Search Results (605)

With rapid socioeconomic development and intensified human activities, nitrogen (N) loads have continued to rise, exerting significant impacts on the environment. Most existing studies focus on single cities or short time periods, which limits their ability to capture nitrogen dynamics under rapid urbanization. Based on statistical data from multiple cities in Zhejiang Province from 2011 to 2021, this study applied nitrogen balance accounting and statistical analysis to systematically evaluate the spatiotemporal variations in nitrogen inputs, outputs, and surpluses, as well as their driving factors. The results indicate that although nitrogen inputs and outputs fluctuated over the past decade, the overall nitrogen surplus showed an increasing trend, with the nitrogen surplus per unit area rising from 49.89 kg/(ha·a) in 2011 to 62.59 kg/(ha·a) in 2021. Zhejiang’s nitrogen load was higher than the national average but remained below the levels of highly urbanized regions such as the Yangtze River Delta and Pearl River Delta. Accelerated urbanization and increasing anthropogenic pressures were identified as major contributors to the rising nitrogen surplus, with significant inter-city disparities. Cities like Hangzhou, Ningbo, Wenzhou, and Jinhua were found to face higher risks of nitrogen pollution. Redundancy analysis and Pearson correlation analysis revealed that nitrogen surplus was positively correlated with cropland area, livestock population, total population, precipitation, GDP, and industrial output, further highlighting the dominant role of human activities in nitrogen cycling. This study provides the long-term quantitative assessment of nitrogen balance under multi-city coupling at the provincial scale and identifies key influencing factors. These findings provide scientific support for integrated nitrogen management across multiple environmental compartments in Zhejiang Province, including surface water, groundwater, agricultural systems, and urban wastewater, under conditions of rapid urbanization. Full article

This study integrates 90 years of hydrometeorological observations (1930/31–2019/20) with end-century projections (2080–2099) to evaluate climate-driven changes in the water balance of the Nitra River basin (2094 km²), Slovakia. Despite a modest 2–3% increase in annual precipitation from 1930/31–1959/60 to 1990/91–2019/20, mean annual runoff declined from 229 mm to 201 mm (≈−12%), primarily due to enhanced evapotranspiration stemming from a +1.08 °C basin-wide temperature increase. An empirical regression from 90 hydrological years shows that +100 mm in precipitation boosts runoff by ≈41 mm, while +1 °C in temperature reduces it by ≈13 mm. The BILAN monthly water balance model was calibrated for 1930/31–2019/20 to decompose runoff components. Over the 90-year period, the modeled annual runoff averaged 222 mm, comprising a 112 mm baseflow (50.4%), a 91 mm interflow (41.0%), and a 19 mm direct runoff (8.6%), underscoring the key role of groundwater and subsurface flows in sustaining streamflow. In the second part of our study, the monthly water balance model BILAN was recalibrated for 1995–2014 to simulate future runoff under three CMIP6 Shared Socioeconomic Pathways. Under the sustainability pathway SSP1-1.9 (+0.88 °C; +1.1% precipitation), annual runoff decreases by 8.9%. The middle-of-the-road scenario SSP2-4.5 (+2.6 °C; +3.1% precipitation) projects a 17.5% decline in annual runoff, with particularly severe reductions in autumn months (September −32.3%, October −35.8%, December −40.4%). The high-emission pathway SSP5-8.5 (+5.1 °C; +0.4% precipitation) yields the most dramatic impact with a 35.2% decrease in annual runoff and summer deficits exceeding 45%. These results underline the extreme sensitivity of a mid-sized Central European basin to temperature-driven evapotranspiration and the critical importance of emission mitigation, emphasizing the urgent need for adaptive water management strategies, including new storage infrastructure to address both winter floods and intensifying summer droughts. Full article

