Search Results (16)

Groundwater storage refers to the water stored in the pore spaces of underground aquifers, which has been increasingly affected by both climate change and anthropogenic activities in recent decades. Therefore, monitoring their changes and the factors that affect it is of great importance. Although the influence of natural factors on groundwater is well-recognized, the impact of human activities, despite being a major contributor to its change, has been less explored due to the challenges in measuring such effects. To address this gap, our study employed an integrated approach using remote sensing and the Google Earth Engine (GEE) cloud-free platform to analyze the effects of various anthropogenic factors such as built-up areas, cropland, and surface water on groundwater storage in the Lake Urmia Basin (LUB), Iran. Key anthropogenic variables and groundwater data were pre-processed and analyzed in GEE for the period from 2000 to 2022. The processes linking these variables to groundwater storage were considered. Built-up area expansion often increases groundwater extraction and reduces recharge due to impervious surfaces. Cropland growth raises irrigation demand, especially in semi-arid areas like the LUB, leading to higher groundwater use. In contrast, surface water bodies can supplement water supply or enhance recharge. The results were then exported to XLSTAT software2019, and statistical analysis was conducted using the Mann–Kendall (MK) non-parametric trend test on the variables to investigate their potential relationships with groundwater storage. In this study, groundwater storage refers to variations in groundwater storage anomalies, estimated using outputs from the Global Land Data Assimilation System (GLDAS) model. Specifically, these anomalies are derived as the residual component of the terrestrial water budget, after accounting for soil moisture, snow water equivalent, and canopy water storage. The results revealed a strong negative correlation between built-up areas and groundwater storage, with a correlation coefficient of −1.00. Similarly, a notable negative correlation was found between the cropland area and groundwater storage (correlation coefficient: −0.85). Conversely, surface water availability showed a strong positive correlation with groundwater storage, with a correlation coefficient of 0.87, highlighting the direct impact of surface water reduction on groundwater storage. Furthermore, our findings demonstrated a reduction of 168.21 mm (millimeters) in groundwater storage from 2003 to 2022. GLDAS represents storage components, including groundwater storage, in units of water depth (mm) over each grid cell, employing a unit-area, mass balance approach. Although storage is conceptually a volumetric quantity, expressing it as depth allows for spatial comparison and enables conversion to volume by multiplying by the corresponding surface area. Full article

The characterization of a groundwater body involves the construction of a conceptual model that constitutes the base knowledge for monitoring programs, hydrogeological risk assessment, and correct management of water resources. In particular, a detailed geological and geophysical approach was applied to define the alluvial Caronia Groundwater Body (CGWB) and to reconstruct a hydrogeological flow model. The analysis of the CGWB, located in north-eastern Sicily, was initially approached through a reanalysis of previous stratigraphic (boreholes) and geophysical (vertical electrical soundings and seismic refraction profiles) data, subsequently integrated by new seismic acquisitions, such as Multichannel Analysis of Surface Waves (MASW) and horizontal-to-vertical seismic ratio (HVSR). The analysis and reinterpretation of geoelectrical data allowed the construction of a preliminary 3D resistivity model. This initial modeling was subsequently integrated by a geophysical data campaign in order to define the depth of the bottom of the shallow CGWB and the thickness of alluvial deposits. Finally, a preliminary mathematical model flow was generated in order to reconstruct the dynamics of underground water. The results show that integration of multidisciplinary data represent an indispensable tool for the characterization of complex physical systems. Full article

Geological heterogeneity impacts groundwater flow patterns, necessitating a detailed hydrogeological framework for conceptualization process of aquifer systems. This research developed a new conceptual model of detailed geologic geometry by integrating 133 well-logs, 366 hydrodynamic data and 118 water samples. As new results, systematic 3D log correlation detected four distinct hydrostratigraphic units in the Southern Nyírség–Hajdúság Groundwater Body (East Hungary). The primary aquifer was identified as an incised valley 10–13 km wide and a NE–SW strike. Logan’s approach estimated the average hydraulic conductivity of the Incised Valley Unit (IVU) at 11 m/d, higher than the other three aquifers (3.2 m/d to 4.6 m/d). The average specific capacity of wells screening the IVU is 315.6 m³/d/m, in contrast with the remaining aquifers ranging from 31.6 m³/d/m to 92 m³/d/m. Pressure–depth profiles, dynamic pressure increment and hydraulic head maps revealed recharge–discharge zones and hydraulic windows between hydrostratigraphic units. The elongated pattern on the hydraulic head map at the depth of the IVU showed the existence of a preferential path along its axis within the mapped borders of the IVU. Hydrochemical analysis revealed Ca-Mg-HCO₃ water type within the primary aquifer and Na-HCO₃ water type in the laterally connected aquifer. The saturation index values indicated a transition from undersaturated to supersaturated state inside the main aquifer for calcite and dolomite minerals. The correlation matrix and PCA results demonstrated that the carbonate weathering process is the main factor controlling the groundwater chemistry. This integrated approach holds significance for future applications of the regional conceptual model in water management planning, sustainable aquifer development and contaminant transport modelling. It provides essential contributions to informed decision-making and the formulation of effective strategies, ensuring the long-term availability and utilization of groundwater resources. Full article

