Groundwater Storage Depletion Research Articles

CO2 Emissions Associated with Groundwater Storage Depletion in South Korea: Estimation and Vulnerability Assessment Using Satellite Data and Data-Driven Models

Groundwater is crucial in mediating the interactions between the carbon and water cycles. Recently, groundwater storage depletion has been identified as a significant source of carbon dioxide (CO2) emissions. Here, we developed two data-driven models—XGBoost and convolutional neural network–long short-term memory (CNN-LSTM)—based on multi-satellite and reanalysis data to monitor CO2 emissions resulting from groundwater storage depletion in South Korea. The data-driven models developed in this study provided reasonably accurate predictions compared with in situ groundwater storage anomaly (GWSA) observations, identifying relatively high groundwater storage depletion levels in several regions over the past decade. For each administrative region exhibiting a decreasing groundwater storage trend, the corresponding CO2 emissions were quantified based on the predicted GWSA and respective bicarbonate concentrations. For 2008–2019, XGBoost and CNN-LSTM estimated CO2 emissions to be 0.216 and 0.202 MMTCO2/year, respectively. Furthermore, groundwater storage depletion vulnerability was assessed using the entropy weight method and technique for order of preference by similarity to ideal solution (TOPSIS) to identify hotspots with a heightened potential risk of CO2 emissions. Western South Korean regions were particularly classified as high or very high regions and susceptible to groundwater storage depletion-associated CO2 emissions. This study provides a foundation for developing countermeasures to mitigate accelerating groundwater storage depletion and the consequent rise in CO2 emissions.

Quantifying groundwater depletion in Arabian Peninsula transboundary aquifer systems: Understanding natural and anthropogenic drivers

Groundwater is the primary source of freshwater for domestic, agricultural, and industrial usage in the Arabian Peninsula countries. It is increasingly becoming a limited resource due to human activities leading to excessive depletion and contamination. Thus, sustainable management of groundwater resources in this region is critical. The groundwater in the Arabian Peninsula countries is primarily found in transboundary systems such as the Wajid, Umm Er Radhuma, and Wasia Aquifers shared between Saudi Arabia, Iraq, Syria, Yemen, and Oman. These systems have no groundwater-sharing agreements, which leads to a lack of data sharing, unsustainable and uncoordinated development, rapid water depletion, water quality deterioration, and land subsidence. This study examines the Wajid, Umm Er Radhuma, and Wasia aquifer systems from April 2002 to May 2021 by analyzing monthly gravity field solutions from GRACE and GRACE-FO satellite data, other remote sensing observations, information from the Global Land Data Assimilation System (GLDAS), as well as field data to determine how regional water resources are changing over time and to identify the factors that influence these resources. The sharp decline in Total Water Storage Anomalies (TWSA) and the Groundwater Storage Anomalies (GWSA) across all three systems is caused by a combination of climatic and human factors. The observed decline in Total Water Storage can be partly attributed to a decrease in regional rainfall, whereas the depletion of Groundwater Storage has a strong correlation with the rise in groundwater extraction for irrigation purposes in the 2010s. The recent rise is groundwater depletion in specific areas of central Saudi Arabia may be attributed to agricultural irrigation and rapid urban development. The results are insightful for monitoring water storage in management plans and decision-making processes to preserve and efficiently use groundwater resources.

Downscaled‐GRACE Data Reveal Anthropogenic and Climate‐Induced Water Storage Decline Across the Indus Basin