Based on GRACE RL06 data, this study reconstructs a monthly Terrestrial Water Storage Anomaly (TWSA) series in Shandong Province (2003–2024) using Singular Spectrum Analysis (SSA) and derives Groundwater Storage Anomaly (GWSA) via the water balance equation. The spatiotemporal evolution characteristics of GWSA were systematically examined, and the relative contributions of climatic factors and human activities to groundwater storage changes were quantitatively assessed, with the aim of contributing to the development, utilization, and protection of groundwater in Shandong Province. The results indicate that temporally, GWSA in Shandong Province exhibited a statistically significant decreasing trend at a rate of −8.45 mm/a (p < 0.01). The maximum GWSA value of 17.15 mm was recorded in 2006, while the Mann–Kendall abrupt change-point analysis identified 2013 as a significant transition point. Following this abrupt change, GWSA demonstrated a persistent decline, reaching the minimum annual average of −225.78 mm in 2020. Although moderate recovery was observed after 2020, GWSA values remained substantially lower than those in the pre-abrupt change period. Seasonal analysis revealed a distinct “higher in autumn and lower in spring” pattern, with the most pronounced fluctuations occurring in summer and the most stable conditions in winter. Spatially, approximately 99.1% of the study area showed significant decreasing trends, displaying a clear east–west gradient with more severe depletion in inland regions compared to relatively stable coastal areas. Crucially, human activities emerged as the dominant driving factor, with an average contribution rate of 86.11% during 2003–2024. The areal proportion where human activities served as the decisive factor (contribution rate > 80%) increased dramatically to 99.58%. Furthermore, the impact of human activities demonstrated bidirectional characteristics, transitioning from negative influences during the depletion phase to positive contributions promoting groundwater recovery in recent years. At present, the GWSA in Shandong Province is expected to continue declining in the future, with an overall downward trend. Countermeasures must be implemented promptly. Full article

Groundwater resources are scarce in the cold and arid regions of north China. Moreover, regional water resource replenishment without external sources remains difficult. This water deficit has become a major factor restricting the sustainable development of regional vegetable production. The effective utilization of rainwater harvesting for irrigated agricultural production is necessary to suppress droughts and floods in farming under the semi-arid climate of this area in order to both guarantee a stable supply of vegetables to the market in south and north China and promote the balanced development of regional agriculture–resource–environment integration. In this study, based on continuous simulation and Python modeling, we simulated and analyzed the water supply and production effects of irrigation with harvests and stored rainwater on tomatoes under different water supply scenarios from 1992 to 2023. We then designed and tested a water-saving and high-yield project for rainwater-irrigated greenhouses in 2024 and 2025 under natural rainfall conditions in northwestern Hebei Province based on the reference irrigation scheme. The water supply satisfaction rate, water demand satisfaction rate, and volume of water inventory of tomato fields under different water supply scenarios increased with the rainwater tank size, and the corresponding drought yield reduction rate of tomato decreased. Under the actual rainfall scenarios in 2024 and 2025, a 480 m² greenhouse with a 14.4 m³ rainwater tank for producing tomatoes irrigated with rainwater drip from the greenhouse film collected 127.7 and 120.5 m³ of rainwater, respectively. The volume of the rainwater tank was exceeded 8.3 and 8.0 times, and up to 93.8% and 95.0% of the irrigated groundwater was replaced; additionally, the average yield of the small-fruited tomato ‘Beisi’ was 50,076.6 kg·hm⁻² and 48,110.2 kg·hm⁻², reaching 96.1% and 92.3% of the expected yield. Conclusion: The irrigation strategy based on the innovative “greenhouse film–rainwater harvesting–groundwater replenishment” model developed in this study has successfully achieved a high substitution rate of groundwater for greenhouse tomato production in the cold and arid regions of north China while ensuring stable yields by mitigating drought and waterlogging risks. This model not only provides a replicable technical framework for sustainable agricultural water resource management in semi-arid areas but also offers critical theoretical and practical support for addressing water scarcity and ensuring food security under global climate change. Full article

Freshwater scarcity increasingly constrains agricultural sustainability and global food security, particularly where crop production and trade shape national water balances. This study quantifies Ecuador’s green (soil moisture/rainfall) and blue (surface and groundwater) virtual water flows associated with seven strategic crops (banana, cocoa, pineapple, maize, rice, barley and potato) from 2000 to 2023 using the Hoekstra–Mekonnen accounting framework, and FAOSTAT production and bilateral trade data. Furthermore, Logarithmic Mean Divisia Index (LMDI) decomposition analysis was applied to identify the key drivers influencing virtual water trade, including economic growth, population, product structure, and water intensity. Results reveal that Ecuador operates as a persistent net exporter of virtual water, with export flows dominated by green water, reflecting the country’s reliance on rainfall-supported production. Virtual water exports increased from 3000 to >15,000 Mm³·yr⁻¹ over the study period, while imports remained substantially smaller, confirming Ecuador’s structurally export-oriented agricultural economy. The LMDI outcomes show that export growth is driven primarily by economic expansion (8.28 × 10⁸ m³) and shifts in the crop export mix, partially offset by improvements in water intensity. These findings highlight Ecuador’s vulnerability to trade-related water pressures and demonstrate the value of virtual water indicators for guiding water governance and SDG-aligned trade strategies, thereby promoting the decoupling of economic growth from water resource consumption and connecting virtual water trade to domestic water scarcity. Full article

