Depletion and Capture: Revisiting “The Source of Water Derived from Wells”

National Groundwater Association (NGWA) | May 28th, 2014

A natural consequence of groundwater withdrawals is the removal of water from subsurface storage, but the overall rates and magnitude of groundwater depletion and capture

A natural consequence of groundwater withdrawals is the removal of water from subsurface storage, but the overall rates and magnitude of groundwater depletion and capture relative to groundwater withdrawals (extraction or pumpage) have not previously been well characterized. This study assesses the partitioning of long‐term cumulative withdrawal volumes into fractions derived from storage depletion and capture, where capture includes both increases in recharge and decreases in discharge. Numerical simulation of a hypothetical groundwater basin is used to further illustrate some of Theis' (1940) principles, particularly when capture is constrained by insufficient available water. Most prior studies of depletion and capture have assumed that capture is unconstrained through boundary conditions that yield linear responses. Examination of real systems indicates that capture and depletion fractions are highly variable in time and space. For a large sample of long‐developed groundwater systems, the depletion fraction averages about 0.15 and the capture fraction averages about 0.85 based on cumulative volumes. Higher depletion fractions tend to occur in more arid regions, but the variation is high and the correlation coefficient between average annual precipitation and depletion fraction for individual systems is only 0.40. Because 85% of long‐term pumpage is derived from capture in these real systems, capture must be recognized as a critical factor in assessing water budgets, groundwater storage depletion, and sustainability of groundwater development. Most capture translates into streamflow depletion, so it can detrimentally impact ecosystems.

Depletion and response of deep groundwater to climate-induced pumping variability

Nature Portfolio (Springer Nature) | January 23rd, 2017

Groundwater constitutes a critical component of our water resources. Widespread groundwater level declines have occurred in the USA over recent decades, including

Groundwater constitutes a critical component of our water resources. Widespread groundwater level declines have occurred in the USA over recent decades, including in regions not typically considered water stressed, such as areas of the Northwest and mid-Atlantic Coast. This loss of water storage reflects extraction rates that exceed natural recharge and capture. Here, we explore recent changes in the groundwater levels of deep aquifers from wells across the USA, and their relation to indices of interannual to decadal climate variability and to annual precipitation. We show that groundwater level changes correspond to selected global climate variations. Although climate-induced variations of deep aquifer natural recharge are expected to have multi-year time lags, we find that deep groundwater levels respond to climate over timescales of less than one year. In irrigated areas, the annual response to local precipitation in the deepest wells may reflect climate-induced pumping variability. An understanding of how the human response to drought through pumping leads to deep groundwater changes is critical to manage the impacts of interannual to decadal and longer climate variability on the nation’s water resources.

Depletion Requiremements in California’s Sustainable Groundwater Management Act

Environmental Defense Fund (EDF) | May 17th, 2018

Successful implementation of the Sustainable Groundwater Management Act (SGMA), including its provision to avoid signicant and unreasonable depletion of interconn

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.

Depth-dependent seismic sensing of groundwater recovery from the atmospheric-river storms of 2023

American Association for the Advancement of Science (AAAS) | February 13th, 2025

In early 2023, a series of intense atmospheric-river storms eased California’s historic drought, yet the spatiotemporal extent of groundwater recovery remains poorly un

In early 2023, a series of intense atmospheric-river storms eased California’s historic drought, yet the spatiotemporal extent of groundwater recovery remains poorly understood. We tracked two-decadal changes in groundwater in Greater Los Angeles using seismic ambient-field interferometry. The derived seismic hydrographs reveal distinct expressions of groundwater and surficial water droughts: Whereas surface and near-surface water storage nearly fully recovered in the epic wet season of 2023, only about 25% of the groundwater lost since 2006 was restored. On a decadal scale, we find substantial depletion in aquifers below 50-meter depth, with only limited storm-related recovery. Our analysis underscores the need to monitor deep aquifers for a more complete assessment of total water deficits, using high-resolution tools such as seismic sensing. Click here for a plain language summary of this research from the Stanford press office.

Designing Effective Groundwater Sustainability Agencies: Criteria for Evaluation of Local Governance Options

Center for Law, Energy, and the Environment (CLEE) | ?

