Apportioning deformation among depth intervals in an aquifer system using InSAR and head data

Ryan G Smith,Rosemary Knight,Hossein Hashemi,Jingyi Chen

doi:10.1007/s10040-021-02386-0

Abstract

Land surface subsidence due to excessive groundwater pumping is an increasing concern in California, USA. Interferometric Synthetic Aperture Radar (InSAR) is a remote sensing technique for measuring centimeter-to-millimeter surface deformation at 10–100 m spatial resolution. Here, a data-driven approach that attributes deformation to individual depth intervals within an aquifer system by integrating head data acquired from each of three screened intervals in a monitoring well with InSAR surface deformation measurements was developed. The study area was the Colusa Basin in northern Central Valley. To reconstruct the surface deformation history over the study area, 13 ALOS-PALSAR scenes acquired between 2006 and 2010 were processed. Up to ~3-cm year−1 long-term subsidence and up to ~6 cm seasonal subsidence were observed using the InSAR technique. The technique developed in this paper integrates the InSAR-observed seasonal deformation rate and the co-located head measurements in multiple depth intervals to estimate the elastic skeletal storage coefficient, the time delay between the head change and the observed deformation, and subsequently the deformation of each depth interval. This technique can be implemented when hydraulic head measurements within each depth interval are not correlated with each other. Using this approach, the depth interval that contributed the most to the total subsidence, as well as storage parameters for all intervals, are estimated. The technique can be used for identification of the depth interval within the aquifer system responsible for deformation.

Highlights

In the Central Valley of California, USA, groundwater pumping for irrigation has increased dramatically due to the recurrent droughts in the past decade
A maximum long-term subsidence rate of about 3 cm year−1 occurred in the portion of the Colusa Basin between Orland and Willows cities, where the head dropped ~12 m between 2004 and 2015 (DWR, CA, Northern Region office, 2015)
The portion of the aquifer adjacent to the river is directly recharged from the riverbed and bank, reducing the subsidence in response to groundwater pumping

Summary

Introduction

In the Central Valley of California, USA, groundwater pumping for irrigation has increased dramatically due to the recurrent droughts in the past decade. Much of the Central Valley’s aquifer system is composed of fine-grained materials that are highly prone to compaction due to water extraction (Leake and Prudic 1991; Williamson et al 1989). Excessive pumping in some areas has led to aquifer compaction and associated subsidence that can be observed at the ground surface (Farr and Liu 2014; Faunt et al 2009, 2016; Poland et al 1975). In addition to the potential impact on infrastructure, aquifer compaction due to over-pumping can be permanent if the groundwater level declines beyond the maximum historical stress (Riley 1969). In one region of the San Joaquin Valley, the southern part of the Central Valley, there has been 25 cm year−1 of permanent compaction over the 2007–2010 and 20122015 drought periods, with significant delayed compaction for several years following the droughts (Chaussard and Farr 2019; Smith and Knight 2019; Smith et al 2017).

Methods

Results

Conclusion