The behavior of the carbon cycle within the Land-Ocean Aquatic Continuum (LOAC) is shaped not only by aquatic processes but also by chemical interactions occurring at the atmosphere–water interface. In particular, the transport of acid rain precursors such as SO₂ and NO_x to surface waters via deposition can alter the water’s pH balance, thereby affecting Dissolved Inorganic Carbon (DIC) fractions and CO₂ emission potential. In this study, air quality measurements from three monitoring stations (Bosna, Karatay, and Meram) in Konya province of Türkiye, along with precipitation and temperature data from a representative meteorological station for the period 2021–2023, were analyzed using the Mann–Kendall Trend Test. Additionally, seasonal pH values of groundwater were examined, and their trends were compared with those of the other variables. The findings reveal striking differences on a station basis. At the Bosna station, while NO (Z = 10.80), NO₂ (Z = 9.47), and NO_x (Z = 10.04) showed strong increasing trends, O₃ decreased significantly (Z = −15.14). At the Karatay station, significant increasing trends were detected for CO (Z = 10.01), PM₁₀ (Z = 8.59), SO₂ (Z = 5.55), and NO_x (Z = 2.44), whereas O₃ exhibited a negative trend (Z = −6.54). At the Meram station, a significant decrease was observed in CO (Z = −11.63), while NO₂ showed an increasing trend (Z = 3.03). Analysis of meteorological series indicated no significant trend in precipitation (Z = −0.04), but a distinct increase in temperature (Z = 2.90, p < 0.01). These findings suggest that the increasing NO_x load in the Konya atmosphere accelerates O₃ consumption and, combined with rising temperatures, creates a potential for change in the carbon chemistry of aquatic systems. The results demonstrate that atmospheric pollutant trends constitute an indirect but significant pressure factor on the aquatic carbon cycle in semi-arid regions and highlight the necessity of integrating atmospheric processes into carbon budget analyses within the scope of LOAC. Full article

The Hailiutu River Basin in northern China represents a semi-arid area where groundwater-dependent ecosystems (GDEs) play a critical role in maintaining regional vegetation structure and ecological stability. This study investigated the spatiotemporal dynamics of GDEs and their relationship with water conditions using trend analysis, partial correlation, and Random Forest models over the period of 2002–2022. The results show that vegetation activity (NDVI) increased at a rate of 0.0052/yr in GDEs. Precipitation exhibited a basin-wide upward trend of 0.735 mm/yr, while SPEI increased at 0.0207/yr. In contrast, groundwater storage declined markedly at −11.19 mm/yr, highlighting a persistent reduction in water availability that poses a significant risk to the stability of GDEs. Both partial correlation analysis and the random forest model consistently showed strong ecohydrological interactions between vegetation and groundwater. Vegetation dynamics are primarily driven by groundwater availability, especially in groundwater-dependent ecosystems. Conversely, groundwater variations are most strongly influenced by vegetation. The results indicate that precipitation and the standardized precipitation–evapotranspiration index (SPEI) are the primary positive drivers of interannual NDVI variability, whereas groundwater plays a critical role in sustaining GDEs. Field observations of key species confirm the dependence of GDEs on groundwater, and vegetation dynamics are regulated by climate and groundwater; however, ongoing groundwater decline may threaten ecosystem stability. These findings demonstrate that vegetation transpiration exerts the dominant influence on groundwater variations, while groundwater simultaneously constrains vegetation growth, particularly in areas where declining groundwater storage anomalies (GWSAs) coincide with reduced NDVI. The results emphasize that continuous groundwater depletion threatens vegetation–groundwater sustainability, highlighting the need for balanced groundwater and vegetation management in arid regions. Full article

Increasing levels of chloride in surface water are associated with detrimental effects on water quality, aquatic ecosystems, infrastructure, and human health. Numerous mass-balance studies have inferred watershed transport processes by interpreting chloride inputs and outputs, but few represent internal dynamics explicitly. We constructed a coupled water/chloride mass balance model to gain insights into storage, residence time, and transport processes in a 10-km² urban watershed. The model, which operates over a 10-year period at a daily time scale, represents storage in a dynamic soil-moisture reservoir, quick-flow runoff from storm events, and slow-flow runoff that sustains streamflow in dry weather. The calibrated model accurately represented (a)the observed transition from a streamflow enrichment regime in cold months to a dilution regime in warmer months, (b) the observed tendency for late-summer concentrations to be higher after winters with heavy snowfall, and (c) a period-of-record downward trend in chloride concentration likely associated with a downward trend in annual snowfall. Estimated chloride inputs averaged 195 metric tons per year, while the average output was 270 metric tons per year. In contrast, estimated storage was only 107 metric tons. The estimated mean residence time in groundwater was 1.27 years. This short residence time indicates that efforts to reduce inputs will manifest as decreased concentrations in streamflow on a management-relevant time scale of several years. The coupled mass balance model yielded insights into internal watershed dynamics that would not be possible from simple input/output analysis; such models can be useful tools for gaining insight into small watershed hydrology and pollutant transport. Full article

