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2017 Salinas Valley Groundwater Level Contours & Seawater Intrusion Maps
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2017 Salinas Valley Groundwater Level Contours & Seawater Intrusion Maps
Monterey County Water Resources Agency (MCWRA) | April 24, 2018...
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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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A Water Resources Data Network Evaluation for Monterey County, California; Phase 1; South County
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A Water Resources Data Network Evaluation for Monterey County, California; Phase 1; South County
U..S. Geological Survey, Monterey County Flood Control and Water Conservation District | July 12, 1986...
Summary
An evaluation made of rainfall, surface water, groundwater, and water quality monitoring networks in Salinas River basin in southern Monterey County, California, proposed...
An evaluation made of rainfall, surface water, groundwater, and water quality monitoring networks in Salinas River basin in southern Monterey County, California, proposed all long-term rain gages be continued for extending short-term records and suggested the installation of two additional recording gages. Eight new storage rain gages were suggested at midaltitudes of east and west sides of Salinas Valley where few data are available. The evaluation revealed some short-term gaging stations could be discontinued because of good regression relations between them and the long-term stations Arroyo Seco near Soledad.

Of 16 stations selected for the proposed network, 4 are new recording stations, 6 are new nonrecording streamflow and water quality sampling sites, 5 are existing stations, and the last is a station operated from 1969 to 1976; also included are water quality sampling stations on Lakes Nacimiento and San Antonio. The proposed groundwater network was developed from information on geology, geohydrology, and groundwater quality, high priority objectives for groundwater network, and consideration for providing good areal coverage of levels and water quality. Of 145 sites selected, 86 are existing monitoring wells.

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A Water Resources Data Network Evaluation for Monterey County, California; Phase 3, Northern Salinas River Drainage Basin
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A Water Resources Data Network Evaluation for Monterey County, California; Phase 3, Northern Salinas River Drainage Basin
U.S. Geological Survey, Monterey County Flood Control and Water Conservation District | December 13, 1990...
Summary
Continuing data collection and analysis are vital to efficient development and management of water resources. To insure that water managers have adequate information...
Continuing data collection and analysis are vital to efficient development and management of water resources. To insure that water managers have adequate information on conditions and trends, data-collection programs must be evaluated and updated periodically. Changes in population, land use, and agricultural practices may increase the demand for water, so that effective water management and supporting data collection become even more critical. Consideration of cost effectiveness, however, means that every site must count, and redundancy must be minimized. Water resources management and monitoring are ever-changing, and periodic reevaluation is a necessary part of this process. This report presents an evaluation of precipitation, surface-water, and ground-water monitoring networks in the northern Salinas River drainage basin of Monterey County, California. This report is third in a series of reports prepared in cooperation with the Monterey County Flood Control and Water Conservation District (MCFCWCD). The phase 1 report (Showalter and Hoffard, 1986) covers the southern Salinas River drainage basin, the phase 2 report covers the north county and coastal areas of Monterey County (W.E. Templin, P.E. Smith, and R.C. Schluter, U.S. Geological Survey, written commun., 1989), and this report (phase 3) covers the northern Salinas River drainage basin.

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Alamitos Barrier Project: Annual Report on the Control of Seawater Intrusion 2016-2017
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Alamitos Barrier Project: Annual Report on the Control of Seawater Intrusion 2016-2017
Los Angeles County Department of Public Works | June 30, 2017...
Summary
The Alamitos Barrier Project (ABP) was designed and constructed to protect the groundwater supplies of the Central/Orange County Basin of the Coastal Plain...

The Alamitos Barrier Project (ABP) was designed and constructed to protect the groundwater supplies of the Central/Orange County Basin of the Coastal Plain from the intrusion of seawater through the Alamitos Gap area. The project facilities are located near the Los Angeles-Orange County border about two miles inland from the terminus of the San Gabriel River. The original facilities included injection wells to form a freshwater pressure ridge and extraction wells to form a saltwater trough. The freshwater pressure ridge has proven to be historically effective, whereas the saltwater trough has not. As a result, the extraction wells are currently not in operation. A map showing the supply pipeline, injection wells, extraction wells, and observation wells is shown on page A-12.1. The County of Los Angeles Department of Public Works (Public Works) operates and maintains the ABP and its associated facilities under the direction and approval of the Joint Management Committee (JMC), acting on behalf of the Los Angeles County Flood Control District (LACFCD) and the Orange County Water District (OCWD). This report summarizes design and construction issues, operation and maintenance activities, hydrogeologic effects, chloride concentrations, and project costs for Fiscal Year (FY) 2016-17 (i.e., July 1, 2016 through June 30, 2017).

