Search Results (205)

Geothermal energy is a locally available, low-carbon resource that may support heat supply, building decarbonisation and regional energy diversification in non-volcanic crystalline settings. This study proposes an exploratory GIS-based approach for geothermal favourability mapping in the Guarda District, Central Portugal, where Hercynian granites, major fault systems and thermal and mineral water occurrences define a structurally controlled hydrogeothermal framework. Hydrogeochemical data from 54 groundwater abstraction points were integrated through silica-derived apparent geothermometric indicators, classical hydrothermal-parameter estimation and Empirical Bayesian Kriging Regression Prediction (EBKRP). Apparent silica-derived temperature indicators, circulation depth, geothermal gradient and theoretical thermal power were estimated, with log₁₀ transformed thermal power used as the dependent variable and distance to major mapped faults as the structural covariate. Apparent silica-derived temperature indicators range from 21.3 °C to 121.2 °C, with a mean of 64.6 °C, while estimated geothermal gradients range from 20.3 °C/km to 92.1 °C/km. Higher estimated values occur preferentially near NE–SW and NNW–SSE fault systems, suggesting that structural permeability may influence deep groundwater circulation. The interpretation explicitly acknowledges that, in low-temperature systems, dissolved silica may be influenced by chalcedony or amorphous silica control, as well as by cooling, mixing and incomplete re-equilibration during fluid ascent. The resulting map is interpreted as a screening-level favourability product, not as a definitive assessment of exploitable geothermal resources, and supports the prioritisation of future structural mapping, geophysical surveys, exploratory drilling, borehole temperature logging and applied geothermal assessment in fractured granitic terrains. Full article

Analytical solutions for contaminant transport in porous media are important for understanding subsurface processes and validating numerical models. However, conventional Laplace-transform-based approaches often face difficulties in handling realistic transient boundary conditions and typically result in challenging inverse formulations that require computationally intensive convolved integration. To address these limitations, this paper presents a Fourier-FFT analytical framework for solving the well-established one-dimensional advection–dispersion–reaction (ADR) equation in homogeneous and heterogeneous porous domains. The proposed Fourier-FFT approach enables straightforward mathematical formulation, rapid computation, and incorporation of realistic transient boundary conditions beyond idealized step or impulse inputs. Verification against a Laplace-based analytical solution for a homogeneous domain and a finite element solution for a dual-permeability domain show good agreement, confirming the accuracy of the method. Parametric analyses further demonstrate that the framework captures the expected physical behaviour of contaminant transport under varying hydrogeological and reaction conditions. Full article

The transport and distribution of Scomber japonicus larvae significantly affect their habitat and population dynamics. Understanding these processes is crucial for developing effective fishing and conservation strategies. However, the interannual variability of the Kuroshio path introduces both complexity and uncertainty. This study implemented a coupled ocean–biophysical model to simulate and analyze the transport of S. japonicus larvae in the Pacific Ocean south of Japan across three Kuroshio path modes, including the offshore non-large-meander (ONLM), nearshore non-large-meander (NNLM), and typical large-meander (TLM) paths. Two transport scenarios, passive drift (PD) and active swimming (AS), were considered in the simulations. The simulated results presented a comprehensive analysis of the distribution, connectivity, and transport distances of S. japonicus larvae. These findings highlighted the significant influence of biological behavior on larval transport, notably reducing transport distances and shifting the distributions northward. This allowed larvae to actively migrate to areas with higher zooplankton aggregation. Larvae released from the western and nearshore spawning grounds around Southern Kyushu–Shikoku were mainly transported to the central nursery region between 132.5° E and 140° E, whereas larvae released from the eastern spawning grounds were mainly distributed in the eastern nursery region east of 140° E near the Kuroshio Extension. These patterns suggest that nursery areas 2 and 3 may warrant further attention in future spatial management assessments, particularly when considering larval transport under different Kuroshio path modes. This study provides valuable insights into the transport and distribution mechanisms of S. japonicus larvae, offering critical guidance for the conservation of fishery resources and the promotion of sustainable fishery management. Full article

