Search Results (1,170)

To address the problems of salinization of the soil in gully control and land-making projects, the formation mechanism of soil interflow from a gully valley on the Loess Plateau was investigated, regarding its interface, water source, and spatial-temporal distribution characteristics, through field location monitoring and isotope tracer technique. The results showed the following: (1) there are two types of soil interflow in the Loess Plateau, namely soil interflow in slope and in gully, with interflow in gully being the main form; (2) adequate water supply, layered soil structure, and geographic disparity are conditions for the formation of soil interflow in the gully; (3) soil water is recharged by precipitation, surface water, and groundwater. Surface water is an important source of soil water recharge at the 0–100 cm depth, whereas groundwater is an important source of soil water recharge at the 100–200 cm depth. The results provide a basis for the regulation of the soil interflow, resource utilization, and land quality improvement in the Loess Plateau. Full article

Change in land use and land cover (LULC) is crucial to freshwater ecosystems as it affects surface runoff, groundwater storage, and sediment and nutrient transport within watershed areas. Ecosystem components such as wetlands, which can contribute to the reduction of water pollution and the enhancement of groundwater recharge, are altered by LULC modifications. This study evaluates how wetlands in the Big Sunflower River Watershed (BSRW) have changed in recent years and quantified their impacts on streamflow, water quality, and groundwater storage using the Soil and Water Assessment Tool (SWAT). The model was well calibrated and validated prior to its application. Our study showed that the maximum increase in wetland areas within the sub-watersheds of interest was 26% from 2008 to 2020. The maximum changes in reduction due to the increase in wetland areas were determined by 2% for streamflow, 37% for total suspended solids, 13% for total phosphorus (TP), 4% for total nitrogen (TN), and the maximum increase in shallow groundwater storage by 90 mm from 2008 to 2020 only in the selected sub-basins. However, the central part of the watershed experienced average declines of groundwater levels up to 176 mm per year due to water withdrawal for irrigation or other uses. This study also found that restoration of 460 to 550 ha of wetlands could increase the reduction of discharge by 20%, sediment by 25%, TN by 18%, and TP by 12%. This study highlights the importance of wetland conservation for water quality improvement and management of groundwater resources. Full article

Jiamusi is situated in Heilongjiang Province, China, in the center of the Sanjiang Plain. The 1980s’ overplanting of paddy fields resulted in a decrease in groundwater levels, scarcity of groundwater resources, and frequent earth collapses. Examining and safeguarding the groundwater resources in this region has emerged as a crucial subject. In light of this, this paper uses the remote sensing water balance method and the SWAT distributed hydrological model to calculate groundwater resources in the Jiamusi area. It also conducts scientific experiments by examining various factors, including rainfall, the degree of water supply, soil type, and land use. The measured monthly runoff of Jiamusi City’s Tongjiang and Fuyuan City’s hydrology stations was utilized to establish the model parameters for the SWAT model. A preliminary assessment of the distribution features of shallow groundwater in the Jiamusi area is conducted using the two methodologies mentioned above, and the following results are reached: (1) Tongjiang Hydrological Station and Fuyuan Hydrological Station both had good runoff modeling results, with R² and NS values of 0.81, 0.77, and 0.77, 0.75, respectively. (2) The SWAT model works well for assessing groundwater resources. Between 2010 and 2016 (two preheating years), Jiamusi’s average groundwater recharge was 61.03 × 10⁸ m³, with a recoverable amount of 27.4 × 10⁸ m³. (3) Based on the remote sensing water balancing approach, the average exploitable quantity of groundwater recharge in the Jiamusi area between 2008 and 2016 is 23.94 × 10⁸ m³, while the average recharge in the area is 53.2 × 10⁸ m³. (4) The Jiamusi metropolitan area is the core of the groundwater phreatic reservoir water reserves, which progressively decline in both the northeast and southeast directions. It falls to the southwest as Fuyuan City’s center. The Songhua River’s main stream area near Tongjiang City has the least volume of water reserves in the phreatic layer, and the area’s groundwater reserves converge to the southeast and northwest, where surface water makes up the majority of the water resources. Full article