AbstractGRACE (Gravity Recovery and Climate Experiment) has been widely used to evaluate terrestrial water storage (TWS) and groundwater storage (GWS). However, the coarse‐resolution of GRACE data has limited the ability to identify local vulnerabilities in water storage changes associated with climatic and anthropogenic stressors. This study employs high‐resolution (1 km2) GRACE data generated through machine learning (ML) based statistical downscaling to illuminate TWS and GWS dynamics across twenty sub‐regions in the Indus Basin. Monthly TWS and GWS anomalies obtained from a geographically weighted random forest (RFgw) model maintained good consistency with original GRACE data at the 25 km2 grid scale. The downscaled data at 1 km2 resolution illustrate the spatial heterogeneity of TWS and GWS depletion within each sub‐region. Comparison with in‐situ GWS from 2,200 monitoring wells shows that downscaling of GRACE data significantly improves agreement with in‐situ data, evidenced by higher Kling‐Gupta Efficiency (0.50–0.85) and correlation coefficients (0.60–0.95). Hotspots with the highest TWS and GWS decline rate between 2002 and 2023 were Dehli Doab (−442, −585 mm/year), BIST Doab (−367, −556 mm/year), Rajasthan (−242, −381 mm/year), and BARI (−188, −333 mm/year). Based on a general additive model, 47%–83% of the TWS decline was associated with anthropogenic stressors mainly due to increasing trends of crop sown area, water consumption, and human settlements. The decline rate of TWS and GWS anomalies was lower (i.e., −25 to −75 mm/year) in upstream sub‐regions (e.g., Yogo, Gilgit, Khurmong, Kabul) where climatic factors (downward shortwave radiations, air temperature, and sea surface temperature) explained 72%–91% of TWS/GWS changes. The relative influences of climatic and anthropogenic stressors varied across sub‐regions, underscoring the complex interplay of natural‐human activities in the basin. These findings inform place‐based water resource management in the Indus Basin by advancing the understanding of local vulnerabilities.

Catchment-Wide Groundwater Budget for the Inkomati-Usuthu Water Management Area in South Africa.

In South Africa, approximately 98% of the predicted total surface water resources are already being used up. Consequently, the National Water Resource Strategy considers groundwater to be important for the future planning and management of water resources. In this case, quantifying groundwater budgets is a prerequisite because they provide a means for evaluating the availability and sustainability of a water supply. This study estimated the regional groundwater budgets for the Inkomati-Usuthu Water Management Area (Usuthu, Komati, Sabie-Sand, and Crocodile) using the classical hydrological continuity equation. The equation was used to describe prevailing feedback loops between groundwater draft, recharge, baseflow, and storage change. The results were coarser scale estimates which, beforehand, were derived from the 2006 study. In the years to follow, groundwater reliance intensified and there was also the historic 2015/2016 drought. This inevitably led to an increased draft while the rest of the components of the groundwater budgets experienced decreases. Both Crocodile and Sabie-Sand experienced groundwater storage depletion which led to reduced baseflow and groundwater availability, while groundwater recharge contrarily increased due to capture. Conversely, the other two catchments experienced relatively lower drafts with correspondingly higher groundwater availability and recharge while storage change was positive. The results highlighted the need for adaptive water management whose effectiveness relies on predictive studies. Consequently, future models should be developed to capture the spatial and temporal dynamism of the natural groundwater budget due to climate change, water demands, and population growth predictions.

Risks in the current groundwater regulation approach in the Beetaloo region, Northern Territory, Australia

ABSTRACT Plans are underway to greatly increase rates of groundwater extraction from the Northern Territory’s Cambrian Limestone Aquifer (CLA), particularly above the Beetaloo sub-basin, to allow expansion of shale gas and agricultural industries. We analyse current groundwater regulations in the NT, and the state of knowledge regarding key aspects of the region’s hydrogeology and values sustained by groundwater. We find that the current rules governing the administration of groundwater licencing in areas without a Water Allocation Plan (WAP) – the Top End and Arid Zone rules – are poorly suited to protect ecological, Indigenous socio-cultural and other water use values. These rules (as currently applied) allow the depletion of substantial groundwater storage in areas that fall within the ‘arid zone’ (as defined in NT policy). Such depletion risks the reduction or loss of groundwater flows to ecosystems and stygofauna habitat and reduced throughflow of groundwater between different regions, within the highly connected CLA system. This may disrupt water flows that sustain local livelihoods and those that are integral to Indigenous peoples’ beliefs and cultural practices. The new WAP that applies over much of the Beetaloo sub-basin (Georgina-Wiso WAP) is also deficient in key areas. It has failed to comply with national water policy, in that no substantive steps have been taken to understand Indigenous cultural and ecological values sustained by groundwater prior to setting an Estimated Sustainable Yield. A more precautionary, inclusive approach to determining groundwater regulations would involve a) setting of conservative water extraction limits combined with trigger levels for ecosystem protection and b) co-management in partnership with Aboriginal peoples, with both consultation and decision-making processes that recognise their inherent rights and interests in water. This will be critical to avoiding long-term environmental and socio-cultural harm from over-extraction of groundwater.