A wave-resource characterization along the coast of Vietnam was performed based on the 12-year period from 2007 to 2018, using the structured-grid Simulating WAves Nearshore (SWAN) model with a ~2.3 km spatial resolution. Extensive model validations were performed using an observed nearshore dataset and ERA5 offshore datasets. The wave parameters, significant wave height, wave period, total wave energy and omnidirectional wave power varied both spatially and temporally, with a strong seasonal pattern influenced by the northeast and southwest monsoons, with the impact of the northeast monsoon being stronger. Wave energy resources were highest in winter and lowest in summer, making the southcentral coast of Vietnam a prime location for wave energy harvesting. However, further feasibility and design studies are needed before wave farms can be established. The Gulf of Tonkin and the Gulf of Thailand had lower wave energy due to wind distribution, shadowing effects and changes in water depth. This study also noted the impact of ENSO phases on wave conditions. Year-round, El Niño generally weakened winds, leading to smaller waves and reduced wave energy, while La Niña had the opposite effect. Additionally, tropical cyclones can further amplify significant wave height, especially during both ENSO phases in July, thereby increasing wave energy. Full article

Water levels in the Great Salt Lake (GSL), UT, USA, have been declining overall since 1989, leading to a 70% decrease in surface area. To understand GSL’s future, we seek to image fresh groundwater input and lithologic variation along the lake’s boundary. Determining the amount of groundwater recharge into GSL is crucial for lake management but currently unknown. During the Fall of 2024 and Spring 2025, we conducted 16 electrical resistivity tomography (ERT) and six transient electromagnetic (TEM) surveys along the southern shore of GSL between Burmester Road (to the West), Saltair, and Lee’s Creek (to the East). These measurements indicate a low-resistivity layer consistent with brine pore-water, with variable thickness ranging from 7.1 ± 0.1 m at Burmester to 9.6 ± 0.2 m at Saltair. The Saltair region shows a high-resistivity layer, consistent with a 4.4 ± 0.05 m thick layer of mirabilite. This layer contains vertical conduits that allow saline pore-water to upwell onto the surface forming evaporite deposits. Near Lee’s Creek, we find evidence of high resistivities consistent with fresher groundwater as shallow as 2.8 ± 0.03 m, where increased permeability along the paleo-Jordan River corridor may provide a path for groundwater recharge from the Wasatch Mountains. Full article

The observed shortage of water resources in the western and southern regions of the Russian Federation may soon affect the territory of the Republic of Bashkortostan. An increase in the share of groundwaters can help to solve this problem. To provide the population of the republic with water resources, the groundwater of magnesium–bicarbonate-type from the Kraka ophiolite massifs can be used. The massifs occur on the western slope of the Southers Urals. In this work we studied ultramafic rocks and their influence on the formation of the chemical composition of water. The research area is located in the northern part of the Zilair synclinorium, which occurs within the Central Ural megazone. In terms of hydrogeology, of particular importance to the territory of the synclinorium is the Zilair basin of fracture waters of the second order, which is part of the Uralian hydrogeologic folded zone. The ultramafic rocks from the studied area have consistently high CaO/Al₂O₃ ratios (0.4–1.6), which indicates the widespread development of parageneses with participation of clinopyroxene and a low degree of depletion of the primitive mantle source. Because of the complex geological structure of the area, water samples collected from both water points in the Kraka massifs, and the surrounding Early–Middle Paleozoic rocks were analyzed for major ions using a laboratory method to identify possible hydro-geochemical zoning. A statistical analysis was then conducted based on the obtained anion–cation composition data. From the viewpoint of the hydrolytic concept, the formation of the chemical composition of groundwater takes place due to the removal of Mg²⁺ from the rock-forming minerals of ultramafic rocks (olivine and pyroxene) and the supply of Na⁺, K⁺, Ca²⁺, and SO₄²⁻ Cl⁻ from atmospheric precipitations. The bicarbonate anion has a complex nature, where both biochemical processes in the soil and atmospheric precipitation play a significant role. Magnesium–bicarbonate-type of waters, due to low mineralization (to 1 g/L) and the majority of other geochemical parameters (pH of the medium, and content of Na, K, Ca, SO₄, and Cl), whose values that are within the limits set by the World Health Organization (WHO), can be used as drinking water. The increased values of total hardness (0.20–3.39 mmol/L) in accordance with the regulatory document SanPiN 1.2.3685–21, adopted by the Russian Federation, do not exceed the maximum permissible concentrations (up to 7.00 (10.00) mEq/L or 3.50 (5.00) mmol/L). The high magnesium content, in accordance with GOST (state standard) R 54316–2020, allows the magnesium–bicarbonate waters of the Kraka massifs to be classified as table mineral waters for the treatment of various diseases (including hypomagnesemia). Full article