This study investigates the propagation of climate model variability to coastal groundwater systems under the high-emission RCP8.5 scenario, focusing on the Almyros Basin in Greece. Using Med-CORDEX bias-corrected climate projections, an Integrated Modelling System (IMS) combines UTHBAL (surface hydrology) and MODFLOW (groundwater hydrology) to simulate future conditions, including precipitation, temperature, evapotranspiration, groundwater recharge, water balance, and seawater intrusion (as a quantity). The analysis quantifies both central tendencies and inter-model spread, revealing substantial declines in groundwater recharge and intensified seawater intrusion, while highlighting the uncertainty introduced by climate model projections. These findings provide critical insights for adaptive water resource management and planning in Mediterranean coastal aquifers under climate change. Full article

Lithium (Li) is a critical metal element in geothermal systems, yet its enrichment mechanism in coastal geothermal waters remains poorly understood. This study focuses on the Xiamen coastal geothermal system, located in the South China granitic reservoir at the front of the Pacific subduction zone. Self-organizing map (SOM) classification, hydrogeochemical analysis, hydrogen–oxygen isotopic constraints, and a three end-member mass balance model were applied to identify the sources and enrichment mechanisms of Li. The geothermal waters are classified into two types: inland low-TDS (Cluster-1) and coastal high-TDS (Cluster-2). Isotopic data indicate a mixture of meteoric water and seawater as the recharge source. The model shows that seawater and groundwater mixing accounts for 2–45% of Li concentration, with over 55% derived from the rock end-member. The leaching of 0.002–0.187 kg of granite per liter of geothermal water explains the observed Li levels. Elevated temperature and low pH enhance Li⁺ release from silicate minerals, and reverse cation exchange further amplifies this process. A strong positive correlation between the CAI-II index and Li⁺ concentration reveals a synergistic effect of ion exchange in high-salinity environments. Overall, the results provide a quantitative framework for understanding Li enrichment and evaluating resource potential in coastal geothermal systems. Full article

Soil salinization poses a major threat to agricultural sustainability in arid regions worldwide, where it is intrinsically linked to irrigated agriculture. In these water-scarce environments, the equilibrium of the water and salt balance is easily disrupted, causing salts to accumulate in the root zone and directly constraining crop growth, thereby creating an urgent need for precise water and salt management strategies. While precise water and salt transport models are essential for prediction and control, their accuracy is often compromised by parameter uncertainty. To address this, we developed a lumped water–salt balance model for the Hetao Irrigation District (HID) in China, integrating farmland and non-farmland areas and vertically structured into root zone, transition layer, and aquifer. A novel calibration approach, combining random sampling with Kernel Density Estimation (KDE), was introduced to identify optimal parameter ranges rather than single values, thereby enhancing model robustness. The model was calibrated and validated using data from the Yichang sub-district. Results showed that the water balance module performed satisfactorily in simulating groundwater depth (R² = 0.79 for calibration, 0.65 for validation). The salt balance module effectively replicated the general trends of soil salinity dynamics, albeit with lower R² values, which reflects the challenges of high spatial variability and data scarcity. This method innovatively addresses the common challenge of parameter uncertainty in the model, narrows the parameter value ranges, enhances model reliability, and incorporates sensitivity analysis (SA) to identify key parameters in the water–salt model. This study not only provides a practical tool for managing water and salt dynamics in HID but also offers a methodological reference for addressing parameter uncertainty in hydrological modeling of other data-scarce regions. Full article

