Groundwater Variations Research Articles

Effects of geochemical and hydrodynamic transiency on desorption and transport of As in heterogeneous systems

Spatial and temporal variations in groundwater As concentrations are mainly caused by changes in geochemical and hydrodynamic conditions. In this study, the effects of geochemical and hydrodynamic transiency on As desorption and transport in a layered heterogeneous system with preferential flow paths during continuous or intermittent water extraction were investigated. A flume desorption experiment was performed after an adsorption experiment lasting 99 d with competitive adsorption anions (phosphate) in the influent. The results indicated that although competitive adsorption between As and phosphate at the water/solid interface significantly promoted As desorption from solid materials, marked amounts of As desorbed slowly or were on irreversible sorption sites in the system. As adsorbed by the sand and clay near the preferential flow paths was preferentially released, while the release of As from the interiors of the clay zones was limited by diffusion. Water extraction accelerated As transport between the different layers, and this increased the overall rate of As release from zones limited by diffusion. Desorption rate of As in the layered system was fast initially, followed by a period of slow desorption rate that lasted months. The desorption hysteresis was due to slow desorption controlled by diffusion. The results provide important insights for understanding and modeling As desorption and transport in field systems.

Comparison of the shallow groundwater storage change estimated by a distributed hydrological model and GRACE satellite gravimetry in a well-irrigated plain of the Haihe River basin, China

Groundwater is a key component of the global hydrological cycle. Quantitative approaches to estimate the spatial and temporal changes in groundwater storage (GWS) could provide solid foundation for sustainable management. This study made a comprehensive comparison of GWS changes based on two independent approaches: the Soil and Water Assessment Tool (SWAT) hydrological model and Gravity Recovery and Climate Experiment (GRACE) satellite mission data. The feasibility of using these two estimation methods to quantify shallow groundwater variations in the Haihe River basin of China, a globally representative overexploited area, was assessed. The GRACE-derived GWS changes were calculated based on independent component analysis and a joint inversion method. The results showed that the GRACE-estimated shallow GWS anomalies during 2003–2012 agree well with the SWAT-simulated data. For the variations in the long-term GWS depletion rate, we found that heterogeneity at 22 subbasin (approximately 500 to 1500 km2) scales was detected by the GRACE data, and these results were spatially coherent with the SWAT simulations based on the distributed modeling units and multiple inputs. The GRACE estimates could adequately replicate the general trends of GWS depletion in the winter wheat (Triticum aestivum L.) growth period and recovery in the summer maize (Zea mays L.) growth period. Specifically, comparisons between GRACE-based and SWAT-simulated results indicated that the signals of pumping for winter wheat irrigation in several key water requirement periods in April, May and November were identified by GRACE, as were seasonal changes in shallow GWS (e.g., an obvious depletion in spring). Despite an overestimation of the scope of the fluctuations in GRACE estimates compared with those of SWAT simulations from the perspective of the water flux, the effective identification of the impact of anthropogenic exploitation on shallow GWS in GRACE suggests that this monitoring tool could be applied in the groundwater management of this plain. This study demonstrated a good agreement between SWAT-simulated and GRACE-based shallow GWS changes from the perspectives of long-term trends and variations in crop seasons. Additionally, satisfactory consistency was observed from the perspective of the water flux in this semiarid and semihumid study region considering the influence of human activities.

Groundwater simulation in Dak Lak province based on MODFLOW model and climate change scenarios