Kumamoto is a city in Japan that relies completely on groundwater for drinking water. Groundwater in the Kumamoto region divided into shallow and deep aquifers. Around Lake Ezu, where one of Kumamoto City’s largest tap-water source wells are located, groundwater from both aquifers mixes, resulting in numerous springs. The aim of this study was to identify and quantify the relative contributions of the groundwater sources that discharge into Ezu Lake. River, lake, spring, and artesian well samples were collected every month between April 2021 and March 2022, and groundwater chemistry data for the shallow and deep aquifers were obtained from previous studies. The NO₃⁻ and SO₄²⁻ concentrations indicated three end-members: (A) high NO₃⁻ from anthropogenic sources, (B) high SO₄²⁻ from Shirakawa River water, and (C) low NO₃⁻ and SO₄²⁻ from denitrification or dilution. Mixing analysis show 60–70% from A, 17–22% from B, and 7–25% from C for the lake waters. Also, the result showed that springs in the Kami-Ezu area were dominated by shallow aquifer water, whereas artesian wells in the Shimo-Ezu area reflected deep aquifer water. This is the first time that the contributions of groundwater sources in this area have been quantified using a three-component mixing approach. Furthermore, it was estimated that Shirakawa River infiltration, including the artificial recharge project from rice paddy, contributed approximately 57% to groundwater discharge into Ezu Lake in 2020. These results provide new insights into the contribution of artificial recharge from agricultural land to groundwater. Full article

This study addresses the spatial variability of groundwater levels within a mining basin in Greece. The objective is to develop an accurate spatial model of groundwater levels in the area to support an integrated groundwater management plan. Hydraulic heads were measured in 72 observation wells, which are irregularly distributed, primarily in mining zones. Multiple geostatistical approaches are evaluated to identify an optimal model based on cross-validation metrics. We introduce a novel trend model that includes the surface elevation gradient, as well as the proximity of wells to the riverbed, utilizing a modified Box–Cox transformation to normalize residuals. The results indicate that Regression Kriging with a non-differentiable Matérn variogram outperforms Ordinary Kriging in cross-validation accuracy. The study provides maps of the piezometric head and kriging variance within a Bayesian framework, being among the first to quantify and incorporate river-distance effects within regression kriging for groundwater. Full article

Co- and post-seismic earthquake-induced hydrogeological anomalies (EQHAs) in Greece are mainly associated with moderate to strong earthquakes (M_w = 6.0–7.0), particularly when seismic intensities reach IX or above. The highest frequencies are observed in the Peloponnese and Ionian Islands, followed by Central Greece and the North Aegean, characterized by dense faulting and frequent strong earthquakes. EQHAs are classified into six main types, with hydraulic variations being the most common. About 77% of earthquakes produced only one or two types of EQHA, suggesting localized hydrogeological effects, while only a few induced multiple types. Strong events (M_w = 6.0–7.0), often historic, generated the broadest variety, highlighting the influence of local geological, hydrological, and tectonic conditions on magnitude alone. Springs and wells, representing 81% of the cases, dominate the affected systems, while lakes and rivers respond less often but significantly. Most EQHAs occur in Greece’s second seismic hazard zone (74%) due to its larger geographic area. EQHAs primarily develop in karstic and porous formations but also appear in impermeable rocks due to fracturing or karst. Larger earthquakes trigger anomalies at greater distances (>100 km). Though rarely fatal, EQHAs can damage water infrastructure, contaminate supplies, and cause shortages, underscoring the need for systematic monitoring and post-earthquake water resource management. Full article