A review of satellite-based monitoring of groundwater storage changes and depletion consequences

Groundwater demand is increasing due to global population growth, climate change and rapid urbanization, however, poor planning and over-exploitation are leading to rapid depletion of groundwater, which in turn causes adverse impacts such as land subsidence, soil salinization and water quality deterioration. Groundwater storage (GWS) monitoring is essential to the sustainable management of regional water resources and the prevention of environmental and social issues associated with depleted groundwater resources. Conventional groundwater observation is primarily conducted through groundwater well-level measurements, which requires a lot of time and effort, and is insufficient to accurately reflect GWS changes regionally and monitor large-scale groundwater level changes. The availability of various satellite data makes it easier to study groundwater information effectively. The aim of this paper is to first review the seriousness of groundwater depletion, every year, 15% to 25% of the total global groundwater extraction is overexploited. Then, based on satellite geodetic technologies such as Gravity Restoration and Climate Experiment (GRACE), GRACE Follow-On, Sentinel-1, and Global Navigation Satellite System (GNSS), the basic principles of GWS monitoring are expounded. The reliability of the monitoring results was analyzed through the literature summary, showing that the results were basically consistent with the trends reflected by the measured groundwater samples, and the statistical significance of quantitative comparisons was higher than 0.65. The impact of the consequences of groundwater depletion also deserves our attention. This paper combined with multi-source satellite and tidal data, etc., the feasible research methods are discussed for a series of adverse consequences caused by groundwater depletion.

Ambiguities in implementing regulations for sustainable groundwater resources development in Vietnam with a case study of Tra Vinh province in Mekong Delta

Study regionThe study region is the coastal Tra Vinh province located in Mekong Delta, Vietnam Study focusThe study aims to clarify the ambiguities in implementing Vietnam's regulation on restrictions of groundwater abstraction in Mekong Delta. Three ambiguities were identified, namely, how should half of the saturated thickness of the unconfined aquifer be computed; is the water level depth of 30 m for the confined aquifer sufficient to prevent seawater intrusion and land subsidence; and why is the interference of water use rights of neighbouring provinces not considered. Numerical groundwater flow, saltwater transport and land subsidence were constructed for Tra Vinh province to assess water level requirements from Vietnam regulation and important constraints for groundwater sustainability. The model results show that although all scenarios satisfy groundwater level requirements from the Vietnam regulation, only the mitigation scenario combined with reducing abstraction and increasing recharge can lead to sustainable development. New hydrological insights for the regionThe current groundwater abstraction in Tra Vinh province has caused groundwater storage depletion and induced seawater intrusion, land subsidence, and captured groundwater inflow from neighbouring provinces. When the business as usual continues, seawater may intrude 4–5 km inland and cumulative land subsidence may reach 1.5 m by 2100. Reduction of current abstraction by 50% supplemented with the increase of recharge by 1.5 times in the dunes can lead to sustainable development.

