Search Results (589)

Mires are fragile ecosystems in which plant communities are structured by complex interactions among hydrological regimes and groundwater properties. Although extensively studied in boreal and temperate regions, their environmental drivers in southern European mountains remain poorly understood. We investigated five complex mires in the Pyrenees, sampling 156 plots of vascular plants and bryophytes while measuring water table dynamics and groundwater chemistry over two years. Vegetation was classified into six main groups, including acid and alkaline fens, transition mires and Sphagnum hummocks. Ordination analyses (tb-PCA and RDA) revealed that mean water table depth, groundwater calcium and silicon content, and pH were the most important determinants of floristic composition. Bryophytes responded primarily to pH, whereas vascular plants were more influenced by water table variables, reflecting functional trait differences. Despite these environmental effects, spatial structure explained a comparable or greater proportion of variance, especially for vascular plants, underscoring the roles of local species pools, dispersal limitation, and site history in shaping community patterns. Establishing a reliable baseline is crucial for interpreting the distribution patterns of mire vegetation. Our results demonstrate that both environmental gradients and spatial processes are fundamental to understanding mire vegetation and highlight the importance of analyzing plant taxonomic groups separately. Full article

Soil secondary salinization is a major limiting factor of sustainable agricultural production in arid and semi-arid irrigation zones, yet predictive tools for regional water–salt dynamics remain limited. The Yichang Irrigation District, located within the Hetao Irrigation Area, has experienced persistent salinity challenges due to shallow groundwater tables and intensive irrigation. In this study, we aimed to simulate long-term soil water–salt dynamics in the Yichang Irrigation District and evaluate the effectiveness of different engineering and management scenarios using the SaltMod model. Field monitoring of soil salinity and groundwater levels during summer and fall (2022–2024) was used to calibrate and validate SaltMod parameters, ensuring accurate reproduction of seasonal soil salinity fluctuations. Based on the calibrated model, ten-year scenario simulations were conducted to assess the effects of changes in soil texture, irrigation water quantity, water quality, rainfall, and groundwater table depth on root-zone salinity. Our results show that under baseline management, soil salinity is projected to decline by 5% over the next decade. Increasing fall autumn leaching irrigation further reduces salinity by 5–10% while conserving 50–300 m³·ha⁻¹ of water. Sensitivity analysis indicated groundwater depth and irrigation water salinity as key drivers. Among the engineering strategies, drainage system improvement and groundwater regulation achieved the highest salinity reduction (15–20%), while irrigation regime optimization provided moderate benefits (~10%). This study offers a quantitative basis for integrated water–salt management in the Hetao Irrigation District and similar regions. Full article

The present study was undertaken for six years to appraise the responses of four-year-old established grapevines (Vitis vinifera L., cv. Perlette) to saline–sodic groundwater irrigation in relation to different amendments in a field experiment on non-saline, non-sodic calcareous sandy loam soil under a semi-arid climate at the research farm of Punjab Agricultural University, Regional Research Station, Bathinda, Punjab, India. Different water quality treatments, viz., canal water or good-quality water (GQW), poor-quality saline–sodic groundwater (PQW), alternate irrigation of canal water and groundwater (GQW/PQW), PQW with 50% gypsum (CaSO₄·2H₂O) requirement (PQW + GR₅₀), PQW with 100% gypsum requirement (PQW + GR₁₀₀), and PQW with sulphitation pressmud (by-product of sugar industry) @ 6.6 t ha⁻¹ on a dry weight basis (PQW + SPM), applied in furrows, were imposed in quadruplicate with a randomized block design. PQW with an electrical conductivity (EC) of 2.2–2.4 dS m⁻¹, residual sodium carbonate (RSC) content of 6.21–6.44 mmolc L⁻¹, and a sodium adsorption ratio (SAR) from 23.1 to 24.8 (mmolc L⁻¹)^0.5 was used during the course of experimentation. The pooled mean 6-year data showcased that the treatments GQW/PQW, PQW + GR₅₀, PQW + GR₁₀₀, and PQW + SPM improved the berry yield by 28.3%, 11.3%, 21.2%, and 31.0%, respectively, when compared with PQW. Use of amendments, i.e., gypsum, sulphitation pressmud, and practice of GQW/PQW for irrigation in a cyclic mode, helped in reducing the pH, SAR, and bulk density (BD) of surface soil (0–15 cm) and enhancing the final infiltration rate (FIR) of soil and berry yield. A maximum water use efficiency (WUE) of 3.99 q ha⁻¹-cm was recorded in the GQW treatment, followed by 3.93, 3.72, and 3.68 q ha⁻¹-cm in the PQW + SPM, GQW/PQW, and PQW + GR₁₀₀ treatments, respectively. Application of amendments alongside PQW evidenced a significant enhancement in total soluble solids (TSSs) and a decrease in the acidity of berries as compared to PQW. These results suggest that table grape yield (cv. Perlette) on calcareous sandy loam soil under saline–sodic groundwater irrigation can be sustained with the application of PQW + GR₁₀₀, sulphitation pressmud, and GQW/PQW in already-established grapevines with minimal detrimental effects on soil health. Full article