PurposeGroundwater plays a critical part in both natural and human existence. When surface water is scarce in arid climates, groundwater becomes an immensely valuable resource. Dak Lak is an area that frequently lacks water resources for everyday living and production, and the scarcity of water resources is exacerbated during the dry season. As a result, it is critical to do study and understand about groundwater to meet the region's water demand. This study aims to extend the use of the MODFLOW model for groundwater simulation and assess the overall groundwater reserves and water demand in the highland province Dak Lak.Design/methodology/approachThe MODFLOW model is used in this work to compute and analyze the flow, prospective reserves of groundwater from which to plan extraction and estimate groundwater variation in the future.FindingsThe application of the MODFLOW model to Dak Lak province demonstrates that, despite limited data, particularly drilling hole data for subterranean water research, the model's calculation results have demonstrated its reliability and great potential for use in other similar places. The use of the model in conjunction with other data extraction modules is a useful input for creating underground flow module maps for various time periods. The large impact of recharge and evaporation on groundwater supplies and water balance in the research area is demonstrated by simulations of climate change scenarios RCP4.5 and RCP8.5.Originality/valueNone of the studies has been done previously to analyze water resources of Dak Lak and the scarcity of water resources is exacerbated during the dry season. Therefore, this study will provide useful insights in the water resource management and the conservation of Dak Lak. The groundwater in Dak Lak can meet the area's water demand, according to the results obtained and water balance in the study area. However, the management of water resources and rigorous monitoring of groundwater extraction activities in the area should receive more attention.

Multi-objective optimization of the coastal groundwater abstraction for striking the balance among conflicts of resource-environment-economy in Longkou City, China

Rational coastal groundwater planning is of great significance to freshwater supply for sustainable social-economic development, and to environmental protection in case of seawater intrusion (SI). Quantifying the relation among groundwater quality, quantity, and the related social-economic benefits in a coastal region with intense spatio-temporal variation in groundwater abstraction is helpful to the restoration of the coastal aquifer, and the practical policymaking. However, due to the comprehensive reality involving interdisciplinary principles, it is usually difficult to integrate all the main attributes of groundwater resources into a mono-policymaking process, which might lead to biased decisions, producing a series of adverse impacts on the environment and the social economy. This study thereby develops a combined simulation-optimization model (S-O model) in the coastal part of Longkou City, China, for striking the balance among the three main attributes of groundwater, i.e., the groundwater quantity, groundwater quality or its environmental function, and its related economic yield involving the agricultural and industrial sectors. It is seen that the industrial sector contributed over 80% of the economic yield by consuming over 10% of the total groundwater resource, and the massive agricultural use of groundwater was mainly responsible for the SI. The results of the multi-objective optimization provided practical alternative schemes for groundwater abstraction in terms of maximizing economic yield and minimizing SI. Moreover, the decision discrepancy caused by partial management only considering the groundwater quantity and quality would lower the water use efficiency, and then cause unacceptable economic losses for the enterprises and the government. Our research highlights that the interdisciplinary management of groundwater resources based on the S-O model could significantly improve practicability in groundwater policymaking, and provides a typical reference for the other developing regions facing difficulty in groundwater management during coastal urban planning and economic transformation.

Fluoride contamination, spatial variation, and health risk assessment of groundwater using GIS: a high-density survey sampling in Weifang City, North China.

The present study, with the aid of GIS, utilizes high-density groundwater (GW) sampling data (1398 samples) to analyze the spatial variation characteristics of GW fluoride in Weifang City (WFC), and evaluate the health risks associated with drinking water routes. The concentration of fluoride in the GW of WFC is observed to be between 0.08 and 9.16mg/L, with a mean value of 0.62mg/L. The fluoride concentration of a total of 192 GW samples exceeded the limit of China's GW quality standards (1mg/L), accounting for 14.74%. The GW fluoride concentration in most areas of WFC is less than 1mg/L. However, the relatively high-value zones are mostly concentrated in the upper reaches of Wen River, the east of Shouguang, the southeast of Anqiu, the east of Qingzhou, the east of Fangzi, and the southeast and northwest of Gaomi. The hydrochemical types of GW in WFC are mostly HCO3-Ca·Mg and SO4·Cl-Ca·Mg, while GW samples with hydrochemical types HCO3-Na and SO4·Cl-Na are characterized by high fluoride content. The hydrochemical characteristics of GW in WFC are mostly dominated by rock weathering. In addition, the northern coastal plain is evidently influenced by seawater intrusion. The concentration of fluoride in GW is affected by the dissolution of fluorine-containing minerals, cation exchange, and alkaline environmental factors. The effect of GW by seawater intrusion and very high content of Na+ will decrease the fluoride content of the GW through cation exchange. Health risk assessment demonstrated that the mean values of non-carcinogenic hazard quotient (HQ) for infants, children, teenagers, and adults were 0.52, 0.35, 0.31, and 0.30, respectively. In addition, the distribution characteristics of GW fluoride in high health risk areas (HQ > 1) in WFC are further consistent with the spatial variation of GW fluoride content. Overall, the health risk distribution area of GW fluoride in WFC is decreasing in the following order: infants > children > teenagers > adults.