Twenty-Year Spatiotemporal Variations of TWS over Mainland China Observed by GRACE and GRACE Follow-On Satellites

Terrestrial water storage (TWS) is a pivotal component of the global water cycle, profoundly impacting water resource management, hazard monitoring, and agriculture production. The Gravity Recovery and Climate Experiment (GRACE) and its successor, the GRACE Follow-On (GFO), have furnished comprehensive monthly TWS data since April 2002. However, there are 35 months of missing data over the entire GRACE/GFO observational period. To address this gap, we developed an operational approach utilizing singular spectrum analysis and principal component analysis (SSA-PCA) to fill these missing data over mainland China. The algorithm was demonstrated with good performance in the Southwestern River Basin (SWB, correlation coefficient, CC: 0.71, RMSE: 6.27 cm), Yangtze River Basin (YTB, CC: 0.67, RMSE: 3.52 cm), and Songhua River Basin (SRB, CC: 0.66, RMSE: 7.63 cm). Leveraging two decades of continuous time-variable gravity data, we investigated the spatiotemporal variations in TWS across ten major Chinese basins. According to the results of GRACE/GFO, mainland China experienced an average annual TWS decline of 0.32 ± 0.06 cm, with the groundwater storage (GWS) decreasing by 0.54 ± 0.10 cm/yr. The most significant GWS depletion occurred in the Haihe River Basin (HRB) at −2.07 ± 0.10 cm/yr, significantly substantial (~1 cm/yr) depletions occurred in the Yellow River Basin (YRB), SRB, Huaihe River Basin (HHB), Liao-Luan River Basin (LRB), and Southwest River Basin (SWB), and moderate losses were recorded in the Northwest Basin (NWB, −0.34 ± 0.03 cm/yr) and Southeast River Basin (SEB, −0.24 ± 0.10 cm/yr). Furthermore, we identified that interannual TWS variations in ten basins of China were primarily driven by soil moisture water storage (SMS) anomalies, exhibiting consistently and relatively high correlations (CC > 0.60) and low root-mean-square errors (RMSE < 5 cm). Lastly, through the integration of GRACE/GFO and Global Land Data Assimilation System (GLDAS) data, we unraveled the contrasting water storage patterns between northern and southern China. Southern China experienced drought conditions, while northern China faced flooding during the 2020–2023 La Niña event, with the inverse pattern observed during the 2014–2016 El Niño event. This study fills in the missing data and quantifies water storage variations within mainland China, contributing to a deeper insight into climate change and its consequences on water resource management.

Contributions of Climate Variability and Anthropogenic Activities to Confined Groundwater Storage in Hengshui, North China Plain

Groundwater storage (GWS) in confined aquifer systems is often influenced by climate variability and anthropogenic activities, and it is vital to quantify their contributions for the purpose of groundwater management and surface water allocation plans. In this study, we characterize the spatiotemporal evolution of the GWS in confined aquifer systems across Hengshui, North China Plain, and investigate its relationships with changing climate conditions and human activities through the integration of InSAR-derived surface displacements with hydraulic head observations and precipitation data, during 2004–2010 and 2016–2020. Our results indicate that the GWS in confined aquifer systems decreased markedly by 4.59 ± 0.35 km3 with an accelerating trend during the study period. The GWS variations show a strong correlation with precipitation during irrigation periods (March to July), and hence, the climate and anthropogenic-driven GWS variations can be separated from each other with a linear model. We find that the GWS depletion caused by climate variability and anthropogenic activities were −0.31 ± 0.10 km3 and −4.28 ± 0.40 km3, respectively, during the study period. The mean contribution of anthropogenic activities to the GWS variations was −71.9%, implying that the GWS variations in confined aquifer systems were primarily anthropogenic driven. It is also found that the well observations alone poorly characterize the spatiotemporal evolution of the GWS due to their limited spatial density, and the integrated InSAR/well approach appears to be promising for overcoming this challenge.

Coupled processes of groundwater dynamics and land subsidence in the context of active human intervention, a case in Tianjin, China