Over the past two decades, climate change and climatic variability have received significant attention from the scientific community. The present study investigates the impact of future climate change on irrigation water requirements in the coastal districts of Odisha, Eastern India, specifically within the Phulnakhara distributary’s command area of the main Puri canal system. Field investigations were conducted during the kharif and rabi seasons of 2019–2020 and 2020–2021. The study offers a new perspective involving a future climate data-driven model with water requirements of RCP 4.5 for this canal command area, and after integrating this with the optimal cropping area, the optimal future irrigation water needs for the kharif and rabi seasons were determined. The study focused on assessing future irrigation water demands under changing climatic conditions, with an emphasis on the conjunctive use of surface and groundwater resources. Projections indicate that peak irrigation demand will occur in the kharif season of 2042–2043 and the rabi season of 2044–2045. Furthermore, a significant decline in groundwater levels is anticipated, ranging from 1.23 to 1.42 m below ground level (BGL) during the kharif season and from 1.46 to 1.64 m BGL during the rabi season, over the next 30 years (2021–2022 to 2050–2051). The most pronounced groundwater table decline is projected for the years 2042–2043 (kharif) and 2044–2045 (rabi), highlighting the need for sustainable water resource management strategies in the region. Based on this study, integrating the optimal crop area with future irrigation water needs will result in groundwater table fluctuations under the permissible limit. Full article

To understand how phreatophytes correspond to groundwater dynamics in arid regions, it is important to examine the specific water use patterns in different habitats. In this study, we investigated whether and how saltcedar (Tamarix ramosissima Ledeb.) responded in its water use patterns to the changing groundwater table during the growing season in two contrasting habitats (i.e., riparian and dune sites). δ¹⁸O and δ²H values of xylem sap and four potential water sources (i.e., shallow, middle, and deep soil water, and groundwater) were measured to determine the water-use pattern. Comparisons of the water sources in different habitats indicated that the depths of water extraction by saltcedar were shallower in the riparian habitat than in the dune habitat. During the growing season, saltcedar in the diparian habitat consistently extracted soil water from a depth of 30−60 cm (volumetric water content: 18.2 ± 3.5%), which was recharged by groundwater. In contrast, the saltcedar in the dune habitat either extracted soil water from a deeper depth (below 100 cm, volumetric water content: 5.8 ± 1.2%) that was also supposed to be recharged by groundwater, or directly used groundwater. These results suggest that the primary water source for saltcedar was from deeper groundwater during the growing season and did not change with the groundwater fluctuation. Full article

Groundwater flow systems (GFSs) and associated distribution of travel times provide critical insight into the regional subsurface hydrology, especially in arid regions experiencing intensive groundwater use. This study examines the impact of large-scale irrigation pumping on GFS patterns in the arid Kongqi River Basin, China. A three-dimensional (3D) steady-state groundwater flow model was constructed using MODFLOW, and flow paths were delineated through particle tracking to quantify travel time and residence time distributions. Two scenarios with and without pumping were compared. Results show that groundwater abstraction significantly alters GFS patterns, lowering water tables in pumping zones while raising them in irrigation areas fed by surface water. This hydrologic redistribution fragments recharge and discharge zones, particularly under the influence of evapotranspiration (ET) from shallow groundwater. Simulated travel times range up to ~506 ka, with median values decreasing from 9.7 ka (no-pumping) to 8.3 ka (pumping). Both travel time distribution (TTD) and residence time distribution (RTD) exhibit power-law characteristics, reflecting the dominance of slow flow paths in deep GFSs. While the modeling results provide valuable insight into current regional groundwater flow, it does not account for transient flow effects and hydrodynamic dispersion of solutions. Future research should incorporate groundwater isotope data to validate the model and assess time-dependent changes in GFSs. Full article