Isotopic signatures to address the groundwater recharge in coastal aquifers

The dynamics of the coastal aquifers are well-expressed by geochemical and isotopic signatures. Coastal regions often exhibit complex groundwater recharge pattern due to the influence of depression in the Bay of Bengal, tidal variations on surface waters, saline water intrusion and agricultural return flows. In this research, groundwater recharge processes occurring in coastal Tamil Nadu, South India were evaluated using major ion chemistry and environmental isotopes. A total of 170 groundwater samples were collected from shallow and deep aquifers during both post-monsoon (POM) and pre-monsoon (PRM) seasons. The isotopic results showed a wide variation in the shallow groundwater, suggesting contribution from multiple recharge sources. But, the deeper groundwater recharge is mainly from precipitation. The northern part of the study area showed more depleted isotopic values, which rapidly changed towards south from −6.8 to −4.4‰. Alternatively, central and southern parts exhibited relatively enriched isotopic content with variation from −0.58 to −2.7‰. Groundwater was discerned to be brackish to saline with chloride content, 600–2060 mgL−1 and δ18O ranging from −5.8 to −4.5‰, suggesting influence of the saline water sources. A minor influence of anthropogenic activities was also observed in the deeper groundwater during PRM, which was confirmed by tritium and Cl− trends. The old groundwater with depleted isotopic content infer recharged by distant sources while modern groundwater with enriched isotopes points to the influence of evaporated recharge.

Three (3D) dimension model of settlement differences of the clay ground under rigid foundation by the affection of the groundwater variations – A comparison

In recent decades, settlement differences of the Clay ground implemented in areas and countries in the world. Whereas marine clay ground behaviors under Rigid foundation to build the construction on the clay ground with marine clay origin was evaluated the different methods such as Field and experimental measuring method, Finite Element method, formulas or TERZAGHI method and so on. Moreover, the influence of the groundwater levels is one of the most quite important problems to be needed considering. The object of this paper uses Standard Penetration (SPT), Unconfined Compression Test, and TERZAGHI formula, groundwater effects, and simulation by the software for measuring the vertical displacement (or settlement differences) of the rigid foundation on marine clay origin ground at Vinh Quang ward, Rach Gia town, Viet Nam. Results of the paper described clearly for settlement differences (vertical displacement) of the Rigid foundation as building loading with a comparison between Field, experimental, and software simulation so it can consult effectively for design and doing construction works in Civil and Geology Engineering.

Hydro-geochemical autographs, attribute indicators and health threat evaluation of Fluoride and Ironic elements variability in ground water in Abuja North-central Nigeria

Tap water from twenty-five houses using private water sources, in an area of ironic and fluoride mineralization (Abuja, Nigeria), was evaluated so to ascertain the extent of conformity with chemical clean water quality criterions, and how this is inspired through householder water treatment resolutions. The percentage of analyses surpassing water quality criteria were high, with 67% of tap water samples above one or more chemical criterions. The greatest exceedances for health-established criterions were iron (44%) and fluoride (40%). The concentration of iron in borehole water varied at different sites, between 0.01 mg/L and 2.95 mg/L with an average value of 1.02 mg/L while that of fluoride ranged from 0.47 mg/L to 1.84 mg/L with an average value of 1.28 mg/L. The Hierarchical cluster analysis revealed three common clusters in which the samples may be grouped. The carcinogenic threat was calculated with defined procedures by USEPA considering ingesting and dermal pathways. The CDI values for iron and fluoride varied from 6.80E-04 to 0.20 and 8.33E-02 to 0.12 for children, while adults’ index was 9.17E-04 to 1.56E-02 and 5.56E-02 to 1.44E-02, respectively. For Total Threat Index (TTI), adults and children are below 1.0 for both iron and fluoride in all the examined locations.