Stable isotope abundances (δ¹⁸O and δ²H) in regional aquifers can provide important paleoclimate information. However, identifying paleoclimate signals can be complicated by cross-formational mixing and, potentially, by isotopic diffusion between aquifers and confining units. We examine controls on δ¹⁸O and δ²H distributions in the Wilcox aquifer of the northern Gulf Coastal Plain (USA). We sampled groundwater for δ¹⁸O, δ²H, Cl⁻, and ³⁶Cl along a ~300 km downgradient transect. We developed a simplified, 1D numerical model of groundwater flow and ¹⁸O transport to assess the possible importance of isotopic diffusion between the aquifer and its confining units. Along the inferred flowpath, δ¹⁸O and δ²H values were depleted by as much as 1.3 and 8.2‰, respectively, as the Wilcox aquifer transitioned from unconfined to confined. However, they then gradually rose farther downgradient by up to 1.1 and 8.6‰. Chlorine-36 analyses and ¹⁴C analyses (from other studies) indicate that groundwater ages range from ~10³ yr to ~8 × 10⁵ yr. Modeling results indicate that the effect of diffusion on isotopic abundances is limited, whereas Cl⁻ data indicate that cross-formational flow is limited. Therefore, we posit that confined groundwater in our study reflects a Pleistocene paleorecharge signal. Full article

To keep groundwater levels stable, Jinan’s government has implemented several water management measures. However, considerable volumes of dissolved organic carbon (DOC) can enter groundwater via water exchange, impacting groundwater stability. In this study, a SWAT-MODFLOW-RT3D model designed specifically for the Yufu River Basin is developed, and part of the code of the RT3D module is modified to simulate changes in DOC concentrations in groundwater under different artificial recharge scenarios. The ultimate objective is to offer valuable insights into the effective management of water resources in the designated study region. The modified SWAT-MODFLOW-RT3D model simulates the variations of DOC concentration in groundwater under three artificial recharge scenarios, which are (a) recharged by Yellow River water; (b) recharged by Yangtze River water; and (c) recharged by Yangtze River and Yellow River water. The study shows that the main source of groundwater DOC in the basin is exogenous water. The distribution of DOC concentration in groundwater in the basin shows obvious spatial variations due to the influence of infiltration of surface water. The area near the upstream riverbank is the earliest to be affected. With the prolongation of the artificial recharge period, the DOC concentration in groundwater gradually rises from upstream to downstream, and from both sides of the riverbank to the surrounding area. By 2030, the maximum level of DOC in the basin will exceed 6.20 mg/l. The Yellow River water recharge scenario provides more groundwater recharge and less DOC input than the other two scenarios. The findings of this study indicate that particularly when recharge water supplies are enhanced with organic carbon, DOC concentrations in groundwater may alter dramatically during artificial recharge. This coupled modeling analysis is critical for assessing the impact of recharge water on groundwater quality to guide subsequent recharge programs. Full article

This study aims to investigate the intricate relationship between geological structures, water chemistry, and isotopic composition in order to gain a deeper understanding of the origins and recharge mechanisms of thermal–mineral waters in the Kyllini region. The research integrates tectonic analysis, hydrochemical data, and stable isotope measurements to delineate recharge zones and trace the origin of these unique water sources. The methods used for delineation are the geological and tectonic study of the area, as well as hydrochemical and isotopic data analysis. The findings highlight that tectonic activity creates preferential flow paths and consequently influences the hydrogeological framework, facilitating deep circulation and the upwelling of thermal waters. Monthly analyses of groundwater samples from the Kyllini thermal spring were conducted over one hydrological year (2019–2020) and compared with data from the area collected in 2009. The hydrochemical profiles of major and minor ions reveal distinct signatures corresponding to various water–rock interactions, while stable isotope analysis provides insights into the climatic conditions and altitudes of recharge areas. Hydrochemical analyses reveal the composition of thermal–mineral waters, aiding in the identification of potential sources and their evolution. The conceptualization of Kyllini contributes to the deeper understanding of the intricate interplay between tectonics, hydrochemistry, and stable isotopes. During a hydrological year, the water type of Kyllini’s spring groundwater remains the same (Na-Cl-HCO₃), presenting only slight alterations. Full article

