Comparison of Groundwater Storage Changes From GRACE Satellites With Monitoring and Modeling of Major U.S. Aquifers

Abstract

GRACE satellite data are widely used to estimate groundwater storage (GWS) changes in aquifers globally; however, comparisons with GW monitoring and modeling data are limited. Here we compared GWS changes from GRACE over 15 yr (2002-2017) in 14 major U.S. aquifers with groundwater-level (GWL) monitoring data in~23,000 wells and with regional and global hydrologic and land surface models. Results show declining GWS trends from GRACE data in the six southwestern and south-central U.S. aquifers, totaling −90 km 3 over 15 yr, related to long-term (5-15 yr) droughts, and exceeding Lake Mead volume by~2.5×. GWS trends in most remaining aquifers were stable or slightly rising. GRACE-derived GWS changes agree with GWL monitoring data in most aquifers (correlation coefficients, R = 0.52-0.95), showing that GRACE satellites capture groundwater (GW) dynamics. Regional GW models (eight models) generally show similar or greater GWS trends than those from GRACE. Large discrepancies in the Mississippi Embayment aquifer, with modeled GWS decline approximately four times that of GRACE, may reflect uncertainties in model storage parameters, stream capture, pumpage, and/or recharge rates. Global hydrologic models (2003-2014), which include GW pumping, generally overestimate GRACE GWS depletion (total: approximately −172 to −186 km 3) in heavily exploited aquifers in southwestern and south-central U.S. by~2.4× (GRACE: −74 km 3), underscoring needed modeling improvements relative to anthropogenic impacts. Global land surface models tend to track GRACE GWS dynamics better than global hydrologic models. Intercomparing remote sensing, monitoring, and modeling data underscores the importance of considering all data sources to constrain GWS uncertainties. Plain Language Summary The major U.S. aquifers provide an ideal system to assess GRACE (Gravity Recovery and Climate Experiment) satellite data. We compared GRACE groundwater storage anomalies (GWSAs) with groundwater level anomalies (GWLAs) from~23,000 wells and with groundwater storage (GWS) from regional and global models in 14 major U.S. aquifers. Results show large GWS declines from GRACE in southwestern (Central Valley and Arizona Alluvial Basins) and south-central (Central and Southern High Plains and Texas) aquifers from multiyear droughts (5-15 yr). In contrast, GWS trends in aquifers throughout the rest of the U.S. showed mostly stable or rising values. Time series of GRACE GWSAs compared favorably with GWLAs from most aquifers, suggesting that GRACE data track groundwater (GW) dynamics. Regional GW models show similar or greater declines in GWS compared with GRACE data, with the largest discrepancy of a factor of four times greater modeled depletion in the ©2020. American Geophysical Union. All Rights Reserved.

Post‐Drought Groundwater Storage Recovery in California's Central Valley

“…We compared GWS estimates for three different storage coefficients and settled on an effective storage coefficient (Se = 0.06). We determined Se based on comparison of GWS changes between the GRACE and well-based estimates, where we followed the method used by (Rateb et al, 2020). Using Se was characterized as a pragmatic solution for GWS estimation by (Rateb et al, 2020) due to inadequate information on well depths, storage coefficients, limited groundwater level measurements, and limited knowledge of lower aquifer thickness (see details provided in Section 3.2.1 and Text S5 and Figures S16-S17).…”

“…We determined Se based on comparison of GWS changes between the GRACE and well-based estimates, where we followed the method used by (Rateb et al, 2020). Using Se was characterized as a pragmatic solution for GWS estimation by (Rateb et al, 2020) due to inadequate information on well depths, storage coefficients, limited groundwater level measurements, and limited knowledge of lower aquifer thickness (see details provided in Section 3.2.1 and Text S5 and Figures S16-S17). Moreover, we acknowledge that there is a co-dependency between the GRACE and well-based estimates, as well as (to a somewhat lesser extent) among other methods as well.…”

“…We estimated GWS using three storage coefficients (C2VSIM model Sy, CVHM model Sy and effective storage). We determined effective storage coefficients by correlating GWSA from GRACE and well-based estimates similar to the previous study of (Rateb et al, 2020) which estimated GWS in 14 major U.S. aquifers. Rateb et al (2020) study showed the limitations of attempting to distinguish wells in confined and unconfined aquifers due to lack of adequate well depth information necessary to develop composite groundwater level hydrographs.…”

Introduction to Special Section: The Quest for Sustainability of Heavily Stressed Aquifers at Regional to Global Scales

“…Rateb et al. (2020) compare the GRACE water‐storage estimates with those derived from water‐level monitoring data and regional and global models for 14 major aquifers in the US.…”

Optimization of Groundwater Exploitation in an Irrigation Area in the Arid Upper Peacock River, NW China: Implications for Sustainable Agriculture and Ecology

“…Groundwater is the primary water resources for domestic, industrial, and agricultural use in many arid and semi-arid regions [1][2][3]. In recent years, groundwater shortage has drawn much concern in these regions under the stress of climate change and anthropogenic activities [4][5][6][7][8][9], such as the large aquifers in Eastern and Northern Africa, the California's Central Valley, and Southern Plains in North America, south-eastern Spain, North China Plain, and Middle East [10][11][12][13][14][15][16][17]. Strategies such as introducing substitute water, artificial recharge, water saving and reuse, and groundwater management are applied in order to ensure the sustainable use of groundwater [18][19][20][21][22].…”