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 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.

Development and Application of a 1D Compaction Model to Understand 65 Years of Subsidence in the San Joaquin Valley

American Geophysical Union (AGU) | June 2nd, 2022

High rates of land subsidence, caused by groundwater overdraft, are resulting in millions of dollars of infrastructure damage in California's San Joaquin Valley (SJV). In

High rates of land subsidence, caused by groundwater overdraft, are resulting in millions of dollars of infrastructure damage in California's San Joaquin Valley (SJV). In recent years, the use of interferometric synthetic aperture radar (InSAR) has enabled us to substantially improve our understanding of this subsidence. However, only very occasionally have the InSAR data been integrated with a physical model of subsurface compaction. Here, we have used InSAR and other data to parameterize and calibrate a 1D compaction model. We applied our model to a study area in the SJV where we had access to the necessary information on hydraulic head to develop model inputs. Our model simulated subsidence in the three aquifer system layers over the period 1952–2017, and is the first 1D compaction model in the SJV to simulate multiple aquifer system layers from the 1950s to 2017. The results from our model suggest that previous studies have significantly underestimated the time constants governing the slow, residual compaction of subsurface clays. We suggest that residual compaction of clays is a process that continues for decades-to-centuries, indicating that to significantly reduce subsidence requires some recovery of head, not just a stabilization. We also show how compaction in the lower, confined aquifer has accounted for over 90% of subsidence in the past 20 years. Although our study area is small, our findings are likely representative of the subsiding regions of the SJV, and our methodology can be applied to unconsolidated aquifer systems exhibiting subsidence worldwide.

Domestic well vulnerability to drought duration and unsustainable groundwater management in California's Central Valley

Environmental Research Letters (IOP) | March 18th, 2020

Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and th

Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and the possibility of longer drought duration under climate change threatens domestic well reliability, yet we lack tools to assess the impact of such events. Here, we leverage 943,469 well completion reports and 20 years of groundwater elevation data to develop a spatially-explicit domestic well failure model covering California’s Central Valley. Our model successfully reproduces the spatial distribution of observed domestic well failures during the severe 2012–2016 drought (n=2027). Next, the impact of longer drought duration (5–8years) on domestic well failure is evaluated, indicating that if the 2012–2016 drought would have continued into a 6 to 8 year long drought, a total of 4037–5460 to 6538–8056 wells would fail. The same drought duration scenarios with an intervening wet winter in 2017 lead to an average of 498 and 738 fewer well failures. Additionally, we map vulnerable wells at high failure risk and find that they align with clusters of predicted well failures. Lastly, we evaluate how the timing and implementation of different projected groundwater management regimes impact groundwater levels and thus domestic well failure. When historic overdraft persists until 2040, domestic well failures range from 5966 to 10 466 (depending on the historic period considered). When sustainability is achieved progressively between 2020 and 2040, well failures range from 3677 to 6943, and from 1516 to 2513 when groundwater is not allowed to decline after 2020.

Drawdown ‘‘Triggers’’: A Misguided Strategy for Protecting Groundwater-Fed Streams and Springs

National Groundwater Association (NGWA) | October 31st, 2016

There is increasing recognition of the importanceof groundwater to the survival and function of terrestrial ecosystems (e.g., Ribeiro et al. 2013), which has grown from

There is increasing recognition of the importanceof groundwater to the survival and function of terrestrial ecosystems (e.g., Ribeiro et al. 2013), which has grown from understanding of the intimate connections between groundwater and surface water (Winter et al.1998). In this context, management strategies that can protect groundwater-dependent ecosystems (GDEs) such as springs and groundwater-fed streams are of critical importance. One strategy being adopted in some casesis the use of “drawdown triggers.” This involves specifying an amount of acceptable drawdown relative to baseline at a particular monitoring point, which if exceeded, triggers a management response. This technical commentary examines this strategy, highlighting potential pit-falls. There are important aspects of the response of groundwater and connected springs and streams which may be overlooked if drawdown triggers are adopted as the primary strategy for GDE protection. A case study of a recently approved mining project is discussed and some additional and/or alternative approaches proposed.

Drift of Earth's Pole Confirms Groundwater Depletion as a Significant Contributor to Global Sea Level Rise 1993–2010

American Geophysical Union (AGU) | June 15th, 2023

Drought, water management, and agricultural livelihoods: Understanding human-ecological system management and livelihood strategies of farmer’s in rural California

Elsevier | July 11th, 2024