With the passage of the Sustainable Groundwater Management Act (SGMA)1 in 2014, California took a historic step towards managing the state’s groundwater resources. SGMA

With the passage of the Sustainable Groundwater Management Act (SGMA)1 in 2014, California took a historic step towards managing the state’s groundwater resources. SGMA adopts a state policy of managing groundwater resources “sustainably for long-term reliability and multiple economic, social, and environmental benefits for current and future beneficial uses.”2 Although these ambitious goals are critical to California’s future water security and sustainablility, major questions remain about how to achieve them. Designing institutions for sustainable groundwater management is one of the most pressing challenges for SGMA implementation. Local entities in mediumand high-priority basins must establish Groundwater Sustainability Agencies (GSAs) by June 2017. GSA design and structure will play a critical role in meeting the sustainability goals required by SGMA. Because designing new institutions for good governance is not easy, the need for information and guidance is acute. SGMA leaves great latitude for local decision making. Primary responsibility for groundwater governance lies with GSAs, to be established by local entities in groundwater basins or sub-basins. SGMA does not specify the details for institutional design of GSAs, nor what specific governance actions must be taken to achieve sustainable groundwater management. Instead, the legislation provides an array of regulatory and non-regulatory tools—mostly optional—from which GSAs can choose. Those tools, in addition to existing authorities already available to local agencies, will provide the basis for groundwater governance in each basin. The relatively short timeline for GSA formation requires local governments and other stakeholders to analyze available options and decide, quickly, how to form novel agencies. These agencies should be armed with the tools necessary to meet current and future groundwater challenges. While no governance solution is ever perfect, GSAs will have a greater chance of governing fairly and effectively if their design anticipates some common challenges of shared resource governance. The primary purpose of this document is to assist stakeholders and decision makers in evaluating the design of GSAs. It aims to empower them to think critically about whether proposed GSAs will meet their needs now and in the future, and—if not—which tools may help to achieve these goals. The framework presented here draws on experience in other natural resource management contexts and on research on governance and institutional design to provide lessons learned and illustrative examples.

Detection and Measurement of Land Subsidence and Uplift Using Global Positioning System Surveys and Interferometric Synthetic Aperture Radar, Coachella Valley, California, 2010–17

U.S. Geological Survey (USGS) | September 3rd, 2020

Groundwater has been a major source of agricultural, recreational, municipal, and domestic supply in the Coachella Valley of California since the early 1920s. Pumpi

Groundwater has been a major source of agricultural, recreational, municipal, and domestic supply in the Coachella Valley of California since the early 1920s. Pumping of groundwater resulted in groundwater-level declines as large as 50 feet (ft) or 15 meters (m) by the late 1940s. Because of concerns that the declines could cause land subsidence, the Coachella Valley Water District (CVWD) and the U.S. Geological Survey (USGS) have cooperatively investigated subsidence in the Coachella Valley since 1996. Importation of Colorado River water to the southern Coachella Valley began in 1949, resulting in a reduction in groundwater pumping and a recovery of groundwater levels during the 1950s through the 1970s. Since the late 1970s, the demand for water in the valley increased to the point that groundwater levels again declined in response to increased pumping and, consequently, increased the potential for land subsidence caused by aquifer-system compaction. Several management actions to increase recharge or to reduce reliance on groundwater have been implemented since as early as 1973 to address overdraft in the Coachella Valley. The implementation of three particular projects has markedly improved groundwater conditions in some of the historically most overdrafted areas of the valley: (1) groundwater substitution with surface-water imports since 2006 using Colorado River water through the Mid-Valley Pipeline project, which was expanded through 2017; (2) budget-based, tiered rates since 2009; and (3) managed aquifer recharge at the Thomas E. Levy Groundwater Replenishment Facility since 2009. Global Positioning System (GPS) surveying and interferometric synthetic aperture radar (InSAR) methods were used to determine the location, extent, and magnitude of the vertical land-surface changes in the Coachella Valley during 2010–17, updating 1993–2010 information presented in previous USGS reports. The GPS measurements taken at 24 geodetic monuments in August 2010 and September 2015 indicated that the land-surface elevation was stable at 17 monuments but changed at seven monuments during the 5-year period. Subsidence ranged from 0.17 to 0.43 ±0.09 ft (52 to 132 ±28 millimeters, or mm) at three monuments, and uplift ranged from 0.11 to 0.18 ±0.09 ft (33 to 54 ±28 mm) at four monuments between 2010 and 2015. At two of the monuments that subsided, the subsidence rates decreased between 2010 and 2015 from those computed between 2005 and 2010. Data prior to 2010 were not available for the third monument that subsided; thus, the 2010–15 subsidence rate could not be compared to an earlier period. At three of the monuments that uplifted between 2010 and 2015, data collected in 2005 and 2010 indicated stability. Data prior to 2010 were not available for the fourth monument that uplifted; thus, the 2010–15 uplift rate could not be compared to an earlier period. InSAR analyses for December 28, 2014–June 27, 2017, indicated that the land surface uplifted as much as about 0.20 ft (60 mm) near the Whitewater River Groundwater Replenishment Facility in the northern Coachella Valley and subsided as much as about 0.26 ft (80 mm) in the La Quinta area and less in Palm Desert, Indian Wells, and other localized areas in the southern Coachella Valley. These areas were identified as subsidence areas in previous reports covering periods during 1993–2010. The comparison of 2014–17 subsidence rates with those derived for 1995–2010 generally indicated a substantial slowing of subsidence, however. Analyses of deformation in the northern Coachella Valley were not included in the previous reports, so a comparison to deformation during the earlier period could not be made. Water levels in wells near the subsiding geodetic monuments, in and near the three subsiding areas shown by InSAR, and throughout the valley generally indicated seasonal fluctuations and longer-term stability or rising groundwater levels since about 2010. These results mark a reversal in trends of groundwater-level declines during the preceding decades. This trend reversal provides new insights into aquifer-system mechanics. Although many areas have stopped subsiding, and a few have even uplifted, the few areas that did subside during 2010–17—albeit at a slower rate—indicate a mixed aquifer-system response. Subsidence when groundwater levels are stable or recovering indicates that residual compaction may have occurred. At the same time, coarse-grained materials and thin aquitards may have expanded as groundwater levels recovered. The continued valley-wide stabilization and recovery of groundwater levels since 2010 likely is a result of various projects designed to increase recharge or to reduce reliance on groundwater.