Spilled hydrocarbons released from oil pipeline accidents can result in long-term environmental contamination and significant damage to habitats. In this regard, evaluating actions in response to vulnerability scenarios is fundamental to emergency management and groundwater integrity. To this end, understanding the trajectories and their influence on the various parameters and characteristics of the contaminant’s fate through accurate numerical simulations can aid in developing a rapid remediation strategy. This paper develops a numerical model using the CactusHydro code, which is based on a high-resolution shock-capturing (HRSC) conservative method that accurately follows sharp discontinuities and temporal dynamics for a three-phase fluid flow. We analyze nine different emergency scenarios that represent the breaking of a diesel oil onshore pipeline in a porous medium. These scenarios encompass conditions such as dry season rupture, rainfall-induced saturation, and varying pipeline failure pressures. The influence of the spilled oil pressure and water saturation in the unsaturated zone is analyzed by following the saturation contour profiles of the three-phase fluid flow. We follow with the high-accuracy formation of shock fronts of the advective part of the migration. Additionally, the mass distribution of the expelled contaminant along the porous medium during the emergency is analyzed and quantified for the various scenarios. The results obtained indicate that the aquifer contamination strongly depends on the pressure outflow in the vertical flow. For a fixed pressure value, as water saturation increases, the mass of contaminant decreases, while the contamination speed increases, allowing the contaminant to reach extended areas. This study suggests that, even for LNAPLs, the distribution of leaked oil depends strongly on the spill pressure. If the pressure reaches 20 atm at the time of pipeline failure, then contamination may extend as deep as two meters below the water table. Additionally, different seasonal conditions can influence the spread of contaminants. This insight could directly inform guidelines and remediation measures for spill accidents. The CactusHydro code is a valuable tool for such applications. Full article

Soil salinity and sodicity are escalating global threats to agricultural productivity, severely limiting crop yield and quality. In the Igdir Plain of Türkiye, high summer temperatures, minimal precipitation, and a shallow groundwater table have intensified salinity-related challenges, currently affecting one-third of the arable land. Despite the substantial impact of salinity stress on eggplant (Solanum melongena L.) production, studies addressing plant tolerance mechanisms under real field conditions remain limited. In this study, eggplant was cultivated in eight distinct soil classes under open-field conditions to evaluate the effects of soil salinity and saline-alkalinity on morphological, physiological, and biochemical traits. Increasing soil exchangeable sodium percentage (ESP) and electrical conductivity (ECe) levels significantly suppressed plant height, root length, stem diameter, and leaf area, along with over 90% reductions in shoot and root biomass. Salinity impaired the uptake of essential nutrients (Ca, K, P, and Fe), while promoting toxic Na⁺ accumulation in leaves. This ionic imbalance induced oxidative stress, as indicated by elevated malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and antioxidant enzyme activities (SOD, CAT, APX), all of which were strongly correlated with proline accumulation. The results highlight a coordinated plant response under salinity stress but also reveal the insufficiency of natural defense mechanisms under high salinity levels. Unless supported by external interventions to improve stress resilience and ensure productivity, growing eggplant in saline–alkaline soils should be avoided. Full article

The commented paper uses arbitrary and unsubstantiated hypotheses to attribute land subsidence phenomena in the Amyntaion basin to the operations of the Public Power Corporation (PPC) surface coal mine, disregarding, or at least grossly underestimating, the effect of about 600 pumped deep wells for irrigation purposes all over the basin. In addition to the huge difference in the pumped quantities of water from the aquifer, ground water table lowering due to the PPC mine has negligible influence at distances over 500 m from the edge of the mine, while the areas examined in the paper are at distances of several kilometers from the edge of the mine. Furthermore, the authors attribute the landslide that occurred in the mine in 2017 to the steep excavation slopes of the mine and the increased groundwater pore pressure due to reduced peripheral pumping, which is completely inaccurate. To build their case, the authors of the commented paper disregard multiple references in research publications on the above issues, as explained in the main text of this discussion. Full article