To address the crisis of water shortage in the North China Plain, the Chinese government implemented the South-to-North Water Transfer Project (SNWTP). In this context, Tianjin, one of the main beneficiaries of this project, has been relieved from water shortages and begun to implement Groundwater Management Plans (GMP) since 2018, which undoubtedly have a significant effect on the groundwater recovery. Meanwhile, this provides a good case for studying the coupled process of ground settlement and groundwater dynamics, especially the soil deformation pattern driven by groundwater level (GWL) rebound. To analyze these issues in detail, field well data was collected to depict groundwater flow field. Moreover, geodetic data was also collated, including leveling, GPS, and InSAR, so that a vertical deformation field with high spatiotemporal resolution could be generated. The results reveal that the GWL of the third confined aquifer which is the main exploitation layer in Tianjin recovered significantly since 2018 with a rate of 2.1 m/yr. The dynamic deformation patterns indicate that the area of land subsidence cones in Tianjin has reduced significantly, accompanied by a sharply declining subsidence rate (decreased from −32.2 mm/yr to −4.5 mm/yr.). Particularly, a significant poroelastic rebound has occurred in the Wuqing and Beichen districts since 2020. Furthermore, due to the delayed pore pressure dissipation in the aquitard, we find a time delay of 0.3–5.5 years between land subsidence and GWL time series, which is far less than that estimated by hydrogeological parameters, as the latter ignored the recharge and recovery capacity of the aquifer system. Finally, an evolution models in Tianjin was presented to illustrate interactive process among the deformation, pore pressure, and hydraulic head. In general, the SNWDP and the GMP has restored the pore pressure of aquifer, reduced the land subsidence, and alleviated the groundwater storage depletion of Tianjin.

Simulation of groundwater flow and seawater intrusion in response to climate change and human activities on the coastal aquifer of Gaza Strip, Palestine

This study has investigated the potential impact of human activities and climate change on the groundwater budget, water levels, and seawater intrusion in the coastal aquifer of the Gaza Strip (State of Palestine) over the next two decades. The impact of a proposed measure to use alternative freshwater provision from desalinated seawater on the future groundwater quantity and quality was also analyzed. Following extensive analysis of available observed data, a three-dimensional groundwater flow model, coupled with variable-density saltwater flow and transport components, was utilized for the investigations. Compared with the benchmark scenario (SC0), the climate change scenario (SC1) suggests that over the next two decades, an average annual aquifer recharge of 6.3 Mm3 can be expected, while the human activities scenario (SC2) indicates that the groundwater levels will decline at a rate of 0.09 m/year with expected urban area expansion. The combined human activities and climate change scenario (SC3) indicate severe groundwater storage depletion and seawater intrusion over the next two decades. The alternative freshwater provision scenario (SC4) indicates a strongly positive response in groundwater recovery (quantity and quality) over the next decades. The findings of this study emphasize strongly that the human activity impact, rather than climate change, is the driving force of groundwater depletion and that groundwater recovery interventions will be crucial in the future and should be implemented urgently.

Satellite-based estimates of groundwater storage depletion over Egypt

An arid climate accompanied by a freshwater shortage plagued Egypt. It has resorted to groundwater reserves to meet the increasing water demands. Fossil aquifers were lately adopted as the sole water source to provide the irrigation water requirements of the ongoing reclamation activities in barren areas. Yet, the scarcity of measurements regarding the changes in the aquifers’ storage poses a great challenge to such sustainable resource management. In this context, the Gravity Recovery and Climate Experiment (GRACE) mission enables a novel consistent approach to deriving aquifers’ storage changes. In this study, the GRACE monthly solutions during the period 2003–2021 were utilized to estimate alterations in terrestrial water storage (TWS) throughout Egypt. Changes in groundwater storage (GWS) were inferred by subtracting soil water content, derived from the GLDAS-NOAH hydrological model, from the retrieved TWS. The secular trends in TWS and GWS were obtained using the linear least square method, while the non-parametric technique (Mann–Kendall’s tau) was applied to check the trend significance. The derived changes in GWS showed that all aquifers are undergoing a significant loss rate in their storage. The average depletion rate over the Sinai Peninsula was estimated at 0.64 ± 0.03 cm/year, while the depletion rate over the Nile delta aquifer was 0.32 ± 0.03 cm/year. During the investigated period (2003–2021), the extracted groundwater quantity from the Nubian aquifer in the Western Desert is estimated at nearly 7.25 km3. The storage loss from the Moghra aquifer has significantly increased from 32 Mm3/year (2003–2009) to 262 Mm3/year (2015–2021). This reflects the aquifer exposure for extensive water pumping to irrigate newly cultivated lands. The derived findings on the aquifers’ storage losses provide a vital source of information for the decision-makers to be employed for short- and long-term groundwater management.