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Analysis and simulation of regional subsidence accompanying groundwater abstraction and compaction of susceptible aquifer systems in the USA

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Analysis and simulation of regional subsidence accompanying groundwater abstraction and compaction of susceptible aquifer systems in the USA
Boletín de la Sociedad Geológica Mexicana | January 17, 2013...
Summary
Regional aquifer-system compaction and land subsidence accompanying groundwater abstraction in susceptible aquifer systems in the USA is a challenge for managing groundwater resources...
Regional aquifer-system compaction and land subsidence accompanying groundwater abstraction in susceptible aquifer systems in the USA is a challenge for managing groundwater resources and mitigating associated hazards. Developments in the assessment of regional subsidence provide more information to constrain analyses and simulation of aquifer-system compaction. Current popular approaches to simulating vertical aquifer-system deformation (compaction), such as those embodied in the aquitard drainage model and the MODFLOW subsidence packages, have proven useful from the perspective of regional groundwater resources assessment. However, these approaches inadequately address related local-scale hazards—ground ruptures and damages to engineered structures on the land surface arising from tensional stresses and strains accompanying groundwater abstraction. This paper presents a brief overview of the general approaches taken by the U.S. Geological Survey toward understanding aquifer-system compaction and subsidence with regard to a) identifying the affected aquifer systems; b) making regional assessments; c) analyzing the governing processes; and d) simulating historical and future groundwater flow and subsidence conditions. Limitations and shortcomings of these approaches, as well as future challenges also are discussed

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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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Bulletin No. 52-B Salinas Basin Investigation Summary Report
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Bulletin No. 52-B Salinas Basin Investigation Summary Report
California Department of Water Resources, formerly State Department of Public Works Division of Water Resources | December 13, 1946...
Summary
The Board of Supervisors and the Flood Control and Water Conservation Conmittee of the County of Monterey became concerned in April 1944 over...
The Board of Supervisors and the Flood Control and Water Conservation Conmittee of the County of Monterey became concerned in April 1944 over the intrusion of saline water in the ground water supply utilized for irrigation, domestic and industrial purposes in the lower reaches of the Salinas Basin near Monterey Bay. The entire agricultural and urban development in the basin depends on an adequate supply of ground water of good quality.

There had been some abandonment of wells in the Salinas Basin near the bay shore due to excessive salinity as early as 1938. Accelerated encroachment of the contamination occurred in 1943, and the matter was brought to public attention in 1944. The County of Monterey and the Department of Public Works, State of California, executed a contract on July 10, 1944, providing for maintenance in cooperation an investigation of the water resources of the Salinas Valley in Monterey County and conditions relative thereto which obtain in the valley or affect the water supplies available therefor. It further provides that the Department shall prepare a report based on the investigation setting forth the physical facts pertinent to water supply and to salt water Intrusion, and if possible, incorporate findings as to a method or methods of solving the problems involved.

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California Groundwater Units
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California Groundwater Units
U.S. Geological Survey (USGS) | June 5, 2014...
Summary
The California Groundwater Units dataset classifies and delineates areas within the State of California into one of three groundwater-based polygon units: (1) those...
The California Groundwater Units dataset classifies and delineates areas within the State of California into one of three groundwater-based polygon units: (1) those areas previously defined as alluvial groundwater basins or subbasins, (2) highland areas that are adjacent to and topographically upgradient of groundwater basins, and (3) highland areas not associated with a groundwater basin, only a hydrogeologic province.

In total, 938 Groundwater Units are represented. The Groundwater Units dataset relates existing groundwater basins with their newly delineated highland areas which can be used in subsequent hydrologic studies. The methods used to delineate groundwater-basin-associated highland areas are similar to those used to delineate a contributing area (such as for a lake or water body); the difference is that highland areas are constrained to the immediately surrounding upslope (upstream) area. Upslope basins have their own delineated highland.