Jinan, renowned as the “Spring City” in China, relies significantly on karst groundwater as an indispensable resource for socio-economic development, playing a crucial role in ecological regulation, tourism, and historical and cultural aspects. The Yufu River basin, situated within Jinan’s karst region, represents a vital riverine leakage zone. Therefore, investigating the evolutionary characteristics and causative mechanisms of surface water and groundwater at different aquifer levels in the Yufu River basin can provide a scientific foundation for the protection of Jinan’s springs. This study, based on hydrogeochemical and isotopic data from the river water, shallow groundwater, deep groundwater, and springs in the Yufu River basin, explored the hydrogeochemical evolution in this region. The findings revealed significant spatial variations in the hydrochemical parameters of the Yufu River basin. Groundwater received contributions from surface water, while springs represented a mixture from both surface water and various recharge aquifers. Dominant ions include Ca²⁺ and HCO₃⁻, with prevailing hydrochemical types being HCO₃·SO₄-Ca and HCO₃-Ca. Atmospheric precipitation served as the primary source of recharge for surface water and groundwater in the Yufu River basin, albeit influenced by pronounced evaporation processes. The hydrochemical composition in the Yufu River basin was primarily attributed to water–rock interactions, mainly driven by the combined effects of carbonate rock, silicate rock, and gypsum weathering and dissolution. Among these, the weathering and dissolution of carbonate rocks played a dominant role, with human activities exerting a relatively minor influence on the hydrochemistry of the Yufu River basin. Full article

For insight into the productive and storage mechanisms of biogas in the Qaidam Basin, efforts were made to investigate the groundwater recharge and the processes of hydrocarbon generation by CDOM-EEM (fluorescence excitation-emission matrix of Chromophoric dissolved organic matter) spectrum, hydrogen and oxygen isotopes, and geochemical characters in the central depression of the Qaidam Basin, China. The samples contain formation water from three gas fields (TN, SB, and YH) and surrounding surface water (fresh river and brine lake). The results indicate that modern precipitation significantly controls the salinity distribution and organic matter leaching in the groundwater system of the central depression of the Qaidam Basin. Higher salinity levels inhibit microbial activity, which leads to organic matter degradation and to gas generation efficiency being limited in the groundwater. The inhabitation effect is demonstrated by the notable negative correlation between the extent of organic matter degradation and its concentration with hydrogen and oxygen isotopes. The conclusion of this study indicated that modern precipitation emerges as a crucial factor affecting the biogas production and storage in the Qaidam Basin by influencing the ultimate salinity and organic matter concentration in the formation, which provides theoretical insight for the maintenance of modern gas production wells and the assessment of gas production potential. Full article

Groundwater is a vital resource in the Chuoshui River alluvial plain (CSAP), a key agricultural area in Taiwan. Understanding groundwater recharge is crucial for sustainable water management amidst changing climatic conditions and increasing water demand. This study investigates the major ion composition, solute Sr concentrations, and ⁸⁷Sr/⁸⁶Sr ratios in groundwater and stream water from the Choushui River (CSR) to trace groundwater recharge sources. The Piper diagram reveals that most groundwater samples are of the freshwater Ca–HCO₃ type, aligning with the total dissolved solids (TDS) classification. TDS and major ion compositions indicate that groundwater near Baguashan Terrace (BGT) and Douliu Hill (DLH) primarily derives from stream water and rainwater. Na⁺ and Cl⁻ enrichment in some aquifers of BGT and DLH is attributed to the dissolution of paleo-sea salt and mixing with paleo-seawater from sedimentary porewater. Elevated dissolved Sr concentrations and lower ⁸⁷Sr/⁸⁶Sr ratios in these aquifers further support the intrusion of paleo-seawater. Groundwater in the proximal fan shows high TDS due to intensive weathering, complicating the use of TDS as a tracer. Sr isotopic compositions and solute Sr²⁺ concentrations effectively distinguish recharge sources, revealing that the CSR mainstream primarily recharges the proximal fan and BGT region, while CSR tributaries and rainwater mainly recharge the DLH region. This study concludes that Sr isotopic compositions and solute Sr²⁺ concentrations are more reliable than TDS and major ion compositions in identifying groundwater recharge sources, enhancing our understanding of groundwater origins and the processes affecting water quality. Full article

Understanding the historical groundwater recharge process and its influencing factors is crucial for effectively managing regional groundwater resources amidst future climate change. However, the availability of high-resolution hydroclimate archives remains severely limited. In this study, we used a 59 m chloride profile within the unsaturated loess zone to reconstruct the potential groundwater recharge (PGR) records spanning 273 years in a near-humid area on the Loess Plateau. Spectral analysis was employed to identify the principal influencing factors on PGR across various time scales. The reconstructed hydrological records revealed three wet periods and four dry periods from 1745 to 2007 AD, with PGR rates ranging from 66.7 to 222.4 mm yr⁻¹ during wet periods and 20.0 to 66.7 mm yr⁻¹ during dry periods. In addition, spectral analysis indicated multiple cycles, ranging from 2.1 to 50.0 years, within the PGR history. Temperature, precipitation, and sunspot activity emerged as the key factors governing the rate of PGR over the 3-year, 7-year, and 11-year time scales, respectively, highlighting the combined influence of solar activity and climate on the PGR process. These findings enhance our understanding of groundwater recharge and environmental climate dynamics in the near-humid loess unsaturated zone and other regions exhibiting similar hydroclimatic conditions. Full article