Analytical Solution for Tide-Influenced Groundwater Variation along Sloping Complex Coastal Aquifer in Presence of Rainfall Infiltration

AbstractCoastal regions have the most challenging aquifer systems because of their geometry and the flow behavior of groundwater with tidal oscillations. Studies have focused on tide-induced ground...

Groundwater quality and availability assessment: A case study of District Jhelum in the Upper Indus, Pakistan

People's well-being and their economic development are linked to the availability and accessibility of water. The Pind Dadan Khan tehsil located on the right bank of River Jhelum is a classic example of water stressed confronting water quality and quantity issues. To evaluate usable potential and qualitative variations of groundwater, an integrated approach involving geophysical, water quality and risk assessment techniques was used. Accordingly, groundwater potential zones were categorized. A small shallow fresh groundwater pocket with acceptable water quality (<1.5 dS/m) for a depth between 15 m to 50 m exists in the eastern part of the study area. The groundwater of remaining tehsil was highly saline (TDS: 3852.23±5091.54 mg/L with maximum level up to 23164.03 mg/L). The quality of domestic wells at these 82 sites was unsafe (90%) due to salts, bacteriological contamination (71%), fluoride (45%), arsenic (5%), and nitrate (4%). Compared to these, public water supply schemes show comparatively lower salts (total dissolved solids of 144-2690 mg/L). However, arsenic was found beyond the WHO Drinking water guidelines (10 µg/L) in 65% sources which may pose serious cancer risks for 2 to 5 persons (maximum 12 persons) per 10,000 population.The study reveals that the freshwater in the study area is scarce and of vulnerable quality and require integrated water quantity and quality management. Our results also suggest that in arid to semi-arid regions, scoring factors based on salinity levels and relative size of the saline zone should be incorporated into indicators of water access and availability.

Human health risk evaluation of sodium and ironic elements variability in ground water: A case study of Abuja North, Nigeria

Harmful substance tends to come into water bodies through geodesic and human-induced sources, therefore persistent drinking water monitoring schemes are crucial. The goal of this paper was to estimate the human health threat posed through high sodium and iron accumulation in borehole water used for both consumption and domestic activities. As this will help in the prevention of water-related sicknesses and maintenance of good health for human being that rely on water to survive. Specially, rural region need to be enlightened about biochemistry of the mineral elements ingested, since excessive intake of some minerals can upset homeostatic balance and cause toxic side effects. For instance, excess sodium ingestion ensuing from daily intake of saline origins is associated with high blood pressure, while excess iron intake can stimulate liver impairment or brain damage which connected to aging and protein-misfolding neurodegenerative ailments. More importantly, when an individual suffering from a chronic sickness take prescriptions with water of unknown quality as human being believes that groundwater possess safe water quality, the health situation becomes worst. In this paper, iron accumulation in borehole water varied at distinct sites, span between 0.01 mg/L and 2.95 mg/L with a mean value of 1.02 mg/L whereas that of sodium range from 55.98 mg/L to 515.45 mg/L with mean value of 260.19 mg/L. The Hierarchical cluster scrutiny revealed three common clusters wherein the samplings could be grouped. The non-carcinogenic threat was calculated and the Total Threat Index above 1.0 for sodium ingestion in the scrutinized sites was gotten from all locations.

Reconstructing groundwater storage variations from GRACE observations using a new Gaussian-Han-Fan (GHF) smoothing approach

This study focuses upon development of a new filter, referred to as Gaussian-Han-Fan (GHF) filtering, and its application within a comprehensive procedure for estimating groundwater changes. The Canadian Prairies was the study area. Variations in groundwater were estimated by using 15 years of Gravity Recovery And Climate Experiment (GRACE) twin-satellite observations (April 2002 to June 2017). Surface water storage (sum of soil moisture, snow water equivalent, canopy water, and surface water bodies) was subtracted from reconstructed GRACE-based Terrestrial Water Storage (TWS) changes through GHF filtering. To estimate the required hydrological parameters, both the Global Land Data Assimilation System (GLDAS) and Water Global Hydrology Model (WGHM) were used and evaluated. Water level changes for major surface water bodies were estimated using satellite altimetry-based products. The monthly average of GWS variations over the Prairies ranged between −200 mm and +230 mm. A positive trend was found for both TWS and GWS variations, with the highest values in the region surrounding Hudson Bay, particularly in northern Manitoba (about 55 mm/year). Estimated GWS anomalies error was equivalent to about 10% of its absolute value, with a mean of 19 mm. GWS variations results were validated using 116 active in-situ groundwater level measurements in five different river basins (Peace-Athabasca, Churchill, North Saskatchewan, South Saskatchewan, Missouri), which were all located in Alberta (Canada). Good agreement was achieved in each river basin (correlation > r = |0.70|, P < 10−4, RMSE < 55 mm). Regardless of hydrological system (GLDAS or WGHM), better statistical metrics were found when the average of the five basins was considered (r > |0.90|, P < 10−4), with lowest errors (RMSE or UnRMSE < 30 mm).