With increasing exploitation of groundwater resources and implementation of various activities in their recharge areas, it is vital to conduct a comprehensive assessment of aquifers to ensure their conservation and sustainable management. In the present study, we used a comprehensive approach to conceptualise and identify the functioning of two connected aquifer systems in north-eastern Slovenia: the Quaternary porous aquifers Dravsko polje and Ptujsko polje. The study presents the conceptual models of both aquifers and their interconnectedness using separate mathematical-numerical models with the aim of ensuring an integrated management of these alluvial aquifer systems. It also highlights the importance of understanding connections between such systems for simulating groundwater flow and transport of different contaminants. To describe the entire aquifer system, the study defines its three essential elements: the geometry of the aquifers, their recharge by precipitation, and other boundary conditions. The geometry of the Quaternary aquifers was defined using Sequential Indicator Simulation (SIS) with the ESRI’s ArcMap software. Next, LIDAR was used for determining their surface geometry. The hydrogeologic model was designed using the Groundwater Modelling System (GMS) developed by AQUAVEO. We used the MODFLOW 2000 calculation method based on the finite difference method (FDM). The model was calibrated with the PEST module, which was used to calibrate hydraulic conductivity and hydraulic heads between the measured and modelled data. Finally, the model was validated using the Nash–Sutcliffe (NSE) efficiency coefficient. In addition, the model results estimated using the PEST tool were validated with the hydraulic conductivities determined at the pumping sites (pumping tests), each belonging to water protection zones that define the maximum travel time of the particles. This was performed using the MODPATH method. The paper also presents the possibility of modelling heterogeneous but interdependent aquifers in a groundwater body. Modelling the connection between the two aquifers, which are the most important ones in the region, is essential for a comprehensive management of the entire system of water resources. The models allow for a better understanding of groundwater flow in both aquifers. Moreover, their interconnectedness will be used for further studies in this field, as well as for integrated water management. Full article

Wuhan and its surrounding areas have obvious geothermal spring outcrops, which are unexplored potential geothermal resources. The degree of geothermal resource development in Wuhan is low, and there is a lack of systematic research on their hydrochemical characteristics and formation mechanism. The Wuhan area is bounded by the Xiang-Guang fault, the South Qinling-Dabie orogenic belt in the north, and the Yangtze landmass in the south, with Silurian and Quaternary outcrops and little bedrock outcrops. The Silurian is the main water barrier in the region, which separates the upper Triassic and Paleogene as shallow aquifers and the lower Cambrian and Ordovician as deep aquifers. Different strata are connected by a series of fault structures, which constitute Wuhan’s unique groundwater water-bearing system. Eleven geothermal water (23~52 °C) and six surface water samples (around 22 °C) were collected from the study area. The geothermal water in the study area is weakly alkaline, with a pH of 7.04~8.24. The chemical type of geothermal water is mainly deep SO₄²⁻ with a higher TDS and shallow HCO₃⁻ type water with a lower TDS. Isotopic analysis indicates that atmospheric precipitation and water-rock interaction are the main ionic sources of geothermal water. The chemical composition of geothermal water is dominated by ion-exchange interactions and the dissolution of carbonates and silicates. The characteristic coefficients, correlation analysis, water chemistry type, recharge elevation, geothermal water age, reservoir temperature, and cycle depth were also analyzed. The performance was similar in the same geothermal reservoir, which could be judged as an obviously deep and shallow geothermal fluid reservoir, and the genetic conceptual model of Wuhan geothermal was preliminarily deduced. DXR-8 and DXR-9 had the best reservoir conditions, hydrodynamic conditions, rapid alternation of water bodies, and large circulation depth, which is a favorable location for geothermal resource development and will bring considerable economic and social benefits. Full article