Groundwater analysis using Gravity Recovery, Climate Experiment and Google Earth Engine: Bundelkhand region, India

India is one of the highest consumers of groundwater in the world. This precious resource is important for socio-economic development and it has been extremely rapidly depleting. Therefore, monitoring of groundwater storage (GWS) change is of great significance. Dependence on in-situ groundwater measurement for accurate assessment of regional-scale GWS changes is constrained, especially over extended durations, due to poor spatiotemporal coverage of in-situ measurement and uncertainty in the storage process. In present study, Gravity Recovery and Climate Experiment (GRACE), which offers quantitative measurement of terrestrial water storage (TWS) coupled with TerraClimate data, has been used to estimate the changes in GWS from 2002 to 2017 for the Bundelkhand region of Uttar Pradesh, India. Google Earth Engine and ArcGIS are the processing software employed to process and analyse the satellite data. It was observed that, on average GWS, has been depleted by 112 mm during the studied period. The highest GWS fluctuation was observed in 2012(-247 mm to –60 mm); the lowest fluctuation for year 2009, (−162 mm to −43 mm). Volumetric groundwater depletion in the study area was calculated using the average GWS depletion. There is a reduction of 1,12,000 m3 groundwater per unit square kilometre area over the period of 16 years, however, 3.29 × 109 m3 in the entire studied region. Because of the rugged topography and hard rock terrain, the recharge process is poor. The population of the area increased by 24%, or by a factor of two, throughout the research period.

Estimating the spatio-temporal assessment of GRACE/GRACE-FO derived groundwater storage depletion and validation with in-situ water quality data (Yazd province, central Iran)

Due to the lack of surface water availability in Yazd province, groundwater has been overexploited as a key source of water supply, resulting in the overexploitation of groundwater resources for agricultural activities. This study employed the data of the Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow-On (GFO) satellite to determine terrestrial water storage (TWS) and deriving groundwater storage (GWS) variations using global land data assimilation system (GLDAS) water storage components in Yazd province from 2003 to 2020. The time series results showed that the annual changes of GWS are positive from 2003 to 2007, and continue negative with a decrease in precipitation significantly causing depletion of GWS in the aquifers. The Pearson correlation coefficient is close to 0.58 between observed and GRACE-derived GWS on yearly basis and both show a decreasing GWS trend. The results of calculating the groundwater balance for aquifers showed that the renewable water resources have decreased from 786 to 250 million cubic meters (MCM) between the water year 2009–2010 and 2019–2020. This has caused the electrical conductivity (EC) to increase from about 8500 to 12,500 μS/cm. The correlation coefficient between EC and observed and GRACE-derived GWS was around −0.50 and −0.79, respectively. GRACE-derived and analytically calculated groundwater storage deficit (GSD) is around 2491 and 2775 MCM showing a similar downward trend. These results, while confirming GRACE-derived GWS, point out the need to revise the analytical calculation of the groundwater balance based on the unmodified aquifer domains and the non-uniform distribution of observation wells in most aquifers to reduce the difference between observed and GRACE-derived GWS anomalies.

Unstructured-grid approach to develop high-fidelity groundwater model to understand groundwater flow and storage responses to excessive groundwater withdrawals in the Southern Hills aquifer system in southeastern Louisiana (USA)