A geoprocessing tool was created to facilitate delineation of highland areas for groundwater basins and subbasins and is available for download.

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California Statewide Groundwater Elevation Monitoring (CASGEM) Status Report 2012
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California Statewide Groundwater Elevation Monitoring (CASGEM) Status Report 2012
California Department of Water Resources (DWR) | April 23, 2012...
Summary
Senate Bill X7 6 (SBX7 6) (Chapter 1, Statutes 2009) added provisions for Groundwater Monitoring to Division 6 of the Water Code (Water...
Senate Bill X7 6 (SBX7 6) (Chapter 1, Statutes 2009) added provisions for Groundwater Monitoring to Division 6 of the Water Code (Water Code § 10920 et seq.), and authorizes the Department of Water Resources (DWR) to establish permanent, locally managed, groundwater-elevation monitoring and reporting in all of California's 515 alluvial groundwater basins.

To implement SBX7 6, DWR developed the California Statewide Groundwater Elevation Monitoring (CASGEM) program. SBX7 6 requires DWR to report to the Governor and the Legislature by January 1, 2012, and thereafter in years ending in "5" or "0" regarding the findings of this program.

The purpose of CASGEM is to establish a program of regular and systematic monitoring of groundwater elevations and to track seasonal and long-term trends in groundwater elevations statewide. The law directs DWR to rely and build upon the many established, local, long-term groundwater monitoring and management programs conducted by local entities throughout the state. DWR's role is to coordinate the CASGEM program, to work cooperatively with local entities, and to maintain the submitted groundwater elevation data in a manner that is readily and widely available to the public. Collection and evaluation of groundwater elevation data throughout the state is an important fundamental step toward improving management of California's groundwater resources.

Within the first two years of program development, DWR has met the requirements specified in SBX7 6 to establish a statewide groundwater elevation monitoring and reporting program by January 1, 2012.

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California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013
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California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013
California Department of Water Resources (DWR) | April 1, 2015...
Summary
The primary goal of California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013 (California’s Groundwater Update 2013)...
The primary goal of California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013 (California’s Groundwater Update 2013) is to provide foundational information to improve the statewide and regional understanding of groundwater conditions and management programs. The set of data, information, and analyses developed by the California Department of Water Resources (DWR) will help set the stage for future Bulletin 118 and California Water Plan updates, and help local and regional agencies plan for sustainable groundwater management by providing an on-going reporting of essential groundwater data, information, and analyses.

A second goal is to identify data gaps and groundwater management challenges that are meant to serve as a guidepost for prioritizing future groundwater data collection and funding opportunities. The final goal is to develop a set of recommendations to improve groundwater management in California.

Findings, data gaps, and recommendations were developed for the state as a whole and for each of the 10 hydrologic regions. Statewide findings, data gaps, and recommendations presented herein serve as a summary of those commonly identified at the regional level.

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Coupling a spatiotemporally distributed soil water budget with stream‐depletion functions to inform stakeholder‐driven management of groundwater‐dependent ecosystems