This paper discusses the groundwater vulnerability to pollution assessment for the Tirana–Ishmi alluvium aquifer, Albania. Economic activities, municipal wastewater discharged into rivers and groundwater overexploitation threaten to pollute the groundwater. Based on the aquifer characteristics and the available data, SINTACS was selected as the most realistic assessment model. The SINTACS parameters’ rates assigned to the aquifer’s characteristics (water table depth, infiltration, unsaturated zone, soil media, aquifer media, hydraulic conductivity, topography) were adapted to the local features, followed by GIS vulnerability mapping. Statistical analysis indicates that the unsaturated zone, hydraulic conductivity and aquifer media have the highest influence on groundwater vulnerability, whereas topography has the lowest influence. Validation through sensitivity analysis and nitrates content confirms the rational selection of the SINTACS model and the reliability of the study’s outputs. The most vulnerable areas to pollution are the recharge zones, followed by the highly urbanized Tirana City area, characterized by high levels of groundwater extraction rate and wastewater discharged into the rivers. The paper, being the first completed groundwater vulnerability assessment of the study area, could serve as a basis for a scientific–based groundwater management that should be considered in local territory planning. Full article

This study investigates the Batha endorheic basin in Chad, situated east of the Lake Chad basin in the arid to semi-arid Sahelian zone. This region has not yet undergone comprehensive geological and hydrogeological studies. More broadly, the transition zone between semi-arid and arid climates has been minimally explored. This research aims to evaluate the resources and dynamics of this multi-layered system using a combined geology-hydrogeology-hydrochemistry-isotopes approach. The multilayer system includes sedimentary layers (Quaternary, Pliocene, and Eocene) over a crystalline basement. A piezometric investigation of the system shows a general SE–NW groundwater, indicating an interconnection between all layers. Hydrochemical analyses identifies four main facies (calcium-bicarbonate, sodium-bicarbonate, sulphate-sodium, and mixed), primarily controlled by water–rock interaction with secondary influences from base-exchange and evaporation. Saturation indices indicate that these waters are close to equilibrium with the calcite-Mg phases, gaylussite and gypsum. Stable isotopes (oxygen-18 and deuterium) categorize groundwater into three groups: ancient water, recent and older meteoric water mixtures affected by evaporation, and mixtures more heavily impacted by evaporation. Tritium contents reveal three groups: current rainwater, modern water, and sub-modern water. These results indicate that ionic and isotopic differentiations cannot be strictly linked to specific layers, confirming the interconnected nature of the Batha system. The observed heterogeneity is mainly influenced by lithological and climatic variations. This study, though still limited, enhances significantly the understanding of the basin’s functioning and supports the rational exploitation of its vital resources for the Batha area’s development. Future investigations to complete the present study are highlighted. Full article

Understanding the recharge–discharge system of a catchment is key to the efficient use and effective management of groundwater resources. The present study focused on the estimation of groundwater recharge using Soil Moisture Balance (SMB) and Baseflow Separation (BFS) methods in the Gilgel Gibe catchment where water demand for irrigation, domestic, and industrial purposes is dramatically increasing. The demand for groundwater and the existing ambitious plans to respond to this demand will put a strain on the groundwater resource in the catchment unless prompt intervention is undertaken to ensure its sustainability. Ground-based hydrometeorological 36-years data (1985 to 2020) from 17 stations and satellite products from CHIRPS and NASA/POWER were used for the SMB method. Six BFS methods were applied through the Web-based Hydrograph Analysis Tool (WHAT), SepHydro, BFLOW, and Automated Computer Programming (PART) to sub-catchments and the main catchment to estimate the groundwater recharge. The streamflow data (discharge) obtained from the Ministry of Water and Energy were the main input data for the BFS methods. The average annual recharge of groundwater was estimated to be 313 mm using SMB for the years 1985 to 2020 and 314 mm using BFS for the years 1986 to 2003. The results from the SMB method revealed geographical heterogeneity in annual groundwater recharge, varying from 209 to 442 mm. Significant spatial variation is also observed in the estimated annual groundwater recharge using the BFS methods, which varies from 181 to 411 mm for sub-catchments. Hydrogeological conditions of the catchment were observed, and the yielding capacity of existing wells was assessed to evaluate the validity of the results. The recharge values estimated using SMB and BFS methods are comparable and hydrologically reasonable. The findings remarkably provide insightful information for decision-makers to develop effective groundwater management strategies and to prioritize the sub-catchments for immediate intervention to ensure the sustainability of groundwater. Full article