Detection and measurement of land subsidence and uplift using interferometric synthetic aperture radar, San Diego, California, USA, 2016–2018

International Association of Hydrological Sciences (IAHS) | April 22nd, 2020

Land subsidence associated with groundwater-level declines is stipulated as an “undesirable effect” in California’s Sustainable Groundwater Management Act (SGMA), a

Land subsidence associated with groundwater-level declines is stipulated as an “undesirable effect” in California’s Sustainable Groundwater Management Act (SGMA), and has been identified as a potential issue in San Diego, California, USA. The United States Geological Survey (USGS), the Sweetwater Authority, and the City of San Diego, undertook a cooperative study to better understand the hydromechanical response of the coastal aquifer system using Interferometric Synthetic Aperture Radar (InSAR) techniques. Three periods of interest were analyzed for this study that correspond to the periods before and after two substantial changes were made to the location and volume of pumpage: (1) April–August 2016 when groundwater levels and land surface elevation were relatively stable during normal pumping, (2) September 2016–May 2017 when groundwater levels recovered and the land surface uplifted during a period of substantially reduced pumping, (3) June 2017–October 2018 when groundwater levels declined and land subsidence occurred when pumpage resumed and expanded to new wells. Spatial and temporal characterization of the hydromechanical response to changes in pumpage is important for managing land subsidence. Further study using InSAR techniques, especially when combined with ground-based geodetic and monitoring-well networks, will provide water managers information to help effectively manage groundwater resources as stipulated in the SGMA.

Detection and Measurement of Land Subsidence Using Global Positioning System Surveying and Interferometric Synthetic Aperture Radar, Coachella Valley, California, 1996–2005

U.S. Geological Survey (USGS) | June 13th, 2013

Land subsidence associated with ground-water-level declines has been investigated by the U.S. Geological Survey in the Coachella Valley, California, since 1996. G