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Coupling a spatiotemporally distributed soil water budget with stream‐depletion functions to inform stakeholder‐driven management of groundwater‐dependent ecosystems
American Geophysical Union (AGU) | November 12, 2013...
Summary
Groundwater pumping, even if only seasonal, may significantly impact groundwater‐dependent ecosystems through increased streamflow depletion, particularly in semiarid and arid regions. The effects...
Groundwater pumping, even if only seasonal, may significantly impact groundwater‐dependent ecosystems through increased streamflow depletion, particularly in semiarid and arid regions. The effects are exacerbated, under some conditions, by climate change. In social sciences, the management of groundwater‐dependent ecosystems is generally considered a “wicked” problem due to the complexity of affected stakeholder groups, disconnected legal frameworks, and a divergence of policies and science at the cross road between groundwater and surface water, and between ecosystems and water quality. A range of often simplified scientific tools plays an important role in addressing such problems. Here we develop a spatiotemporally distributed soil water budget model that we couple with an analytical model for stream depletion from groundwater pumping to rapidly assess seasonal impacts of groundwater pumping on streamflow during critical low flow periods. We demonstrate the applicability of the tool for the Scott Valley in Northern California, where protected salmon depend on summer streamflow fed by cool groundwater. In this example, simulations suggest that increased recharge in the period immediately preceding the critical low streamflow season, and transfer of groundwater pumping away from the stream are potentially promising tools to address ecosystem concerns, albeit raising difficult infrastructure and water trading issues. In contrast, additional winter recharge at the expense of later spring recharge, whether intentional or driven by climate may reduce summer streamflows. Comparison to existing detailed numerical groundwater model results suggests that the coupled soil water mass balance—stream depletion function approach provides a viable tool for scenario development among stakeholders, to constructively inform the search for potential solutions, and to direct more detailed, complex site‐specific feasibility studies. The tool also identifies important field monitoring efforts needed to improve the understanding and quantification of site‐specific groundwater‐stream interactions.

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Data from a Thick Unsaturated Zone Underlying Oro Grande and Sheep Creek Washes in the Western Part of the Mojave Desert, near Victorville, San Bernardino County, California

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Data from a Thick Unsaturated Zone Underlying Oro Grande and Sheep Creek Washes in the Western Part of the Mojave Desert, near Victorville, San Bernardino County, California
U.S. Geological Survey | January 1, 2000...
Summary
This report presents data collected as part of a cooperative study of infiltration and groundwater recharge to the regional aquifer near Victorville, California....

This report presents data collected as part of a cooperative study of infiltration and groundwater recharge to the regional aquifer near Victorville, California. The study was funded by the U.S. Geological Survey (USGS) and the Mojave Water Agency. This report contains data on drilling, instrument installation, the physical properties of unsaturated earth materials, and the chemical and isotopic composition of leachate from cores and cuttings, soil water, and soil gas collected at sites underlying Oro Grande and Sheep Creek Washes in the Mojave Desert. The report also presents similar data collected at sites on the alluvial fan near these washes and at a site near Cajon Pass. The sites on the alluvial fan and near Cajon Pass served as controls for the study and allow for comparison with data from previous studies. In addition, the report presents data on the chemical and isotopic composition of bulk precipitation, and on groundwater levels and quality. Interpretation of these data is beyond the scope of this report.

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Depletion Requiremements in California’s Sustainable Groundwater Management Act
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Depletion Requiremements in California’s Sustainable Groundwater Management Act
Environmental Defense Fund | May 17, 2018...
Summary
Successful implementation of the Sustainable Groundwater Management Act (SGMA), including its provision to avoid signicant and unreasonable depletion of interconnected surface water, is...

Successful implementation of the Sustainable Groundwater Management Act (SGMA), including its provision to avoid signicant and unreasonable depletion of interconnected surface water, is a high priority for the Environmental Defense Fund (EDF). The lack of established mechanisms for addressing depletions of interconnected surface water makes the implementation of this aspect of SGMA especially challenging. Accordingly, EDF offers recommendations to address the requirements of the law related to depletion of interconnected surface water, commonly referred to as “Undesirable Result No. 6” (UR #6). We believe that our proposed approach provides a reasonable balance among the con icting factors of rigor, cost, uncertainty, and enforceability that weigh on the implementation of this requirement. Our goal is to offer a pathway to achieve the fundamental and critical objective of UR#6 – preventing signi cant impacts to water users and ecosystems—in a way that is not unreasonably costly or unproductively burdensome on the Groundwater Sustainability Agencies (GSAs), water users, and state agencies who will bear most of the burden of complying with—or ensuring compliance with—SGMA.

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Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California

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Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California
Water Resources Research, U.S. Geological Survey (USGS) | April 15, 1998...
Summary
Interferometric synthetic aperture radar (InSAR) has great potential to detect and quantify land subsidence caused by aquifer system compaction. InSAR maps with high...