Due to increased precipitation intensity and sea-level rise, low-lying coastal roads are increasingly vulnerable to subbase saturation. Widely applied lumped hydrological approaches cannot accurately represent time and space-varying groundwater levels in some highly conductive coastal soils, calling for more sophisticated tools. This study assesses the suitability of the Gridded Surface Subsurface Hydrologic Analysis model (GSSHA) for representing hydrological processes and groundwater dynamics in a unique coastal roadway setting in Alabama. A high-resolution model was developed to assess a 2 km road segment and was calibrated for hydraulic conductivity and aquifer bottom levels using observed groundwater level (GWL) data. The model configuration included a fixed groundwater tidal boundary representing Mobile Bay, a refined land cover classification, and an extreme precipitation event simulation representing Hurricane Sally. Results indicated good agreement between modeled and observed groundwater levels, particularly during short-duration high-intensity events, with NSE values reaching up to 0.83. However, the absence of dynamic tidal forcing limited its ability to replicate certain fine-scale groundwater fluctuations. During the Hurricane Sally simulation, over two-thirds of the segment remained saturated for over 6 h, and some locations exceeded 48 h of pavement saturation. The findings underscore the importance of incorporating shallow groundwater processes in hydrologic modeling for coastal roads. This replicable modeling framework may assist DOTs in identifying critical roadway segments to improve drainage infrastructure in order to increase resiliency. Full article

Prolonged inundations are altering coastal forest ecosystems of the southeastern US, causing extensive tree die-offs and the development of ghost forests. This hydrological stressor also alters carbon fluxes, threatening the stability of coastal carbon sinks. This study was conducted to investigate the interactions between hydrological drivers and ecosystem responses by analyzing daily eddy covariance flux data from a wetland forest in North Carolina, USA, spanning 2009–2019. We analyzed temporal patterns of net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (RE) under both flooded and non-flooded conditions and evaluated their relationships with observed tree mortality. Generalized Additive Modeling (GAM) revealed that groundwater table depth (GWT), leaf area index (LAI), NEE, and net radiation (Rn) were key predictors of mortality transitions (R² = 0.98). Elevated GWT induces root anoxia; declining LAI reduces productivity; elevated NEE signals physiological breakdown; and higher Rn may amplify evapotranspiration stress. Receiver Operating Characteristic (ROC) analysis revealed critical early warning thresholds for tree mortality: GWT = 2.23 cm, LAI = 2.99, NEE = 1.27 g C m⁻² d⁻¹, and Rn = 167.54 W m⁻². These values offer a basis for forecasting forest mortality risk and guiding early warning systems. Our findings highlight the dominant role of hydrological variability in ecosystem degradation and offer a threshold-based framework for early detection of mortality risks. This approach provides insights into managing coastal forest resilience amid accelerating sea level rise. Full article

For effective groundwater resource management, it is essential to model the dynamic behaviour of aquifers in response to rainfall. Here, a methodological approach using a recurrent neural network, specifically a Long Short-Term Memory (LSTM) network, is used to model groundwater levels of the shallow porous aquifer in Southern Italy. This aquifer is recharged by local rainfall, which exhibits minimal variation across the catchment in terms of volume and temporal distribution. To gain a deeper understanding of the complex interactions between precipitation and groundwater levels within the aquifer, we used water level data from six wells. Although these wells were not directly correlated in terms of individual measurements, they were geographically located within the same shallow aquifer and exhibited a similar hydrogeological response. The trained model uses two variables, rainfall and groundwater levels, which are usually easily available. This approach allowed the model, during the training phase, to capture the general relationships and common dynamics present across the different time series of wells. This methodology was employed despite the geographical distinctions between the wells within the aquifer and the variable duration of their observed time series (ranging from 27 to 45 years). The results obtained were significant: the global model, trained with the simultaneous integration of data from all six wells, not only led to superior performance metrics but also highlighted its remarkable generalization capability in representing the hydrogeological system. Full article

