Quantifying Changes in Groundwater Storage and Response to Hydroclimatic Extremes in a Coastal Aquifer Using Remote Sensing and Ground-Based Measurements: The Texas Gulf Coast Aquifer

Bimal Gyawali,Dorina Murgulet,Mohamed Ahmed

doi:10.3390/rs14030612

Bimal Gyawali, Dorina Murgulet + Show 1 more

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https://doi.org/10.3390/rs14030612

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Journal: Remote sensing	Publication Date: Jan 27, 2022
Citations: 5	License type: CC BY 4.0

Affiliation: Texas A&M University – Corpus Christi

Abstract

With the increasing vulnerability of groundwater resources, especially in coastal regions, there is a growing need to monitor changes in groundwater storage (GWS). Estimations of GWS have been conducted extensively at regional to global scales using GRACE and GRACE-FO observations. The major goal of this study was to evaluate the applicability of uninterrupted monthly GRACE-derived terrestrial water storage (TWSGRACE) records in facilitating detection of long- and short-term hydroclimatic events affecting the GWS in a coastal area. The TWSGRACE data gap was filled with reconstructed values from multi-linear regression (MLR) and artificial neural network (ANN) models and used to estimate changes in GWS in the Texas coastal region (Gulf Coast and Carrizo–Wilcox Aquifers) between 2002 and 2019. The reconstructed TWSGRACE, along with soil moisture storage (SMS) from land surface models (LSMs), and surface water storage (SWS) were used to estimate the GRACE-derived GWS (GWSGRACE), validated against the GWS estimated from groundwater level observations (GWSwell) and extreme hydroclimatic event records. The results of this study show: (1) Good agreement between the predicted TWSGRACE data gaps from the MLR and ANN models with high accuracy of predictions; (2) good agreement between the GWSGRACE and GWSwell records (CC = 0.56, p-value < 0.01) for the 2011–2019 period for which continuous GWLwell data exists, thus validating the approach and increasing confidence in using the reconstructed TWSGRACE data to monitor coastal GWS; (3) a significant decline in the coastal GWSGRACE, at a rate of 0.35 ± 0.078 km3·yr−1 (p-value < 0.01), for the 2002–2019 period; and (4) the reliable applicability of GWSGRACE records in detecting multi-year drought and wet periods with good accuracy: Two drought periods were identified between 2005–2006 and 2010–2015, with significant respective depletion rates of −8.9 ± 0.95 km3·yr−1 and −2.67 ± 0.44 km3·yr−1 and one wet period between 2007 and 2010 with a significant increasing rate of 2.6 ± 0.63 km3·yr−1. Thus, this study provides a reliable approach to examine the long- and short-term trends in GWS in response to changing climate conditions with significant implications for water management practices and improved decision-making capabilities.

Highlights

Groundwater is the main source of freshwater for almost half of the world’s population; it provides a major resource for irrigation and plays a key role in ecosystem health [1,2].Yet, groundwater resources are under extreme threat due to rapid depletion [3,4,5,6], a serious global issue affecting groundwater resource sustainability and ecosystem health
While we used the averaged TWSGRACE solution generated from three spherical harmonic (SH) and two mascon solutions, we examined the agreements of the individual solutions (Figure 4a)
The short-term changes in TWSGRACE and GWSGRACE trends observed in this study are attributed mainly to climatic variabilities, which when compounded by anthropogenic stressors result in different response times in the storage compartments

Summary

Introduction

Groundwater is the main source of freshwater for almost half of the world’s population; it provides a major resource for irrigation and plays a key role in ecosystem health [1,2].Yet, groundwater resources are under extreme threat due to rapid depletion [3,4,5,6], a serious global issue affecting groundwater resource sustainability and ecosystem health. Groundwater is the main source of freshwater for almost half of the world’s population; it provides a major resource for irrigation and plays a key role in ecosystem health [1,2]. Global groundwater storage (GWS) decreased by 4500 km (~42 km3 ·yr−1 ) between 1900 and 2008, Remote Sens. The depletion rate more than tripled (~145 km3 ·yr−1 ) between 2000 and 2008 [7]. In the United States (U.S.) GWS decreased by 1000 km (~9.3 km3 ·yr−1 ) and the rate doubled after 2000 (~24 km3 ·yr−1 ) [8]. Groundwater is often the only source of freshwater in coastal areas. This source, is vulnerable to climate and anthropogenic variabilities. Coastal regions are among the most densely populated areas that place an increasing demand on coastal aquifers [9,10,11]

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