Mitigating land subsidence in the Coachella Valley, California, USA: An emerging success story

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

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

Groundwater has been a major source of agricultural, municipal, and domestic water supply since the early 1920s in the Coachella Valley, California, USA. Land subsidence, resulting from aquifer-system com- paction and groundwater-level declines, has been a concern of the Coachella Valley Water District (CVWD) since the mid-1990s. As a result, the CVWD has implemented several projects to address groundwater overdraft that fall under three categories – groundwater substitution, conservation, and managed aquifer-recharge (MAR). The implementation of three projects in particular – replacing groundwater extraction with surface water from the Colorado River and recycled water (Mid-Valley Pipeline project), reducing water usage by tiered-rate costs, and increasing groundwater recharge at the Thomas E. Levy Groundwater Replenishment Facility – are potentially linked to markedly improved groundwater levels and subsidence conditions, including in some of the historically most overdrafted areas in the southern Coachella Valley. Groundwater-level and subsidence monitoring have tracked the effect these projects have had on the aquifer system. Prior to about 2010, water levels persistently declined, and some had reached historically low levels by 2010. Since about 2010, however, groundwater levels have stabilized or partially recovered, and subsidence has stopped or slowed substantially almost every- where it previously had been observed; uplift was observed in some areas. Furthermore, results of Interferometric Synthetic Aperture Radar analyses for 1995–2017 indicate that as much as about 0.6 m of subsidence occurred; nearly all of which occurred prior to 2010. Continued monitoring of water levels and subsidence is necessary to inform the CVWD about future mitigation measures. The water management strategies implemented by the CVWD can inform managers of other overdrafted and subsidence-prone basins as they seek solutions to reduce overdraft and subsidence.

Modeling Land Subsidence Using InSAR and Airborne Electromagnetic Data

American Geophysical Union (AGU) | March 13th, 2019

Land subsidence as a result of groundwater overpumping in the San Joaquin Valley, California, is associated with the loss of groundwater storage and aquifer contaminatio

Land subsidence as a result of groundwater overpumping in the San Joaquin Valley, California, is associated with the loss of groundwater storage and aquifer contamination. Although the physical processes governing land subsidence are well understood, building predictive models of subsidence is challenging because so much subsurface information is required to do so accurately. For the first time, we integrate airborne electromagnetic data, representing the subsurface, with subsidence data, mapped by interferometric synthetic aperture radar (InSAR), to model deformation. By combining both data sets, we are able to solve for hydrologic and geophysical properties of the subsurface to effectively model the complex spatiotemporal process of deformation. The resulting model reveals that roughly 3 m of subsidence has occurred at one location of our study area from 1990 to 2018. This model also allows us to predict subsidence more accurately under future hydrologic scenarios, which is needed to develop plans for sustainable groundwater use.

Modeling the dynamic penetration depth of post-1950s water in unconfined aquifers using environmental tracers: Central Valley, California

Journal of Hydrology (Elsevier) | December 5th, 2022

The penetration depth of post-1950s recharge (D-1950) in aquifers is a marker that is frequently used to identify groundwater that is susceptible to anthropogenic contami

The penetration depth of post-1950s recharge (D-1950) in aquifers is a marker that is frequently used to identify groundwater that is susceptible to anthropogenic contamination. Here, we compute D-1950 values at wells, interpolate them in space, and project them across time to map the moving front of modern recharge in four dimensions in the Central Valley aquifer system, California, USA. Tracers of groundwater age (tritium, carbon-14, noble gases, sulfur hexafluoride, and chlorofluorocarbons) were collected at 650 wells spatially distributed throughout the Central Valley and were fit to a lumped-parameter model that assumes a logarithmic age-depth profile in the aquifer. For samples where tritium was present (>0.3 tritium units), the model was used to predict D-1950 at wells screened above or across the modern-premodern interface (n = 484). Wells with samples where tritium was absent (≤0.3 tritium units) were used to define the depth beyond which groundwater is completely premodern (n = 166). Predicted D-1950 values were below the depth of screen bottoms for wells where groundwater is completely modern, and above the depth of screen tops for wells where groundwater is completely premodern. The interpolated surface of D-1950 is dynamic, less prone to extreme values, and produces maps with lower interpolation errors due to a higher spatial density of wells than maps based on the depth of premodern groundwater. Between 2005 and 2025, D-1950 is expected to deepen by 11 and 12 m in the northern and southern parts of the Central Valley, respectively. Areas where D-1950 increases rapidly are likely to see increases in nitrate and other anthropogenic contaminants associated with the downward moving front of modern water.

Modern groundwater reaches deeper depths in heavily pumped aquifer systems

Nature Portfolio (Springer Nature) | September 7th, 2022

Deep groundwater is an important source of drinking water, and can be preferable to shallower groundwaters where they are polluted by surface-borne contaminants. Surface-

Deep groundwater is an important source of drinking water, and can be preferable to shallower groundwaters where they are polluted by surface-borne contaminants. Surface-borne contaminants are disproportionately common in ‘modern’ groundwaters that are made up of precipitation that fell since the ~1950s. Some local-scale studies have suggested that groundwater pumping can draw modern groundwater downward and potentially pollute deep aquifers, but the prevalence of such pumping-induced downwelling at continental scale is not known. Here we analyse thousands of US groundwater tritium measurements to show that modern groundwater tends to reach deeper depths in heavily pumped aquifer systems. These findings imply that groundwater pumping can draw mobile surface-borne pollutants to deeper depths than they would reach in the absence of pumping. We conclude that intensive groundwater pumping can draw recently recharged groundwater deeper into aquifer systems, potentially endangering deep groundwater quality.

New Stone Water District GSA Groundwater Sustainability Plan

New Stone Water District (NSWD) | September 23rd, 2019

North Fork Kings Groundwater Sustainability Agency Groundwater Sustainability Plan (Revised)

North Fork Kings Groundwater Sustainability Agency (NFKGSA) | July 14th, 2022

North Fork Kings Groundwater Sustainability Plan

North Fork Kings Groundwater Sustainability Agency (NFKGSA) | December 18th, 2019

North Kings Groundwater Sustainability Groundwater Sustainability Plan

North Kings Groundwater Sustainability Agency | November 21st, 2019

One‐dimensional simulation of aquifer system compaction near Pixley, California: 1. Constant parameters

American Geophysical Union (AGU) | June 12th, 1975

Aggregate one‐dimensional compaction (consolidation) of a series of aquitards in a compacting aquifer system has been simulated through use of a finite difference repre

Aggregate one‐dimensional compaction (consolidation) of a series of aquitards in a compacting aquifer system has been simulated through use of a finite difference representation of the vertical stress distribution within an idealized aquitard. Among the parameters affecting the simulated compaction are two storage coefficients (compressibility values), one for recoverable and the other for nonrecoverable compression. These two storage coefficients introduce a transient heterogeneity within an aquitard that is generally ignored by hydrologists. A computer program with two sets of constant coefficients calculates the daily deformation due to observed changes in applied stress near Pixley, California. Although water levels fluctuate annually, no long‐term water level decline occurred near Pixley between January 1, 1959, and February 4, 1971. During this period, 3.19 ft (0.972 m) of compaction was observed. The net difference between simulated and observed compaction on February 4, 1971, was 1.3% of the observed value. Maximum deviation occurred in mid‐1964 and equaled 7% of the observed compaction.

Pajaro Valley Water Management Agency Basin Management Plan Update

Pajaro Valley Water Management Agency (PVWMA) | February 14th, 2014