Identifying the dominant mechanisms of water and soil salinization in arid and semi-arid endorheic basins is fundamental for our understanding of basin-scale water–salt balance and supports water resources management. In many inland basins, mineral dissolution, evaporation, and transpiration govern salinization, but disentangling these processes remains difficult. Using the Barkol Basin in northwestern China as a representative endorheic system, we sampled waters and soils along a transect from the mountain front through alluvial fan springs and rivers to the terminal lake. We integrated δ¹⁸O–δ²H with hydrochemical analyses, employing deuterium excess (d-excess) to partition salinity sources and quantify contributions. The results showed that mineral dissolution predominated, contributing 65.8–81.8% of groundwater salinity in alluvial fan settings and ~99.7% in the terminal lake, whereas direct evapoconcentration was minor (springs and rivers ≤ 4%; lake ≤ 0.2%). Water chemistry types evolved from Ca-HCO₃ in mountainous runoff, to Ca·Na-HCO₃·SO₄ in groundwater and groundwater-fed rivers, and finally to Na-SO₄·Cl in the terminal lake. The soil profiles showed that groundwater flow and vadose-zone water–salt transport control spatial patterns: surface salinity rises from basin margins (<1 mg/g) to the lakeshore and is extremely high near the lake (23.85–244.77 mg/g). In spring discharge belts and downstream wetlands, the sustained evapotranspiration of groundwater-supported soil moisture drives surface salt accumulation, making lakeshores and wetlands into terminal sinks. The d-excess-based method can robustly separate the salinization processes despite its initial isotopic variability. Full article

Sustainable agriculture in semi-arid regions like the Awash Basin is critically dependent on water availability, which is increasingly threatened by rapid land use and land cover (LULC) change. This study assesses the impact of multi-decadal LULC changes on water resources essential for agriculture. Using satellite-derived LULC scenarios (2001, 2010, 2020) to drive the WRF-Hydro/Noah-MP modeling framework, we provide a holistic assessment of water dynamics in Ethiopia’s Awash Basin. The model was calibrated and validated with observed streamflow (R² = 0.80–0.89). Markov analysis revealed rapid cropland expansion and urbanization (2001–2010), followed by notable woodland recovery (2010–2020) linked to national initiatives. Simulations show that early-period changes increased surface runoff, potentially enhancing reservoir storage for large-scale irrigation. In contrast, later changes promoted subsurface flow, indicating a shift towards enhanced groundwater recharge, which is critical for small-scale and well-based irrigation. Evapotranspiration (ET) trends, validated against GLEAM (monthly R² = 0.88–0.96), reflected these shifts, with urbanization suppressing water fluxes and woodland recovery fostering their resurgence. This research demonstrates that land use trajectories directly alter the partitioning of agricultural water sources. The findings provide critical evidence for designing sustainable land and water management strategies that balance crop production with forest conservation to secure irrigation water and support initiatives like Ethiopia’s Green Legacy Initiative. Full article

Mine closure by flooding initiates hydrogeological changes that affect land stability, soil moisture, and surface ecosystems, further shaped by regional climatic trends that increase pressure on water resources. This study examines the Olkusz–Pomorzany mine (Poland), flooded between 2021 and 2022, focusing on the links between groundwater rebound, land movement, and environmental transformation after closure. This analysis combines EGMS-based land movement (2018–2023), groundwater levels (2022–2024), meteorological records (1981–2024), and Sentinel-2-derived Normalized Difference Vegetation Index, Normalized Difference Water Index, and Moisture Index time series (2016–2024). Land cover changes were assessed using Sentinel-2 data for 2019–2024. Results show climate-driven subsidence of less than 1 mm/year across the area and a shift to uplift within the mining zone, with maximum groundwater rebound of 103 m in the central depression cone and uplift of up to 3.6 mm/year. Climatic water balance remained negative, with Vertical Water Exchange averaging −11.6 mm/month in 2022–2024. Hydrospectral indices indicate seasonal variability and modest increases in vegetation activity and moisture after flooding. Land cover analysis shows an expansion of surface water and wetlands where historical drainage and rebound overlap. These findings confirm that groundwater recovery is already reshaping surface conditions and highlight the need for integrated monitoring in post-mining areas. Full article

The extraction of lithium from salt flats such as the Salar de Atacama (SdA) has raised concerns about its potential impact on the local water balance. This study evaluates the possibility of including localized mining impacts on groundwater tables, lagoons, brine–freshwater mixing, evaporation, precipitation feedback, and recharge in a localized water footprint case study of lithium mining in the SdA. Using ready-to-use hydrogeological models, we primarily assessed the effects of lithium extraction on groundwater levels, evaporation, precipitation, and basin recharge dynamics. The influence on evaporation and recharge appears to be limited, with surplus evaporation due to mining accounting for a maximum of 4% of basin-wide evaporation. Regarding groundwater tables, drawdown exceeding 25 cm to several meters has largely been confined to areas that are not critical for local ecosystems. Available hydrogeological models have also helped to estimate whether the extraction of freshwater by mining companies can exacerbate groundwater drawdown during brine extraction. Consequently, non-overlapping, geographically distinct depression cones have been identified, but total water consumption by all users in the basin has not been considered. Furthermore, the aspect of model uncertainty requires further investigation, as do changes in lagoon areas and brine–freshwater mixing, which are not yet comprehensively captured by existing models. Full article