Groundwater systems are intrinsically linked to climate, with changing conditions significantly altering recharge, storage, and discharge processes, thereby impacting water availability and ecosystem integrity. Critical knowledge gaps persist regarding groundwater equilibrium timescales, water table dynamics, and their governing factors. This study develops a novel remote sensing framework to quantify factor controls on groundwater–climate interaction characteristics in the Heihe River Basin (HRB). High-resolution (0.005° × 0.005°) maps of groundwater response time (GRT) and water table ratio (WTR) were generated using multi-source geospatial data. Employing Geographical Convergent Cross Mapping (GCCM), we established causal relationships between GRT/WTR and their drivers, identifying key influences on groundwater dynamics. Generalized Additive Models (GAM) further quantified the relative contributions of climatic (precipitation, temperature), topographic (DEM, TWI), geologic (hydraulic conductivity, porosity, vadose zone thickness), and vegetative (NDVI, root depth, soil water) factors to GRT/WTR variability. Results indicate an average GRT of ~6.5 × 10⁸ years, with 7.36% of HRB exhibiting sub-century response times and 85.23% exceeding 1000 years. Recharge control dominates shrublands, wetlands, and croplands (WTR < 1), while topography control prevails in forests and barelands (WTR > 1). Key factors collectively explain 86.7% (GRT) and 75.9% (WTR) of observed variance, with spatial GRT variability driven primarily by hydraulic conductivity (34.3%), vadose zone thickness (13.5%), and precipitation (10.8%), while WTR variation is controlled by vadose zone thickness (19.2%), topographic wetness index (16.0%), and temperature (9.6%). These findings provide a scientifically rigorous basis for prioritizing groundwater conservation zones and designing climate-resilient water management policies in arid endorheic basins, with our high-resolution causal attribution framework offering transferable methodologies for global groundwater vulnerability assessments. Full article

The main goal of our work was to evaluate approaches for modeling lateral outflow from shallow unconfined aquifers in a one-dimensional model of vertical variably-saturated flow. The HYDRUS-1D model was modified by implementing formulas representing lateral flow in an aquifer, with linear or quadratic drainage functions describing the relationship between groundwater head and flux. The results obtained by the modified HYDRUS-1D model were compared to the reference simulations with HydroGeoSphere (HGS), with explicit representation of 2D flow in unsaturated and saturated zones in a vertical cross-section of a strip aquifer, including evapotranspiration and plant water uptake. Four series of simulations were conducted for sand and loamy sand soil profiles with deep (6 m) and shallow (2 m) water tables. The results indicate that both linear and quadratic drainage functions can effectively capture groundwater table fluctuations and soil water dynamics. HYDRUS-1D demonstrates notable accuracy in simulating transient fluctuations but shows higher variability near the surface. The study concludes that both quadratic and linear drainage boundary conditions can effectively represent horizontal aquifer flow in 1D models, enhancing the ability of such models to simulate groundwater table fluctuations. Full article

Groundwater is the primary water source for ecosystems, and so changes in groundwater levels, if directional and constant, can cause changes in vegetation and habitat characters. In Białowieża National Park, a significant decline in the water table was observed at the beginning of the 20th century. The question therefore arose as to whether the changes that occurred at that time were permanent. A second question was whether the negative trend would continue so clearly in the following years. The study is based on measurements from 1985 to 2005 and 2022 to 2023 taken in the same monitoring wells. Complete data were collected from 21 monitoring wells. An analysis of groundwater levels between 1985 and 2005 showed an average decline of 0.08 m/10 years in swamp habitats, 0.11 m/10 years in moist habitats, and 0.21 m/10 years in fresh habitats. The measurements in 2022 and 2023 showed that the trend of falling water levels had slowed down in almost the entire study area, with water levels in recent years being similar to those at the beginning of the century. This was also confirmed by comparing years with similar precipitation: 2022 with 1986, and 2002, 2004, and 2023 with 1999. This was due to the higher precipitation after 2005. In the period of 2006–2023, precipitation in the hydrological years was on average 60 mm higher than in the period of 1985–2005. Despite the clear trend toward rising air temperatures, the higher precipitation compensated for the higher evapotranspiration. However, one area showed a systematic decrease in water levels. This occurred at the watershed of the two largest rivers in the Białowieża Forest. The findings indicate that watershed areas are most vulnerable to lowering the groundwater level due to climatic warming. Full article