Understanding coastal hydraulic processes is essential for sustainable coastal planning and management, especially in semi-arid regions where data scarcity represents a significant challenge. This study sought to apply the Brazilian Coastal Modelling System (SMC-Brasil) to analyse the coastal hydraulic processes present on the Brazilian semi-arid coast in Rio Grande do Norte, seeking to understand its boundary conditions given the scarcity of data and limited monitoring network. The methodological procedures followed five main stages: data collection and processing, running the models, statistical analysis, and interpretation of the results. The simulations identified wave propagation and dissipation patterns influenced by local bathymetric features such as sandy banks and submarine canyons. The modelling indicated waves with an average Hs₅₀% of 1.14 m, with dominant directions from ENE to ESE. Longitudinal flows ranged from 1 to 8 m³/h, with a predominance of east to west at medium and high tides. The modelling indicated spatial gradients of energy and sediment transport compatible with historical records and field observations. The results show that submerged relief irregularities play a central role in regional coastal dynamics, conditioning current flows and deposition. The application of SMC-Brasil has shown potential to fill monitoring gaps in regions with low infrastructure, offering affordable and effective technical support for adaptive coastal planning in the face of climate change impacts. Full article

The groundwater inverse problem has several challenges such as instability, non-uniqueness, and complexity, especially for heterogeneous aquifers. Solving the inverse problem is the traditional way to calibrate models, but it is both time-consuming and sensitive to errors in the measurements. This study explores the use of machine learning (ML) surrogate models, namely Random Forest (RF) and Extreme Gradient Boosting (XGBoost), to solve the inverse problem for the groundwater model calibration. Datasets for 20 hydraulic conductivity fields were created randomly based on statistics of hydraulic conductivity from the available data of the Northern Aquifer of Qatar, which was used as a case study. The corresponding hydraulic head values were obtained using MODFLOW simulations, and the data were used to train and validate the ML models. The trained surrogate models were used to estimate the hydraulic conductivity based on field observations. The results show that both RF and XGBoost have considerable predictive skill, with RF having better R² and RMSE values (R² = 0.99 for training, 0.93 for testing) than XGBoost (R² = 0.86 for training, 0.85 for testing). The ML-based method lowered the computational effort greatly compared to the classical solution of the inverse problem (i.e., using PEST) and still produced strong and reliable spatial patterns of hydraulic conductivity. This demonstrates the potential of machine learning models for calibrating complex groundwater systems. Full article

This study focuses on developing a climate-flood model to investigate and interpret the relationship and impact of climate on runoff/flooding at a sub-regional scale using multiple linear regression (MLR) with 30 years of hydro-climatic data for the Cross River Basin, Nigeria. Data were obtained from Nigerian Meteorological Agency (NIMET) for the following climatic parameters: annual average rainfall, maximum and minimum temperatures, humidity, duration of sunlight (sunshine hours), evaporation, wind speed, soil temperature, cloud cover, solar radiation, and atmospheric pressure. These hydro-meteorological data were analysed and used as parameters input to the climate-flood model. Results from multiple regression analyses were used to develop climate-flood models for all the gauge stations in the basin. The findings suggest that at 95% confidence, the climate-flood model was effective in forecasting the annual runoff at all the stations. The findings also identified the climatic parameters that were responsible for 100% of the runoff variability in Calabar (R² = 1.000), 100% the runoff in Uyo (R² = 1.000), 98.8% of the runoff in Ogoja (R² = 0.988), and 99.9% of the runoff in Eket (R² = 0.999). Based on the model, rainfall depth is the only climate parameter that significantly predicts runoff at 95% confidence intervals in Calabar, while in Ogoja, rainfall depth, temperature, and evaporation significantly predict runoff. In Eket, rainfall depth, relative humidity, solar radiation, and soil temperatures are significant predictors of runoff. The model also reveals that rainfall depth and evaporation are significant predictors of runoff in Uyo. The outcome of the study suggests that climate change has impacted runoff and flooding within the Cross River Basin. Full article