Spatiotemporal variation and periodic evolution characteristics of groundwater in the Xining area of China, eastern Qinghai–Tibet Plateau

As an important water source, groundwater profoundly influences global human survival and production. The spatiotemporal characteristics of groundwater and the periodic variation law of different time scales must be analyzed to understand the dynamic situation of this resource and to provide scientific guidance for its rational utilization and management. In this study, the temporal and spatial variability and periodicity of groundwater level in the Xining region of eastern Qinghai–Tibet Plateau in China were studied using the traditional statistical method, geographic information system, and Morlet wavelet analysis. Results show that the groundwater dynamics in the study area are mainly controlled by three factors, namely, the amount of river water infiltration, discharge from groundwater, and artificial exploitation. These factors can be divided into three dynamic types, namely, hydrological, hydrological exploitation, and runoff discharge, according to their combination relationship. From 1980 to 2020, the groundwater depth in Xining initially increased before stabilizing and eventually decreasing. As revealed in the spatial variability analysis, groundwater depth demonstrates a huge spatial difference with a moderate spatial variation intensity across different periods. Moreover, the spatial correlation of groundwater in the abundant season is lower than that in the dry season mainly due to increasing artificial exploitation. Meanwhile, the Kriging interpolation of the spherical model in the geographic information system reveals that the groundwater in Xining is deep in the south and east and shallow in the north and west. From the 1960s to 2000s, the inter-annual groundwater in the region continuously declined due to chronic overexploitation, with a maximum cumulative depth of 15 m. Afterward, the amount groundwater extraction was further reduced, and the amount of rainfall significantly increased in recent years. Accordingly, the cone of depression underwent an evolutionary process involving periods of expansion, stability, and shrinkage. The annual groundwater level in most monitoring wells within the study area demonstrated the same multi-year scale time-variation characteristics with an evident regular periodic variation on the 9-14a and 17-25a time scales according to the results of the Morlet wavelet transform analysis. The temporal sequence of groundwater from 1980 to 2020 had two main periods, namely, 12a and 21a. According to these time scales, the groundwater level in Xining will continue to increase in the short term, which provides a scientific theoretical basis for the long-term sustainable development of groundwater resources and government decision-making.

Comparative Study of Groundwater-Induced Subsidence for London and Delhi Using PSInSAR

Groundwater variation can cause land-surface movement, which in turn can cause significant and recurrent harm to infrastructure and the water storage capacity of aquifers. The capital cities in the England (London) and India (Delhi) are witnessing an ever-increasing population that has resulted in excess pressure on groundwater resources. Thus, monitoring groundwater-induced land movement in both these cities is very important in terms of understanding the risk posed to assets. Here, Sentinel-1 C-band radar images and the persistent scatterer interferometric synthetic aperture radar (PSInSAR) methodology are used to study land movement for London and National Capital Territory (NCT)-Delhi from October 2016 to December 2020. The land movement velocities were found to vary between −24 and +24 mm/year for London and between −18 and +30 mm/year for NCT-Delhi. This land movement was compared with observed groundwater levels, and spatio-temporal variation of groundwater and land movement was studied in conjunction. It was broadly observed that the extraction of a large quantity of groundwater leads to land subsidence, whereas groundwater recharge leads to uplift. A mathematical model was used to quantify land subsidence/uplift which occurred due to groundwater depletion/rebound. This is the first study that compares C-band PSInSAR-derived land subsidence response to observed groundwater change for London and NCT-Delhi during this time-period. The results of this study could be helpful to examine the potential implications of ground-level movement on the resource management, safety, and economics of both these cities.