Stacked phosphogypsum (PG) can not only cause a waste of resources but also has a serious negative impact on the surface environment. Phosphogypsum backfilling (PGB) in the underground goaf is a useful approach to effectively address the PG environmental problems. However, the effects of this approach on the groundwater environment have not been studied. Therefore, the present study aims to assess the spatiotemporal evolution mechanism of total phosphorus (TP) in groundwater to solve the diffusion regular pattern of TP in PGB bodies, as well as to manage and mitigate the impacts of TP on the groundwater system. In this study, leaching toxicity experiments and a numerical groundwater simulation software (GMS10.4) were combined to develop a three-dimensional conceptual model for predicting the groundwater flow and contaminant transport under steady-state conditions in a phosphorus mine in Anhui. The results showed a lower TP concentration than the TP standard concentration (0.2 mg/L) at a source concentration of 0.59 mg/L. However, groundwater TP source concentrations of 1.88 and 2.46 mg/L in the study area were found to exceed the standard concentration for a certain time and areas. In addition, the transport and dispersion of TP are influenced not only by the groundwater flow field, drainage ditches, rivers, and wells but also by the adsorption and attenuation effects of the soil that occur during the transport process, affecting the dispersion distance and distribution of groundwater TP concentrations. The results of the present study can promote the development of groundwater-friendly PGB technology, providing a great significance to the construction of green mines and the promotion of ecological civilization. Full article

The unique climate conditions and water source composition in the Tianshan Mountain provide a good experimental site for verifying the relationships between water resources and climate change on a larger scale. With the help of water isotopes (D, ¹⁸O), a more reliable conceptual model of groundwater systems can be constructed on both local and regional scales, especially in areas that are susceptible to climate change and under pressure from intensive human activities. In this paper, we present δ¹⁸O, δD, d-excess, RWLs and altitude effects of river water and groundwater based on the data derived from our network of stable isotope sampling sites along the Kaidu River. Stable isotope mass balance was applied to study the interactions between groundwater and surface water and to quantify the recharge proportions between bodies of water in typical regions. The results showed that the Kaidu River is composed of precipitation, ice and snow melt, baseflow and groundwater. The percentage of groundwater increased with the distance between upstream (the runoff producing area) and the leading edge of the glacier. The two recharge areas are the spring overflow from the mountain area to the alluvial layer of the inclined plain and the leading edge of the alluvial plains to areas with fine soil. The groundwater recharge ratio is about 23% in high mountain areas but 46% or more in the middle and lower reaches. These results generated a more comprehensive understanding of the hydrological cycle of inland rivers in arid regions. Full article

Groundwater is a major source of drinking water worldwide, often considered more reliable than surface water and more accessible. Nowadays, there is wide recognition by the scientific community that groundwater resources are under threat from overexploitation and pollution. Furthermore, frequent and prolonged drought periods due to climate change can seriously affect groundwater recharge. For an appropriate and sustainable management of water systems supplied by springs and/or groundwater withdrawn from aquifers through drilling wells or drainage galleries, the need arises to properly quantify groundwater resources availability, mainly at the monthly scale, as groundwater recharge is influenced by seasonality, especially in the Mediterranean areas. Such evaluation is particularly important for ungauged groundwater bodies. This is the case of the aquifer supplying the Santissima Aqueduct, the oldest water supply infrastructure of the city of Messina in Sicily (Southern Italy), whose groundwater flows are measured only occasionally through spring water sampling at the water abstraction plants. Moreover, these plants are barely maintained because they are difficult to reach. In this study, groundwater recharge assessment for the Santissima Aqueduct is carried out through a GIS-based inverse hydrogeological balance methodology. Although this approach was originally designed to assess aquifer recharge at the annual scale, wherever a model conceptualization of the groundwater system was hindered by the lack of data, in the present study some changes are proposed to adjust the model to the monthly scale. In particular, the procedure for evapotranspiration assessment is based on the Global Aridity Index within the Budyko framework. The application of the proposed methodology shows satisfactory results, suggesting that it can be successfully applied for groundwater resources estimation in a context where monthly information is relevant for water resources planning and management. Full article