Intensive irrigation in arid and semi-arid regions can cause significant environmental issues, including salinity, waterlogging, and water quality deterioration. Watershed modeling helps us understand essential water balance components in these areas. This study implemented a modified SWAT (Soil and Water Assessment Tool) model tailored to capture irrigation practices within a 15,900 km² area of the Arkansas River Basin from 1990 to 2014. The model analyzed key water balance elements: surface runoff, evapotranspiration, soil moisture, lateral flow, and groundwater return flow, distinguishing between wet and dry years. Over 90% of precipitation is consumed by evapotranspiration. The average watershed water yield comprises 19% surface runoff, 39% groundwater return flow, and 42% lateral flow. Various irrigation scenarios were simulated, revealing that transitioning from flood to sprinkler irrigation reduced surface runoff by over 90% without affecting crop water availability in the intensively irrigated region of the watershed. Canal sealing scenarios showed substantial groundwater return flow reductions: approximately 15% with 20% sealing and around 57% with 80% sealing. Scenario-based analyses like these provide valuable insights for optimizing water resource management in intensively irrigated watersheds. Full article

Accurate surface water volume (SWV) estimates are crucial for effective water resource management and for the regional monitoring of hydrological trends. This study introduces a multi-resolution surface water volume estimation framework that integrates ICESat-2 altimetry, Sentinel-1 Synthetic Aperture Radar (SAR), and Sentinel-2 multispectral imagery via machine learning to improve the vertical resolution of a digital elevation model (DEM) to improve the accuracy of SWV estimates. The machine learning approach provides a significant improvement in terrain accuracy relative to the DEM, reducing RMSE by ~66% and 78% across the two models, respectively, over the initial data product fidelity. Assessing the resulting SWV estimates relative to GRACE-FO terrestrial water storage in parts of the Amazon Basin, we found strong correlations and basin-wide drying trends. Notably, the high correlation (r > 0.8) between our surface water estimates and the GRACE-FO signal in the Manaus region highlights our method’s ability to resolve key hydrological dynamics. Our results underscore the value of improved vertical DEM availability for global hydrological studies and offer a scalable framework for future applications. Future work will focus on expanding our DEM dataset, further validation, and scaling this methodology for global applications. Full article

Managing groundwater flow in crystalline basement aquifers (CBAs) remains challenging due to their dependence on secondary permeability fields characterized by high spatial variability. This study combines pumping and tracer tests to estimate the hydraulic properties and connectivity in four bedrock wells within a CBA in Southwestern Nigeria. The pumping tests caused drawdowns up to 4.13 m and 12.60 m in observation and pumping wells, with significant drawdowns only in three of four wells, revealing poor connection with the fourth well. The time-drawdown plots confirm double porosity effects suggesting fracture and matrix flow and release of water from a fractured dyke. Fracture and matrix hydraulic conductivities exceeded 7.9 × 10⁻⁷ m/s and 1.00 × 10⁻¹⁰ m/s, while the aquifer yield ranged from 0.08 to 0.34%. Groundwater flow velocity and dispersivity of 5.80 × 10⁻⁴ m/s and 2.60 m were estimated from the tracer test, while a Peclet number of 3.25 suggests dominant advective flow. Calculated sustainable yield shows that each well could provide water for up to 1600 people under controlled low pumping at 0.50 l/s with higher rates possible using larger diameter wells. These results confirm high variability in groundwater flow within CBAs, justifying the need to characterize them effectively. Full article