GRACE-based estimates of groundwater variations over North America from 2002 to 2017

GRACE-based estimates for groundwater storage (GWS) changes in North America substantially depend upon correction of glacial isostatic adjustment (GIA) effects, which are usually removed with GIA models. In this study, GIA effects are eliminated by employing an independent separation approach with the aid of Global Navigation Satellite System (GNSS) vertical velocity data. Our goal is to provide an independent estimate for monthly GWS changes within North America in 1-degree-grids and their trends over the whole GRACE mission lifetime from April 2002 to June 2017. This estimate is derived from the release-6 version of GRACE monthly level-2 data, GNSS data, land surface models for soil moisture and snow water equivalent, and satellite altimetric lake level data. We find a GWS anomaly in form of an increasing trend in Saskatchewan, which affects the Saskatchewan Province and the states of Montana, North Dakota and Minnesota, and 4 GWS anomalies with declining trends in Nevada, California, Arizona and Texas, respectively. The monthly changes of these GWS anomalies, except for the one in Nevada, are validated by well level data. We provide results for average monthly GWS changes and the trends for the 5 anomalies but also in separate form for the 13 affected states or provinces. The increasing trends of the Saskatchewan GWS anomaly and the affected 3 states are related to increasing precipitation and can be elucidated by the decreasing drought intensity level. On the contrary, the declining trends in GWS can be explained by weakening precipitation and are mostly supported by the increasing drought intensity level in the other 4 anomalies and the affected states, which are Nevada, California, Arizona, New Mexico, Texas, Oklahoma, Kansas, and Colorado. Our estimates of monthly GWS changes and their trends can serve as alternative and beneficial input for the sustainable management of groundwater resources in North America.

Hydrochemical Characteristics of Groundwater at the Epicenter of the 2021 Biru M6.1 Earthquake in Central Tibet

Groundwater is undoubtedly important for water security and eco-environmental protection, especially in areas that experience earthquakes. Analyzing the characteristics and variation of groundwater after an earthquake is significant to obtain a better understanding of the seismic risk and rational management of groundwater resources. This study investigated the hydrogeochemical characteristics of groundwater at the epicenter of the 2021 Biru M6.1 earthquake in central Tibet, southwest China, using 23 water samples. The results showed that: (1) the hydrochemical type, hydrogen and oxygen isotope ratios, and SiO2 concentrations of three hot spring water samples in the study area were significantly different from those of samples taken elsewhere, indicating that the hot spring water originates from deeper geothermal reservoirs and has undergone more distant migration and longer fractionation processes; (2) the geochemical characteristics of groundwater from some sampling sites in the epicentral area were apparently distinct from those of other shallow groundwater or surface water samples, suggesting that the groundwater environment in the epicentral area has been affected by the earthquake. Along with the macroscopic groundwater responses in the epicentral area after the earthquake, we investigated the influencing mechanisms of the earthquake on the regional groundwater environment. We conclude that a shorter distance from the epicenter to the seismogenic fault leads to a greater possibility of the generation of new fractures, which then induce macroscopic responses and chemical characteristic variations for groundwater.

Spatial earthquake vulnerability assessment by using multi-criteria decision making and probabilistic neural network techniques in Odisha, India

In this study, the multi-criteria decision-making method was used to estimate the weights of several input factors such as slope, curvature, elevation, proximity to road, road density, proximity to land use, land use density, proximity to water bodies, river density, rail density, distance from rail, groundwater variation, lithology with amplification factors, peak ground acceleration (PGA) variation, and population density. An integrated analytic hierarchy process (AHP) and a probabilistic neural network (PNN) were applied for the Earthquake vulnerability assessment (EVA). The PNN model successfully explored the relationship between variables and weights obtained from the AHP approach. Validation results indicate that 92.5% accuracy was attained by the PNN model. According to the results, 24.26%, 15.26%, and 20.58% of the area fall under very-high, high, and moderate vulnerability category, respectively. The EVA map illustrates that high to very-high impact could be observed in coastal Odisha and few districts in the Mahanadi Graven.

