Abstract
Abstract. 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 compaction 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 everywhere 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.
Highlights
Introduction and BackgroundGroundwater has been a major source of agricultural, municipal and domestic water supply in the Coachella Valley, California, USA, since the early 1920s (Fig. 1)
The stabilization and recovery of groundwater levels, and the reduced rates or cessation of subsidence, correspond to the timing of various conservation, managed aquifer-recharge (MAR), and groundwater substitution projects implemented by the Coachella Valley Water District (CVWD) to increase recharge or reduce reliance on groundwater (Fig. 1c)
Starting in about 2010, the combination of several projects implemented by the CVWD to increase recharge or reduce reliance on groundwater coincided with wide-spread stabilization and recovery of groundwater levels and a substantial slowing or cessation of subsidence in some of the historically most overdrafted areas
Summary
Groundwater has been a major source of agricultural, municipal and domestic water supply in the Coachella Valley, California, USA, since the early 1920s (Fig. 1). Declining water levels can contribute to, or induce, land subsidence in alluvial aquifer systems with compressible fine-grained deposits such as that of the Coachella Valley. Aperture Radar (InSAR) analyses were used to determine that as much as 0.6 m of subsidence occurred during 1995–2010 along the southwestern margins of Coachella Valley in the urban areas of Palm Desert, Indian Wells and La Quinta (Sneed et al, 2014; Fig. 1b). In 2014, the California legislature passed the Sustainable Groundwater Management Act (SGMA), which stipulates sustainable management of groundwater resources by avoiding certain “undesirable results,” including groundwater-level declines and land subsidence.
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