Characterization of Groundwater Recharge and Flow in California's San Joaquin Valley From InSAR-Observed Surface Deformation

American Geophysical Union (AGU) | March 4th, 2021

Surface deformation in California's Central Valley (CV) has long been linked to changes in groundwater storage. Recent advances in remote sensing have enabled the mappin

Surface deformation in California's Central Valley (CV) has long been linked to changes in groundwater storage. Recent advances in remote sensing have enabled the mapping of CV deformation and associated changes in groundwater resources at increasingly higher spatiotemporal resolution. Here, we use interferometric synthetic aperture radar (InSAR) from the Sentinel-1 missions, augmented by continuous Global Positioning System (cGPS) positioning, to characterize the surface deformation of the San Joaquin Valley (SJV, southern two-thirds of the CV) for consecutive dry (2016) and wet (2017) water years. We separate trends and seasonal oscillations in deformation time series and interpret them in the context of surface and groundwater hydrology. We find that subsidence rates in 2016 (mean −42.0 mm/yr; peak −345 mm/yr) are twice that in 2017 (mean −20.4 mm/yr; peak −177 mm/yr), consistent with increased groundwater pumping in 2016 to offset the loss of surface-water deliveries. Locations of greatest subsidence migrated outwards from the valley axis in the wetter 2017 water year, possibly reflecting a surplus of surface-water supplies in the lowest portions of the SJV. Patterns in the amplitude of seasonal deformation and the timing of peak seasonal uplift reveal entry points and potential pathways for groundwater recharge into the SJV and subsequent groundwater flow within the aquifer. This study provides novel insight into the SJV aquifer system that can be used to constrain groundwater flow and subsidence models, which has relevance to groundwater management in the context of California's 2014 Sustainable Groundwater Management Act (SGMA).

Comment on “Short-lived pause in Central California subsidence after heavy winter precipitation of 2017” by K. D. Murray and R. B. Lohman

American Association for the Advancement of Science (AAAS) | June 12th, 2019

In a study by Murray and Lohman (M&L), the authors suggest that remote sensing data are useful for monitoring land subsidence due to aquifer system compacti

In a study by Murray and Lohman (M&L), the authors suggest that remote sensing data are useful for monitoring land subsidence due to aquifer system compaction. We agree. To infer aquifer dynamics, we provide a more detailed and joint analysis of deformation and groundwater data. Investigating well data in the Tulare Basin, we find that groundwater levels stabilized before 2015 and show that M&L’s observed continued subsidence through July 2016 is likely caused by the delayed compaction of the aquitard. Our analysis suggests the observed 2017 transient uplift is not due to recharge of the aquifer system after heavy winter rainfall because it requires an unrealistic vertical hydraulic gradient nearly five orders of magnitude larger than that typical of Tulare Basin. We find that, regardless of the amount of rainfall, transient annual uplifts of ~3 cm occur in May to June. Using an elastic skeletal storage coefficient of 5 × 10−3, we link this ground uplift to annual groundwater level changes.

Delta Islands and Levees Sacramento – San Joaquin River Delta, California Interim Integrated Feasibility Report/ Environmental Impact Statement

U.S. Army Corps of Engineers (USACE) | November 15th, 2018

USACE initiated the Delta Study in 2006 at the request of the DWR, the non-Federal sponsor for the study. USACE is the lead agency for the Feasibility Study and is also t

USACE initiated the Delta Study in 2006 at the request of the DWR, the non-Federal sponsor for the study. USACE is the lead agency for the Feasibility Study and is also the lead under the National Environmental Policy Act (NEPA). This report: (1) identifies flood risk management and ecosystem restoration problems and opportunities in the Delta; (2) develops and evaluates measures to solve identified problems; (3) formulates and compares alternatives for ecosystem restoration; and (4) identifies a Recommended Plan (RP) for implementation. A draft of this FR/EIS was concurrently released for public review, internal policy review, Agency Technical Review (ATR), and Independent External Peer Review (IEPR). The present report has been updated based on comments received during these reviews and finalized to present the RP for eventual authorization. The RP is the most reasonably efficient contribution to the Delta, restoring 340 acres of intertidal marsh habitat in the Delta at a cost of $25M. The RP provides a unique opportunity to restore intertidal marsh, habitat which is now greatly reduced in this ecosystem of national significance. The RP links the proposed ecosystem restoration actions to historic and ongoing USACE navigation projects, providing a cost effective mechanism to implement otherwise costly subsidence reversal goals. This action would restore habitat for multiple Federally listed species, notably salmonids and Delta smelt. The restored habitat would also benefit millions of migratory fowl on the Pacific Flyway as they travel through the Delta.

Delta Levees – Types, Uses, and Policy Options

Delta Vision Blue Ribbon Task Force (Delta Vision) | August 7th, 2008

This document was developed to support Delta Vision discussions on the role of levees in the Delta’s future. It is to clarify the different types (or design standards)

This document was developed to support Delta Vision discussions on the role of levees in the Delta’s future. It is to clarify the different types (or design standards) of levees that now exist for the Delta and what improvements could be considered. It is especially oriented toward an improved understanding of what types of levees are suitable for protecting various land uses or for other applications. Based on understanding the levee types, policy options are identified for a) selecting levee improvements to be included in the vision of the Delta’s future and b) implementing the improvements selected.

Delta Subsidence in California: The sinking heart of the state

U.S. Geological Survey (USGS) | April 8th, 2000

The Sacramento-San Joaquin River Delta of California once was a great tidal freshwater marsh blanketed by peat and peaty alluvium. Beginning in the late 1800s, levees wer

The Sacramento-San Joaquin River Delta of California once was a great tidal freshwater marsh blanketed by peat and peaty alluvium. Beginning in the late 1800s, levees were built along the stream channels, and the land thus protected from flooding was drained, cleared, and planted. Although the Delta is now an exceptionally rich agricultural area (over a $500 million crop value in 1993), its unique value is as a source of freshwater for the rest of the State. It is the heart of a massive north-to-south water delivery system. Much of this water is pumped southward for use in the San Joaquin Valley and elsewhere in central and southern California. The leveed tracts and islands help to protect water-export facilities in the southern Delta from saltwater intrusion by displacing water and maintaining favorable freshwater gradients. However, ongoing subsidence behind the levees reduces levee stability and, thus, threatens to degrade water quality in the massive north-to-south water-transfer system.

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 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.

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

U.S. Geological Survey (USGS) | April 15th, 1998

Interferometric synthetic aperture radar (InSAR) has great potential to detect and quantify land subsidence caused by aquifer system compaction. InSAR maps with h

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.