In-situ pumping tests and numerical simulations of seepage wells in the Yellow River valley, China

Abstract Seepage wells that can convert surface water into groundwater are often constructed near river valleys to obtain more water and lead to smaller drawdown compared with traditional wells. Seepage wells have been widely used, whilst the groundwater and river-level variations caused by seepage wells are still unclear, and numerical models are rarely verified due to the lack of in-situ observational data, which may lead to results that are quite different from the actual conditions. To address those limitations, a large-scale pumping test was carried out near the Yellow River valley in China and a coupled seepage–pipe flow model was established using the exchange yield between the aquifer and pipe as the coupling key in this research. The coupled model was evaluated with in-situ measurement. The field observation showed that both the river and groundwater had a positive response to the pumping of the seepage wells. The simulation results indicated that our model can well estimate the pumping rate and drawdown with root-mean-square deviations of 158.235 m3/d and 0.766 m, respectively. Further, it is also found that the groundwater showed the obvious characteristics of three-dimensional flow under the influence of seepage wells and the maximum drawdown should be less than 15 m to ensure exploitation efficiency. These findings provide important information that can guide the design and construction of seepage wells to improve the rational exploitation of groundwater.

Long-term and seasonal variation in groundwater storage in the North China Plain based on GRACE

The over exploitation of groundwater has seriously restricted the healthy development of social economy in North China Plain (NCP). The study of the change in the groundwater storage at different time scales is helpful to understand the characteristics of groundwater dynamic changes and real-time groundwater management. Based on Gravity Recovery and Climate Experiment (GRACE) satellite products and Global Land Data Assimilation System (GLDAS) data, this paper analyses the seasonal and long-term trend changes of NCP groundwater storage from June 2003 to June 2017 by using adaptive Ensemble Empirical Mode Decomposition (EEMD) algorithm. Moreover, their relationships with precipitation and the South-to-North Water Diversion Middle Route Project (SWDP) are analysed. The main conclusions are as follows: (1) The change of groundwater storage in NCP mainly shows a long-term downward trend and the downward trend gradually increases from northeast to southwest, and the maximum decline rate appears in Handan, reaching 26.44 mm/yr; (2) The main spatial pattern in the seasonal variation of groundwater storage in the NCP has a good consistency and the response of seasonal groundwater variation to seasonal precipitation variation lags by 3–4 months; and (3) After implementing the SWDP, the long-term decline rate of groundwater storage is reduced and the average contribution rate of seasonal variation characteristics of groundwater storage increases from 20% to 28%. The research results of this paper are helpful to understand the dynamic change process of groundwater storage and lay a foundation for further exploring the reasons for the change of groundwater storage.

District-scale numerical analysis of settlements related to groundwater lowering in variable soil conditions

This study presents a novel framework in which numerical modelling contributes to the performance of district-scale, subsidence-induced damage assessment in cities where ground settlements affect entire quarters. Therein, the implementation of expeditious procedures offers geotechnical engineers the possibility of contributing beyond the typical site scale. For this purpose, several “typified” hydro-geomechanical-loading (HGL) models, which represent (simplified) scenarios of masonry buildings undergoing settlements, were set up to account for different predisposing or triggering factors (i.e., soil heterogeneity, loading conditions, and groundwater variations) of settlement occurrence in built-up areas. These models exploit multi-source, wide-area input datasets encompassing the hydro-mechanical properties of geomaterials, in situ investigations and measurements (e.g., groundwater levels in wells), and innovative remote sensing data (i.e., DInSAR techniques). With reference to a district in Rotterdam City (the Netherlands), which was built on “soft soils”, the numerical simulations of different scenarios (i) provide an overview of the comparative role of predisposing or triggering factors on settlement occurrence and (ii) allow assessments of the expected induced damage to masonry buildings over 30 years with the exploitation of fragility curves. Considering the widespread diffusion of such geohazards, the proposed approach could help prioritise (rather expensive) maintenance work to the built heritage within sustainable strategies for subsidence risk mitigation.