Study regionThe Southern Hills aquifer system (SHAS) in the Louisiana Capital Area Groundwater Conservation District (CAGCD), USA. Study focusThe SHAS provides abundant groundwater for public and industrial supplies in the CAGCD. Groundwater depletion, saltwater intrusion, and land subsidence are potential concerns due to prolonged excessive groundwater withdrawals. This study develops a high-fidelity groundwater flow model utilizing a complex unstructured grid to investigate groundwater flow and storage responses to excessive groundwater withdrawals for the SHAS in the CAGCD. The groundwater model incorporates the Mississippi River alluvial aquifer down to the Miocene sands extending to depths around 1 km. New hydrological insightsGroundwater modeling results indicate large cones of depression in the Evangeline and Jasper formations in the Baton Rouge area due to prolonged groundwater withdrawals. Low-permeability faults are inferred by significant groundwater level difference across the faults. While local groundwater storage depletion in deeper aquifers is evident, overall estimated groundwater storage changes of the SHAS in the CAGCD are close to zero in the past two decades, indicating insignificant groundwater storage changes. This is attributed to dominant interactions between the major rivers and the shallower alluvial aquifer. In addition, the simulated groundwater storage changes exhibit patterns similar to those derived by the Gravity Recovery and Climate Experiment (GRACE) model that has been used in evaluation of groundwater depletion in many regional studies.

GRACE Satellite-Based Analysis of Spatiotemporal Evolution and Driving Factors of Groundwater Storage in the Black Soil Region of Northeast China

Clarifying the evolution pattern of groundwater storage (GWS) is crucial for exploring the amount of available water resources at a regional or basin scale. Currently, the groundwater resources of Northeast China have been extensively exploited, but only limited studies have assessed the extent of GWS depletion and its driving mechanisms. In this study, the groundwater storage anomaly (GWSA) in the black soil region of Northeast China was explored based on the Gravity Recovery and Climate Experiment (GRACE) satellite combined with the Global Land Data Assimilation System (GLDAS) hydrological model. The results show that from 2002 to 2021, the overall GWSA decreased (−0.4204 cm/a), and specifically, the average rates of decrease in Heilongjiang, Jilin, and Liaoning Provinces were −0.2786, −0.5923, and −0.6694 cm/a, respectively, with the eastern, southern, and central parts of Heilongjiang, Jilin, and Liaoning Provinces losing seriously. Especially the GWSA deficit trend can reach −0.7471 cm/a in southern Jilin Province. The GWSA deficits in the three provinces from April to September were greater than 0.40 cm/a, while the deficit values from January to March and from October to December were less than 0.40 cm/a. This study is the first to quantitatively analyze the GWSA and its influencing factors in Northeast China for 2002–2021. The results of the study help clarify the differences in the spatial and temporal distribution of groundwater resources and their driving mechanisms in the northeastern black soil regions and provide a reference for the conservation and sustainable utilization of groundwater resources in the black soil region.

Inferring decelerated land subsidence and groundwater storage dynamics in Tianjin–Langfang using Sentinel-1 InSAR

ABSTRACT To meet the growing demand for socioeconomic development, a large amount of groundwater is extracted from confined aquifers worldwide. The North China Plain has experienced considerable groundwater depletion and subsidence during the past six decades. In this study, we use Sentinel-1A/B SAR images from 2015 to 2020 to map the ground subsidence of the Tianjin–Langfang area. Three subsiding zones centered at Guangyang, Wuqing–Bazhou, and Jinghai are identified with maximum subsidence rates of 98.1, 121.8, and 104.7 mm/yr. Seasonal and long-term signals are separated from time series subsidence and hydraulic measurements using continuous wavelet transform to retrieve aquifer parameters. The long-term subsidence, which fits well with an exponential decaying model, remarkably slows down in our study area. The elastic skeletal storage coefficients range between 0.52×10−3 and 9.66×10−3. We then retrieve the spatial–temporal variations of total groundwater storage, recoverable groundwater storage, and irreversible groundwater storage. Groundwater storage depletion rates are apparently reducing, which benefits from the operation of the South-to-North Water Transfer Project and local groundwater management practices.

