers reported in the literature could be used effectively in California. This reconnaissance effort was not designed to assess the effects of oil and gas on groundwater quality in the sampled areas. A suite of water-quality indicators and geochemical tracers were sampled at groundwater sites in selected areas that have extensive oil and gas development. Groundwater samples were collected from a total of 51 wells, including 37 monitoring wells at 17 multiple-well monitoring sites in coastal Los Angeles County and 5 monitoring wells and 9 water-production wells in southern San Joaquin Valley, primarily in Kern and Kings Counties.

Groundwater samples were analyzed for field water-quality indicators; organic constituents, including volatile and semi-volatile organic compounds and dissolved organic carbon indicators; naturally present inorganic constituents, including trace elements, nutrients, major and minor ions, and iron species; naturally present stable and radioactive isotopes; dissolved noble gases; dissolved standard and hydrocarbon gases, ?13C of methane, ethane, and ?2H of methane. In total, 249 constituents and water-quality indicators were measured.
Four types of quality-control samples (blanks, replicates, matrix spikes, and surrogates spiked in environmental and blank samples) were collected at approximately 10 percent of the wells. The quality-control data were used to determine whether the groundwater-sample data were of sufficient quality for the measured analytes to be used as potential indicators of oil and gas effects. The data from the 51 groundwater samples and from the quality-control samples are presented in this report.

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Desalination Demonstration Report for Buena Vista Water Storage District
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Desalination Demonstration Report for Buena Vista Water Storage District
Buena Vista Water Storage District | December 1, 2003...
Summary
Saline agricultural drainage water within the Buena Vista Water Storage District is accumulating in shallow aquifers located below productive farmland. This saline water...
Saline agricultural drainage water within the Buena Vista Water Storage District is accumulating in shallow aquifers located below productive farmland. This saline water has risen to elevations where it increases the soil salinity in crop root zones resulting in reduced crop productivity and in some areas of the District, lands have been taken out of production because of the high saline groundwater table.

A reverse osmosis pilot plant was constructed to demonstrate the feasibility of desalting saline irrigation drainage water for use as a water supply for agricultural or municipal use. The demonstration plant was constructed in the Buena Vista Water Storage District northwest of Bakersfield, California. The plant operated during the irrigation seasons of 2000 and 2002.

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

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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), Central Valley Regional Water Quality Control Board | July 27, 2018...
Summary
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...
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.

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Dry groundwater wells in the western United States
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Dry groundwater wells in the western United States
Environmental Research Letters | July 28, 2017...
Summary
Declining groundwater levels are common in parts of the western US, but their impact on the ability of wells to pump groundwater is...
Declining groundwater levels are common in parts of the western US, but their impact on the ability of wells to pump groundwater is not known. Here we collate groundwater well records for the western United States and present the recorded locations, depths, and purposes of more than two million groundwater wells constructed between 1950 and 2015. We then use the well records to estimate the percentage of wells that were dry during the years 2013–2015. During the two-year period, dry wells were concentrated in rural areas with high agricultural productivity, such as parts of the California Central Valley and the High Plains. Our results support anecdotal evidence that wells used for domestic purposes are more susceptible to drying than wells used for agricultural purposes throughout California’s Central Valley because the former tend to be shallower. However, this is not the case in all regions. Our findings suggest that declining groundwater levels are threatening drinking water reliability and agricultural productivity, and consequently, have key implications for both domestic and agricultural water security. Ongoing reductions to groundwater storage are drying groundwater wells in the western US, and this manifestation of water scarcity warrants innovative groundwater management transcending status quos.