Land subsidence associated with ground-water-level declines has been investigated by the U.S. Geological Survey in the Coachella Valley, California, since 1996. Groundwater has been a major source of agricultural, municipal, and domestic supply in the valley since the early 1920s. Pumping of ground water resulted in water-level declines as large as 15 meters (50 feet) through the late 1940s. In 1949, the importation of Colorado River water to the southern Coachella Valley began, resulting in a reduction in ground-water pumping and a recovery of water levels during the 1950s through the 1970s. Since the late 1970s, demand for water in the valley has exceeded deliveries of imported surface water, resulting in increased pumping and associated ground-water-level declines and, consequently, an increase in the potential for land subsidence caused by aquifer-system compaction. Global Positioning System (GPS) surveying and interferometric synthetic aperture radar (InSAR) methods were used to determine the location, extent, and magnitude of the vertical land-surface changes in the southern Coachella Valley. GPS measurements made at 13 geodetic monuments in 1996 and in 2005 in the southern Coachella Valley indicate that the elevation of the land surface had a net decline of 124 to 9 mm ±54 mm (0.41 to 0.03 ft ±0.18 ft) during the 9-year period. Changes at 9 of the 13 monuments exceeded the maximum expected uncertainty of ±54 mm (±0.18 ft) at the 95-percent confidence level, indicating that subsidence occurred at these monuments between June 1996 and August 2005. GPS measurements made at 20 geodetic monuments in 2000 and in 2005 indicate that the elevation of the land surface changed –192 to +51 mm ±36 mm (–0.63 to +0.17 ft ±0.12 ft) during the 5-year period. Changes at 6 of the 20 monuments exceeded the maximum expected uncertainty of ±36 mm (±0.12 ft) at the 95-percent confidence level—subsidence occurred at five monuments and uplift occurred at one monument between August 2000 and August 2005. GPS measurements at two of the five subsiding monuments for which subsidence rates could be compared indicate that subsidence rates decreased during this period compared with subsidence rates before 2000. InSAR measurements made between May 7, 2003, and September 25, 2005, indicate that land subsidence, ranging from about 75 to 180 millimeters (0.25 to 0.59 foot), occurred in three areas of the Coachella Valley: near Palm Desert, Indian Wells, and La Quinta; the equivalent subsidence rates range from about 3 to more than 6 mm/month (0.01 to 0.02 ft/month). The subsiding areas near Palm Desert, Indian Wells, and La Quinta were previously identified using InSAR measurements for 1996–2000, which indicated that about 35 to 150 mm (0.11 to 0.49 ft) of subsidence occurred during the four-year period; the equivalent subsidence rates range from about 1 to 3 mm/month (0.003 to 0.01 ft/month). Comparison of the InSAR results indicates that subsidence rates have increased 2 to 4 times since 2000 in these three areas. Water-level measurements made at wells near the subsiding monuments and in the three subsiding areas generally indicated that the water levels fluctuated seasonally and declined annually between 1996 and 2005; some water levels in 2005 were at the lowest levels in their recorded histories. The coincident areas of subsidence and declining water levels suggest that aquifer-system compaction may be causing subsidence. If the stresses imposed by the historically lowest water levels exceeded the preconsolidation stress, the aquifer-system compaction and associated land subsidence may be permanent. Although the localized character of the subsidence signals is typical of the type of subsidence characteristically caused by localized ground-water pumping, the subsidence may also be related to tectonic activity in the valley.

Detection and Measurement of Land Subsidence Using Interferometric Synthetic Aperture Radar and Global Positioning System, San Bernardino County, Mojave Desert, California

U.S. Geological Survey (USGS) | July 1st, 2003

Detection and Measurement of Land-Surface Deformation, Pajaro Valley, Santa Cruz and Monterey Counties, California, 2015–18

U.S. Geological Survey (USGS) | October 22nd, 2021

Land-surface deformation (subsidence) caused by groundwater withdrawal is identified as an undesirable result in the Pajaro Valley Water Management Agency’s Basin Manag

Land-surface deformation (subsidence) caused by groundwater withdrawal is identified as an undesirable result in the Pajaro Valley Water Management Agency’s Basin Management Plan and California’s Sustainable Groundwater Management Act. In Pajaro Valley, groundwater provides nearly 90 percent of the total water supply. To aid the development of sustainable groundwater management criteria, the U.S. Geological Survey, in cooperation with the Pajaro Valley Water Management Agency, performed an analysis of land-surface deformation (subsidence and uplift) in Pajaro Valley for 2015–18, using Interferometric Synthetic Aperture Radar and continuous Global Positioning System methods. Land-surface deformation results were then compared with subsurface geology and groundwater altitudes to better understand the hydromechanical response of the coastal aquifer system. The results indicate the land surface is generally stable with only small magnitudes (less than 1 inch) of seasonal land-surface deformation (subsidence in the summer and uplift in the winter) during 2015–18. During this time, the largest magnitude of land-surface deformation was less than 2 inches of subsidence and was localized in one area just north of the city limits of Watsonville, California. Groundwater altitudes during 2015–18 demonstrated seasonal variability and annual to multi-annual increases after reaching historical lows by the mid-1990s. The small magnitudes of land-surface deformation coupled with groundwater-altitude increases in most areas indicate that the subsidence likely is largely elastic and recoverable. The Corralitos-Pajaro Valley groundwater basin contains fine-grained (clay) sediments that have the potential for permanent aquifer-system compaction and resultant land subsidence. However, groundwater altitudes throughout the Pajaro Valley have increased above historical lows, and observed increases in groundwater altitudes coincided with changes in groundwater management activities. Observed relations between groundwater management activities and groundwater altitudes indicate that management of groundwater supplies could minimize the potential for permanent land-surface deformation in Pajaro Valley.