Interferometric synthetic aperture radar (InSAR) has great potential to detect and quantify land subsidence caused by aquifer system compaction. InSAR maps with high spatial detail and resolution of range displacement (10 mm in change of land surface elevation) were developed for a groundwater basin (103 km2) in Antelope Valley, California, using radar data collected from the ERS-1 satellite. These data allow comprehensive comparison between recent (1993–1995) subsidence patterns and those detected historically (1926–1992) by more traditional methods. The changed subsidence patterns are generally compatible with recent shifts in land and water use. The InSAR-detected patterns are generally consistent with predictions based on a coupled model of groundwater flow and aquifer system compaction. The minor inconsistencies may reflect our imperfect knowledge of the distribution and properties of compressible sediments. When used in conjunction with coincident measurements of groundwater levels and other geologic information, InSAR data may be useful for constraining parameter estimates in simulations of aquifer system compaction.

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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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Effects of Groundwater Pumping on Agricultural Drains in the Tule Lake Subbasin, Oregon and California
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Effects of Groundwater Pumping on Agricultural Drains in the Tule Lake Subbasin, Oregon and California
U.S. Geological Survey, U.S. Fish and Wildlife Service, U.S. Bureau of Reclamation | July 24, 2015...
Summary
Since 2001, irrigators in the upper Klamath Basin have increasingly turned to groundwater to compensate for reductions in surface-water allocation caused by shifts...

Since 2001, irrigators in the upper Klamath Basin have increasingly turned to groundwater to compensate for reductions in surface-water allocation caused by shifts from irrigation use to instream flows for Endangered Species Act listed fishes. The largest increase in groundwater pumping has been in and around the Bureau of Reclamation’s Klamath Irrigation Project, which includes the Tule Lake subbasin in the southern part of the upper Klamath Basin. Agricultural drains on the Klamath Project are an important source of water for downstream irrigators and for the Tule Lake and Lower Klamath Lake National Wildlife Refuges. U.S. Geological Survey regional groundwater-flow model simulations and records of irrigation-return flow pumped from the Tule Lake subbasin into the adjacent Lower Klamath Lake subbasin have indicated that water-level declines from pumping may be causing decreased flow of shallow groundwater to agricultural drains.

To better define the effect of increased pumping on drain flow and on the water balance of the groundwater system, the annual water volume pumped from drains in three subareas of the Tule Lake subbasin was estimated and a fine-grid, local groundwater model of the Tule Lake subbasin was constructed. Results of the agricultural-drain flow analysis indicate that groundwater discharge to drains has decreased such that flows in 2012 were approximately 32,400 acre-ft less than the 1997–2000 average flow. This decrease was concentrated in the northern and southeastern parts of the subbasin, which corresponds with the areas of greatest groundwater pumping. Model simulation results of the Tule Lake subbasin groundwater model indicate that increased supplemental pumping is the dominant stress to the groundwater system in the subbasin. Simulated supplemental pumping and decreased recharge from irrigation between 2000 and 2010 totaled 323,573 acre-ft, 234,800 acre-ft (73 percent) of which was from supplemental pumping. The response of the groundwater system to this change in stress included about 180,500 acre-ft (56 percent) of decreased groundwater discharge to drains and a 126,000 acre-ft (39 percent) reduction in aquifer storage. The remaining 5 percent came from reduced groundwater flow to other model boundaries, including the Lost River, the Tule Lake sumps, and interbasin flow.

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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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Evaluation of a Ground-Water Flow and Transport Model of the Upper Coachella Valley, California
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Evaluation of a Ground-Water Flow and Transport Model of the Upper Coachella Valley, California
U.S. Geological Survey; California Regional Water Quality Control Board, Colorado River Basin Region | June 25, 1992...
Summary
A geohydrologic data base was compiled to evaluate the changes in ground-water conditions in the upper Coachella Valley, California, since 1978, when the...
A geohydrologic data base was compiled to evaluate the changes in ground-water conditions in the upper Coachella Valley, California, since 1978, when the results of a previous ground-water-model study were published. The compiled data were analyzed to improve understanding of the ground-water flow system and the effects on water quality of an existing artificial-recharge program. Analysis of well logs indicates that several zones of differing permeability can be correlated throughout the valley. Analysis of the water-quality data suggests that the artificial recharge of Colorado River water has caused increases in dissolved solids in some wells. Sparse data indicate that the recharged water moves much more rapidly through the uppermost part of the ground-water system than through deeper parts. An evaluation of the existing ground-water simulation model of the upper Coachella Valley that was developed in the 1978 study yielded several conclusions. First, the 300- to 400-foot rise in water levels in the artificialrecharge area in 1985-86 significantly affected the groundwater flow system. Transmissivities in the model had to be increased to reflect the increase in saturated thickness. Storage-coefficient values in the model had to be increased from 0.02 (used in the previous study) to 0.10-0.15 to simulate the unconfined water-level response during this period. Second, stream-recharge and underflow rates from San Gorgonio Pass during 1979-86 seem to have been higher than the values estimated for previous studies. Conditions generally were wetter in 1979-86 than during the period in which the earlier estimates were made. Third, the flow system could be simulated more accurately if the model were extended to its true southeastern boundary, the Salton Sea. Finally, there are important vertical differences in transport of the artificially recharged water that the two-dimensional areal transport model cannot simulate.