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Economic and Water Supply Effects of Ending Groundwater Overdraft in California’s Central Valley
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Economic and Water Supply Effects of Ending Groundwater Overdraft in California’s Central Valley
San Francisco Estuary and Watershed Science | March 1, 2016...
Summary
Surface water and groundwater management are often tightly linked, even when linkage is not intended or expected. This link is especially common in...
Surface water and groundwater management are often tightly linked, even when linkage is not intended or expected. This link is especially common in semi-arid regions, such as California. This paper summarizes a modeling study on the effects of ending long-term overdraft in California’s Central Valley, the state’s largest aquifer system. The study focuses on economic and operational aspects, such as surface water pumping and diversions, groundwater recharge, water scarcity, and the associated operating and water scarcity costs. This analysis uses CALVIN, a hydro-economic optimization model for California’s water resource system that suggests operational changes to minimize net system costs for a given set of conditions, such as ending long-term overdraft. Based on model results, ending overdraft might induce some major statewide operational changes, including large increases to Delta exports, more intensive conjunctive-use operations with increasing artificial and in-lieu recharge, and greater water scarcity for Central Valley agriculture. The statewide costs of ending roughly 1.2 maf yr of groundwater overdraft are at least $50 million per year from additional direct water shortage and additional operating costs. At its worst, the costs of ending Central Valley overdraft could be much higher, perhaps comparable to the recent economic effects of drought. Driven by recent state legislation to improve groundwater sustainability, ending groundwater overdraft has important implications statewide for water use and management, particularly in the Sacramento–San Joaquin Delta. Ending Central Valley overdraft will amplify economic pressure to increase Delta water exports rather than reduce them, tying together two of California’s largest water management problems.

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Engineer’s Report for the North Fork Kings Groundwater Sustainability Agency: Proposition 218 Procedures for Benefit Assessments
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Engineer’s Report for the North Fork Kings Groundwater Sustainability Agency: Proposition 218 Procedures for Benefit Assessments
North Fork Kings GSA | January 15, 2018...
Summary
The North Fork Kings Groundwater Sustainability Agency (NFKGSA or Agency) recently formed with the primary purpose of compliance with the Sustainable Groundwater Management...

The North Fork Kings Groundwater Sustainability Agency (NFKGSA or Agency) recently formed with the primary purpose of compliance with the Sustainable Groundwater Management Act (SGMA). As a Groundwater Sustainability Agency (GSA), the Agency may develop, adopt, and implement a Groundwater Sustainability Plan (GSP) for sustainable management of groundwater for that portion of the Kings Subbasin (Subbasin) underlying the Agency. The newly formed Agency needs to implement an assessment rate structure that is sufficient to fund Agency operations and required activities pursuant to SGMA. The NFKGSA will develop, in coordination with other GSAs in the Kings Subbasin, a GSP that provides for achieving groundwater sustainability in the Kings Subbasin of the San Joaquin Valley Groundwater Basin underlying the Agency by January 2040. SGMA requires that a GSP be submitted to the California Department of Water Resources (DWR) by January 31, 2020 since the Kings Subbasin is considered a high priority, critically overdrafted subbasin.

Based on the Agency’s needs, the NFKGSA Board of Directors is requesting landowner approval to levy assessments to generate sufficient revenue to fund both annual Agency operation costs and expenses associated with the development and implementation of a GSP. The annual operational costs have already begun and are used to fund Agency operations and activities required by SGMA, including retaining consulting firms and legal counsel to provide Agency oversight and lead the Agency through the steps for SGMA compliance. Expenses consist of administrative support, GSP development, and GSP implementation, with GSP development occurring over the next several years and GSA administration and GSP implementation anticipated to be on-going expenses. The administrative annual expenses include an assumed annual 3% inflation factor. The assessments are planned to apply equally to all assessable lands within the Agency’s boundaries.

The Assessment Roll provided in Attachment D identifies the acreage for each assessable parcel according to the 2017 tax rolls of Fresno County and Attachment E identifies the acreage for each assessable parcel according to the 2017 tax rolls of Kings County. The following table provides an example schedule of the proposed assessments during the next five years that are the subject of this Proposition 218 Engineer’s Report. The actual assessment rate will be set annually by the Board, based on the budget needs, but will not exceed the proposed maximum rate. Assessments will continue beyond Fiscal Year 2022-23, but at this time the assessment rate after this initial five-year period is unknown because the GSP Implementation costs will not be fully determined until the GSP is developed. The projects that will be proposed as part of the GSP implementation to attain sustainability and maintain the threshold levels established in the GSP will likely require supplemental funding and assessments greater than the maximum assessments recommended in this report, and approval by the landowners in a future Proposition 218 election will be required.