The hydrogeochemical characteristics of the significant subterranean water body between “Cecina River and San Vincenzo” (Italy) was evaluated using multivariate statistical analysis methods, like principal component analysis and self-organizing maps (SOMs), with the objective to study the spatiotemporal relationships of the aquifer. The dataset used consisted of the chemical composition of groundwater samples collected between 2010 and 2018 at 16 wells distributed across the whole aquifer. For these wells, all major ions were determined. A self-organizing map of 4 × 8 was constructed to evaluate spatiotemporal changes in the water body. After SOM clustering, we obtained three clusters that successfully grouped all data with similar chemical characteristics. These clusters can be viewed to reflect the presence of three water types: (i) Cluster 1: low salinity/mixed waters; (ii) Cluster 2: high salinity waters; and (iii) Cluster 3: low salinity/fresh waters. Results showed that the major ions had the greater influence over the groundwater chemistry, and the difference in their concentrations allowed the definition of three clusters among the obtained SOM. Temporal changes in cluster assignment were only observed in two wells, located in areas more susceptible to changes in the water table levels, and therefore, hydrodynamic conditions. The result of the SOM clustering was also displayed using the classical hydrochemical approach of the Piper plot. It was observed that these changes were not as easily identified when the raw data were used. The spatial display of the clustering results, allowed the evaluation in a hydrogeological context in a quick and cost-effective way. Thus, our approach can be used to quickly analyze large datasets, suggest recharge areas, and recognize spatiotemporal patterns. Full article

This paper conceptualizes and evaluates the groundwater resource in a coastal urban area hydrologically influenced by peri-urban irrigation agriculture. Adra town in southern Spain was the case study chosen to evaluate the groundwater resource contributed from the northern steep urban sector (NSUS) to the southern flat urban sector (SFUS), which belongs to the Adra River Delta Groundwater Body (ARDGB). The methodology included (1) geological and hydrogeological data compilation; (2) thirteen Multichannel Analysis of Surface Waves (MASW), and eight Ground Penetrating Radar (GPR) profiles to define shallow geological structures and some hydrogeological features; (3) hydrogeological surveys for aquifer hydraulic definition; (4) conceptualization of the hydrogeological functioning; and (5) the NSUS groundwater resource evaluation. All findings were integrated to prepare a 1:5000 scale hydrogeological map and cross-sections. Ten hydrogeological formations were defined, four of them (Paleozoic weathered bedrock, Pleistocene littoral facies, Holocene colluvial, and anthropogenic filling) in the NSUS contributing to the SFUS. The NSUS groundwater discharge and recharge are, respectively, around 0.28 Mm³ year⁻¹ and 0.31 Mm³ year⁻¹, and the actual groundwater storage is around 0.47 Mm³. The groundwater renewability is high enough to guarantee a durable small exploitation for specific current and future urban water uses which can alleviate the pressure on the ARDGB. Full article

A multi-component geochemical dataset was collected from groundwater and surface-water bodies associated with the urban Fountain Creek alluvial aquifer, Colorado, USA, to facilitate analysis of recharge sources, geochemical interactions, and groundwater-residence times. Results indicate that groundwater can be separated into three distinct geochemical zones based on location within the flow system and proximity to surface water, and these zones can be used to infer sources of recharge and groundwater movement through the aquifer. Rare-earth-element concentrations and detections of wastewater-indicator compounds indicate the presence of effluent from wastewater-treatment plants in both groundwater and surface water. Effluent presence in groundwater indicates that streams in the area lose to groundwater in some seasons and are a source of focused groundwater recharge. Distributions of pharmaceuticals and wastewater-indicator compounds also inform an understanding of groundwater–surface-water interactions. Noble-gas isotopes corroborate rare-earth-element data in indicating geochemical evolution within the aquifer from recharge area to discharge area and qualitatively indicate variable groundwater-residence times and mixing with pre-modern groundwater. Quantitative groundwater-residence times calculated from ³H/³He, SF₆, and lumped-parameter modeling generally are less than 20 years, but the presence of mixing with older groundwater of an unknown age is also indicated at selected locations. Future investigations would benefit by including groundwater-age tracers suited to quantification of mixing for both young (years to decades) and old (centuries and millennia) groundwater. This multi-faceted analysis facilitated development of a conceptual model for the investigated groundwater-flow system and illustrates the application of an encompassing suite of analytes in exploring hydrologic and geochemical interactions in complex systems. Full article