The study results indicate several additional data collection and modeling needs. The drilling of several sets of monitor wells perforated at different depths could help better define the three-dimensional flow system and waterquality differences. Additional data also are needed on underflow and stream recharge, evaporation rates and infiltration rates at the artificial-recharge facilities, and net pumpage. Three-dimensional flow and transport models are needed to evaluate the effects of ground-water development on water levels and water quality.

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2017 Salinas Valley Groundwater Level Contours & Seawater Intrusion Maps

2017 Salinas Valley Groundwater Level Contours & Seawater Intrusion Maps

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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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A Water Resources Data Network Evaluation for Monterey County, California; Phase 1; South County

A Water Resources Data Network Evaluation for Monterey County, California; Phase 1; South County

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A Water Resources Data Network Evaluation for Monterey County, California; Phase 3, Northern Salinas River Drainage Basin

A Water Resources Data Network Evaluation for Monterey County, California; Phase 3, Northern Salinas River Drainage Basin

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Alamitos Barrier Project: Annual Report on the Control of Seawater Intrusion 2016-2017

Alamitos Barrier Project: Annual Report on the Control of Seawater Intrusion 2016-2017

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Analysis and simulation of regional subsidence accompanying groundwater abstraction and compaction of susceptible aquifer systems in the USA

Analysis and simulation of regional subsidence accompanying groundwater abstraction and compaction of susceptible aquifer systems in the USA

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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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Bulletin No. 52-B Salinas Basin Investigation Summary Report

Bulletin No. 52-B Salinas Basin Investigation Summary Report

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California Groundwater Units

California Groundwater Units

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California Statewide Groundwater Elevation Monitoring (CASGEM) Status Report 2012

California Statewide Groundwater Elevation Monitoring (CASGEM) Status Report 2012

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California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013

California’s Groundwater Update 2013: A Compilation of Enhanced Content for California Water Plan Update 2013

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Coupling a spatiotemporally distributed soil water budget with stream‐depletion functions to inform stakeholder‐driven management of groundwater‐dependent ecosystems

Coupling a spatiotemporally distributed soil water budget with stream‐depletion functions to inform stakeholder‐driven management of groundwater‐dependent ecosystems

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Data from a Thick Unsaturated Zone Underlying Oro Grande and Sheep Creek Washes in the Western Part of the Mojave Desert, near Victorville, San Bernardino County, California

Data from a Thick Unsaturated Zone Underlying Oro Grande and Sheep Creek Washes in the Western Part of the Mojave Desert, near Victorville, San Bernardino County, California

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Depletion Requiremements in California’s Sustainable Groundwater Management Act

Depletion Requiremements in California’s Sustainable Groundwater Management Act

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Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California

Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California

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Dry groundwater wells in the western United States

Dry groundwater wells in the western United States

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Effects of Groundwater Pumping on Agricultural Drains in the Tule Lake Subbasin, Oregon and California

Effects of Groundwater Pumping on Agricultural Drains in the Tule Lake Subbasin, Oregon and California

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

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

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Evaluation of a Ground-Water Flow and Transport Model of the Upper Coachella Valley, California

Evaluation of a Ground-Water Flow and Transport Model of the Upper Coachella Valley, California

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