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Estimates of Natural and Unimpaired Flows for the Central Valley of California: Water Years 1922-2014 (draft)
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Estimates of Natural and Unimpaired Flows for the Central Valley of California: Water Years 1922-2014 (draft)
California Department of Water Resources (DWR) | March 1, 2016...
Summary
Estimating regional water supplies that would have occurred absent human activities is a common practice in water resources planning. In this report, such...

Estimating regional water supplies that would have occurred absent human activities is a common practice in water resources planning. In this report, such theoretical water supply estimates are referred to as “unimpaired” flow. Since 1980, the Department of Water Resources (Department) has periodically published estimates of Central Valley unimpaired flows. In spite of the Department’s previous attempts to distinguish between natural conditions and its calcula tion of theoretical unimpaired flows, unimpaired flow estimates have frequently been used as a surrogate measure of natural conditions, presumably because natural flow estimates were unavailable. A major objective of this report is to clarify the conceptua l differences between natural and unimpaired flows.

In this report, the term “unimpaired” flow is used to describe a theoretically available water supply assuming existing river channel conditions in the absence of (1) storage regulation for water supply a nd hydropower purposes and (2) stream diversions for agricultural and municipal uses. Unimpaired flow estimates are theoretical in that such conditions have not occurred historically. In pristine watersheds which have undergone little land use change, unim paired flow estimates provide a fixed frame of reference to develop relationships between precipitation, runoff, and water supply based on long - term hydrologic records. For many years these relationships were based on the assumption of stationarity, i.e. that the past is a good indicator of the future. However, global warming now requires hydrologists and water resources managers to analyze non-stationary processes, requiring more sophisticated tools and techniques to quantify future water supplies. This report updates and extends the Department’s previous published estimates of unimpaired flows for 24 Central Valley sub-basins and the Delta. Monthly unimpaired flows are presented for water years 1922 - 2014.

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Estimating the permanent loss of groundwater storage in the southern San Joaquin Valley, California
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Estimating the permanent loss of groundwater storage in the southern San Joaquin Valley, California
American Geophysical Union Water Resources Research | February 23, 2017...
Summary
In the San Joaquin Valley, California, recent droughts starting in 2007 have increased the pumping of groundwater, leading to widespread subsidence. In the...
In the San Joaquin Valley, California, recent droughts starting in 2007 have increased the pumping of groundwater, leading to widespread subsidence. In the southern portion of the San Joaquin Valley, vertical subsidence as high as 85 cm has been observed between June 2007 and December 2010 using Interferometric Synthetic Aperture Radar (InSAR). This study seeks to map regions where inelastic (not recoverable) deformation occurred during the study period, resulting in permanent compaction and loss of groundwater storage. We estimated the amount of permanent compaction by incorporating multiple data sets: the total deformation derived from InSAR, estimated skeletal?specific storage and hydraulic parameters, geologic information, and measured water levels during our study period. We used two approaches, one that we consider to provide an estimate of the lowest possible amount of inelastic deformation, and one that provides a more reasonable estimate. These two approaches resulted in a spatial distribution of values for the percentage of the total deformation that was inelastic, with the former estimating a spatially averaged value of 54%, and the latter a spatially averaged value of 98%. The former corresponds to the permanent loss of $urn:x-wiley:00431397:media:wrcr22526:wrcr22526-math-0001$ m³ of groundwater storage, or roughly 5% of the volume of groundwater used over the study time period; the latter corresponds to the loss of $urn:x-wiley:00431397:media:wrcr22526:wrcr22526-math-0002$ m³ of groundwater storage, or roughly 9% of the volume of groundwater used. This study demonstrates that a data-driven approach can be used effectively to estimate the permanent loss of groundwater storage.

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Engineer’s Report for the North Fork Kings Groundwater Sustainability Agency: Proposition 218 Procedures for Benefit Assessments

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Estimates of Natural and Unimpaired Flows for the Central Valley of California: Water Years 1922-2014 (draft)

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Estimating the permanent loss of groundwater storage in the southern San Joaquin Valley, California

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