Inorganic compounds in groundwater may derive from both natural processes and anthropogenic activities. The assessment of natural background levels (NBLs) is often useful to distinguish these sources. The approaches for the NBLs assessment can be classified as geochemical (e.g., the well-known pre-selection method) or statistical, the latter involving the application of statistical procedures to separate natural and anthropogenic populations. National Guidelines for the NBLs assessment in groundwater have been published in Italy (ISPRA 155/2017), based mainly on the pre-selection method. The Guidelines propose different assessment paths according to the sample size in spatial/temporal dimension and the type of the distribution of the pre-selected dataset, taking also into account the redox conditions of the groundwater body. The obtained NBLs are labelled with a different confidence level in function of number of total observations/monitoring sites, extension of groundwater body and aquifer type (confined or unconfined). To support the implementation of the Guidelines, the on-line tool evaluation of natural background levels (eNaBLe), written in PHP and using MySQL as DBMS (DataBase Management System), has been developed. The main goal of this paper is to describe the functioning of eNaBLe and test the tool on a case study in central Italy. We calculated the NBLs of As, F, Fe and Mn in the southern portion of the Mounts Vulsini groundwater body, within the volcanic province of Latium (Central Italy), also separating the reducing and oxidizing facies. Specific results aside, this study allowed to verify the functioning and possible improvements of the online tool and to identify some criticalities in the procedure NBLs assessment at the groundwater body scale Full article

Understanding the connectivity between surface water and groundwater is key to sound geo-hazard prevention and mitigation in a waterscape such as the Jiuzhaigou Natural World Heritage Site in the southeast Tibetan Plateau, China. In this study, we used environmental isotope tracers (²H, ¹⁸O ³H, and ²²²Rn) to constrain a water cycle model including confirming hydrological pathways, connectivity, and water source identification in the Jiuzhaigou catchments. We established the local meteoric water line (LMWL) based on the weekly precipitation isotope sampling of a precipitation station. We systematically collected water samples from various water bodies in the study area to design the local water cycle model. The regional water level and discharge changes at one month after the earthquake indicated that there was a hydraulic connection underground across the local water divide between the Rize (RZ) river in the west and Zechawa (ZCW) lake in the east by the δ¹⁸O and δ²H measurements. We employed an end-member mixing model to identify and quantify Jiuzhaigou runoff-generating sources and their contributions, and we found that the average contributions of precipitation and groundwater to the surface runoff in the catchments are about 30% and 70%, respectively. The two branches of the Shuzheng (SZ) trunk were recharged by 62 ± 19% from the ZCW lake and 38 ± 19% from the RZ river, which was consistent with the fractions calculated by the actual discharge volume. ²²²Rn mass balance analyses were employed to estimate the water exchange between groundwater and river, which further confirmed this estimate. ²²²Rn concentrations and ³H contents showed that the groundwater had a short residence time and it was moderate precipitation, thought the contribution of groundwater to the river was 70%, according to the different tracers. A three-dimensional conceptual model of the water cycle that integrated the regional hydrological and geological conditions was established for the catchments. Full article

Nitrate pollution in groundwater and its mitigation strategies is currently a topic of controversial debate in Germany, and the demand for harmonised approaches for the implementation of regulations is increasing. Important factors that need to be considered when planning mitigation measures are the nitrogen inputs into water bodies and the natural nitrate reduction capacity. The present study introduces a nationwide, harmonised and simplified approach for estimating nitrate reduction as an integral quantity across the unsaturated zone and the groundwater body. The nitrate reduction rates vary from 0% to 100%, and are on average 57%, with high values in the north of Germany and low values in the south. Hydrogeological characteristics are associated with the estimated nitrate reduction rates, whereby the influence of aquifer type and redox conditions are particularly relevant. The nitrate reduction rates are substantially higher in porous aquifers and under anaerobic conditions than in fractured, consolidated aquifers and under aerobic conditions. This contribution presents a harmonised conceptual approach to derive the nitrate reduction rate at a 1 km × 1 km resolution. This information can be used when planning and designing mitigation measures to meet the groundwater nitrate limits. Full article

Springs are crucial interfaces within the Earth’s Critical Zone, connecting water and its related matter and energy at different scales from the microscopic to the macroscopic level. This connectivity is of importance for habitat conditions and the invertebrate community in springs as ecotones at the groundwater–surface water and the aquatic–terrestrial interfaces in headwater regions. Here, an integrative approach regarding an appropriate theoretical framework is given as an opinion on coupling perspectives from Ecohydrology and Earth Science. A theoretical integration within the approaches of the concepts of Earth’s Critical Zone and Hydropedology with its hierarchical framework is considered for bridging multiple scales from the individual substrate type to the entire spring habitat and the headwater catchment. The paper is in every respect an opinion on theoretical approaches and provides a synthesis within a conceptual framework for spring habitats, which should give further insight into how to study such small water bodies in the context of its adjacent landscape settings. Full article