Water Sowing and Harvesting (WS&H) is an ancestral knowledge widely used as a sustainable technique in water management. This study aims to analyse the importance, promotion, and cultural heritage of WS&H techniques through a literature review in Ecuador, considering applications of ancestral techniques by region (coastal, Andean and insular) with a strengths, opportunities, weaknesses, and threats (SWOTs) analysis and a focus group for a strategy proposal of the water supply. The methodology of this study includes the following: (i) an analysis of the evolution of WS&H studies in Ecuador; (ii) a presentation of WS&H techniques and their applications; and (iii) the contribution of WS&H to the Sustainable Development Goals (SDGs), complemented by a SWOTs analysis. The results show that, in Ecuador, WS&H is a method of Nature-based Solutions (NbSs) applied to the problems of water scarcity and is affordable, ecological, and has high efficiency, improving agricultural productivity and guaranteeing water supply for human consumption. The Manglaralto coastal aquifer, a case study in the coastal region of Ecuador, involves WS&H management and artificial aquifer recharge. WS&H structures became a reference for the sustainable development of rural communities that can be replicated nationally and internationally as a resilient alternative to water scarcity and a global climate emergency, contributing to the SDGs of UNESCO. Full article

This study investigates the processes leading to karst development in the southeastern part of Riyadh city extending up to Al Kharj. Numerous solution features such as sinkholes, collapsed dolines, and solution caverns are common in the area. The role of water in the development of the karst features was investigated using an integrated geological and hydrochemical approach. Geological investigations included the petrographic analysis of rock samples collected from zones of intense karstification with special emphasis on mineral dissolution. The study showed that the Sulaiy Formation is commonly fractured, brecciated, foliated, and contains numerous cavities, vugs, and openings. These features have formed by mineral dissolution by circulating groundwater, which has removed anhydrite beds from the underlying Arab–Hith sequence. Karstification likely started from the tectonically weak zones when there was more groundwater recharge. Studies show that during the early to mid-Holocene period, the climate in the Arabian Peninsula was humid, promoting groundwater recharge and subsequent mineral dissolution, though the process of karstification must have started much earlier. Hydrochemical findings reveal that mineral dissolution (halite and calcium sulfate) is the main process affecting groundwater chemistry. The Piper plot revealed two main hydrochemical facies: the (Ca²⁺ + Mg²⁺)–(Cl+ SO₄²⁻) Type (Type A) and the (Na⁺ + K⁺)–(SO₄²⁻ + Cl) Type (Type B). Most of the samples belong to Type B, typical of groundwater facies affected by dissolution of halite and anhydrite mineral. The absence of the (Ca²⁺ + Mg²⁺)–(CO₃²⁻ + HCO₃⁻) type of groundwater facies indicates a lack of recent groundwater recharge and the removal of carbonate minerals from the system through precipitation, as evidenced by the saturation indices. Plots of the major ionic pairs (cations vs. anions) in groundwater indicate strong halite and gypsum/anhydrite dissolution. Of the three carbonate minerals, calcite has the highest average saturation index followed by aragonite and dolomite. This suggests significant past rock–water interaction leading to carbonate dissolution. Presently, any additional calcium or carbonate ions introduced into the water lead to calcite precipitation. The study indicates that the process of karst development may not be active today. Currently, groundwater chemistry is mainly influenced by rock–water interaction leading to gypsum/anhydrite dissolution, which has resulted in a high concentration of Na⁺, Ca²⁺, Cl⁻ and SO₄²⁻ ions in groundwater. The dissolution of gypsum and halite from the Hith Formation weakens the structural integrity of the overlying Sulaiy Formation, creating large underground cavities. These cavities increase the risk of roof collapse, leading to cover-collapse sinkholes as the roof becomes too thin to support the weight above. Full article