A numerical assessment on the managed aquifer recharge to achieve sustainable groundwater development in Chaobai River area, Beijing, China

Intensive groundwater exploitation has depleted groundwater storage and led to a series of geo-environmental problems in Beijing Plain, China. Managed Aquifer Recharge (MAR) has been endorsed to mitigate the groundwater storage depletion and achieve groundwater sustainability. A pilot MAR has been tested in the Chaobai River catchment since 2015. An innovative large-scale MAR consisting of 9 cascade terraced infiltration ponds was proposed and its effectiveness was assessed in this study using an integrated modelling approach. The integrated model coupled the regional and local transient flow and transport processes. The transient regional flow model simulated historical groundwater level declines and storage depletion in the Beijing Plain from 1995 to 2018. The coupled regional and local flow model was used to simulate the pilot MAR test in the Chaobai River from 2015 to 2018. A significant groundwater level increase was observed nearby the pilot MAR since 2015. The transport model results indicate that approximately 40% of the infiltrated water was captured by pumping wells in the No.8 well field. The models were further used to assess the long-term effects of the large-scale MAR from 2020 to 2050. The simulation results show that the groundwater system will reach a new equilibrium state under the implementation of the large-scale MAR scheme. Almost 91% of the abstracted water in the No. 8 well field will come from the MAR infiltration. The proposed large-scale MAR is very effective in restoring the depleted aquifer storage and maintaining the groundwater abstraction in the No.8 well field. However, with the increase of the groundwater level, the infiltration rate of several ponds will decrease. Therefore, it is important to maintain a dynamic balance between artificial recharge and groundwater abstraction in order to achieve a sustainable long-term MAR operation in the region.

Methods for Characterizing Groundwater Resources with Sparse In Situ Data

Accurate characterization of groundwater resources is required for sustainable management. Due to the cost of installing monitoring wells and challenges in collecting and managing in situ data, groundwater data are sparse—especially in developing countries. In this study, we demonstrate an analysis of long-term groundwater storage changes using temporally sparse but spatially dense well data, where each well had as few as one historical groundwater measurement. We developed methods to synthetically estimate groundwater table elevation (WTE) times series by clustering wells using two different methods; a uniform grid and k-means-constrained clustering to create pseudo-wells. These pseudo-wells had a more complete groundwater level time history, which we then temporally and spatially interpolated to analyze groundwater storage changes in an aquifer. We demonstrated these methods on the Beryl-Enterprise aquifer in Utah, USA, where other researchers quantified the groundwater storage depletion rate, and the wells had a large number of historical measurements. We randomly used one measurement per well and showed that our methods yielded storage depletion rates similar to published values. We applied the method to a region in southern Niger where wells had only one measurement per well, and showed that our estimated groundwater storage change trend reasonably matched that which was calculated using GRACE satellite data.

Evaluating dynamics of GRACE groundwater and its drought potential in Taihang Mountain Region, China

The Taihang Mountain Region (TMR) of China is an important headwater area that provides substantial water resources supporting the social and ecological stability of the North China Plain. Currently, groundwater resources in the TMR are rapidly declining, but the degree of groundwater storage (GWS) depletion and the driving mechanism of groundwater drought remain poorly understood. This study combined the Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) datasets to thoroughly analyze GWS changes in the TMR and the dominant driving factors during 2003–2016. In addition, a new index—the groundwater drought potential index (GDPI)—was established to quantify the potential of groundwater drought. We found that GRACE-derived terrestrial water storage in the TMR experienced a significant reduction (-21.82 mm/yr, p < 0.01) during 2003–2016, with a similar reduction in GWS (-21.22 mm/yr, p < 0.01). Human-induced impacts exerted a decisive role in GWS decreases in this region, with a relative contribution rate of 96% compared to the climatic contribution (4%). Climatic impacts on GWS were primarily observed in the southeastern TMR, where climate change appeared to be unbeneficial to groundwater recovery and exacerbated local groundwater depletion. Specifically, the groundwater drought potential was entirely increasing, indicating a worsened climate condition that precipitation increasingly failed to fill the groundwater deficit. Actions should be taken urgently to address the local groundwater crisis and to maintain water security. Our proposed GDPI not only reflected the degree of groundwater depletion but also revealed the relationship between groundwater drought and precipitation, making the index capable of being applied in drought forecasting. This study delivers a new perspective to better understand the mechanisms of GWS change and groundwater drought, and the results are expected to provide a valuable reference for groundwater management and water sustainability goals.