Search Results (419)

The Syrdarya Delta, located in semi-arid and arid Central Asia, is an important water source for fertile landscapes. The environmental history of the Syrdarya Delta (SD) during the 19th and 20th centuries is a diverse and understudied subject, and its natural and anthropogenic aspects changed drastically during this period. As a result of the Syrdarya Delta’s location, on the shores of the former Aral Sea, there is a vital need to expand our understanding of the phases and policies that led to the current condition. This study argues that by integrating methods from social and natural sciences and applying them to selected historical materials, among them, former classified materials from the Cold War period, we can expand our understanding regarding the extent and types of disruptions in the Syrdarya Delta ecological system. The main findings of this study show that between the second part of the 19th and the 21st centuries, a period of roughly a hundred and fifty years, the SD changed drastically in aspects of urban areas, which increased during the Soviet period, changes in land use and hydrography, with changes in the amounts, size and flowing directions of water streams in the SD. The findings also present changes in vegetative cover and amounts parallel to salinization of the soil, which increased in the 1970s–1980s, and changes in the meeting point of the former Aral Sea with the SD. The findings of the study indicate that most of these changes can be attributed to anthropogenic factors, which have taken place mainly since the 1960s–1970s under the USSR regime. As this study presents, such materials can assist in reconstructing land use and land cover from the years to which our data are limited by integrating them with modern satellite image analysis, thus being able to quantify and estimate the amounts and types of these changes regarding salinization, land use and land cover and hydrology, which are crucial for studying deltas located in arid and semi-arid landscapes, such as the SD. This study presents evidence and argues that these data are of pivotal importance and should be used when attempting to rehabilitate and manage today’s Syrdarya Delta landscapes and hydrology. Full article

(1) Background: The present study examines the effects of fire on the ecosystem services of forest ecosystems in Greece. Being a Mediterranean country, Greece has been affected by fires of increasing intensity and frequency in recent years; (2) Methods: Information was extracted from 56 articles published in the period January 1997–March 2024 that were selected after an extensive literature review; (3) Results: An increasing trend in the number of published articles over time was observed. Studies on regulating and maintenance services prevailed. The majority of studies reported on thermo-Mediterranean ecosystems, with Pinus halepensis Mill forests being the most common ecosystems affected by fires. The effects of fire were primarily negative on provisioning and cultural services, as well as on the control of erosion rates, regulation of the hydrologic cycle, atmospheric composition, and climate regulation. Most effects on plant diversity were found to be positive, while positive and neutral effects were also recorded for pollination. The most pronounced negative or positive effects were noted for the first two years after the fire. The spatial mapping of the results showed that the areas most affected by the fires in Greece are Eastern Attica, Euboea, Western Attica, and most regional units of the Peloponnese; (4) Conclusions: In the era of climate change and changing fire regimes in the Mediterranean, there is a need to further research the impact of fire on ecosystem services, as this will help in the better protection and management of the most vulnerable forest ecosystems. Full article

This study analyzes the evolution of surface water and groundwater temperatures at various depths in the sand-dune ponds of Doñana National Park (southern Spain) over eight hydrometeorological years (2016–2024). This research aims to characterize the water temperature regime, identify water temperature trends, and analyze patterns in groundwater flow dynamics. The results indicate that, in a recent dry–warm period (2020–2023), coinciding with a notable decrease in precipitation and an increase in the average air temperature in the area, there was an increase in the annual mean temperature of pond water and in shallow piezometers (~15 m depth). However, in deep piezometers, a decrease in water temperature was recorded during the dry–warm period, along with a reduction in temperature variability. A phase shift has also been observed between groundwater temperature extremes and air temperature variations, with the magnitude of this shift depending on sensor depth. These findings enable the analysis of the sensitivity of these wetlands to global environmental change and contribute to the characterization of recharge and discharge flows in the aquifer, both at local and regional scales, allowing for the evaluation of flow variability in hydrological years with below-average precipitation and above-average air temperature and shallow groundwater temperature. Full article

Flood modelling in snow-fed river basins is critical for understanding the impacts of climate change on hydrological extremes. The Zhabay River in northern Kazakhstan exemplifies a basin highly vulnerable to seasonal floods, which pose significant risks to infrastructure, livelihoods, and water resource management. Traditional flood forecasting in Central Asia still relies on statistical models developed during the Soviet era, which are limited in their ability to incorporate non-stationary climate and anthropogenic influences. This study addresses this gap by applying the Soil and Water Integrated Model (SWIM) to project climate-driven changes in the hydrological regime of the Zhabay River. The study employs a process-based, high-resolution hydrological model to simulate flood dynamics under future climate conditions. Historical hydrometeorological data were used to calibrate and validate the model at the Atbasar gauge station. Future flood scenarios were simulated using bias-corrected outputs from an ensemble of General Circulation Models (GCMs) under Representative Concentration Pathways (RCPs) 4.5 and 8.5 for the periods 2011–2040, 2041–2070, and 2071–2099. This approach enables the assessment of seasonal and interannual variability in flood magnitudes, peak discharges, and their potential recurrence intervals. Findings indicate a substantial increase in peak spring floods, with projected discharge nearly doubling by mid-century under both climate scenarios. The study reveals a 1.8-fold increase in peak discharge between 2010 and 2040, and a twofold increase from 2041 to 2070. Under the RCP 4.5 scenario, extreme flood events exceeding a 100-year return period (2000 m³/s) are expected to become more frequent, whereas the RCP 8.5 scenario suggests a stabilization of extreme event occurrences beyond 2071. These findings underscore the growing flood risk in the region and highlight the necessity for adaptive water resource management strategies. This research contributes to the advancement of climate-resilient flood forecasting in Central Asian river basins. The integration of process-based hydrological modelling with climate projections provides a more robust framework for flood risk assessment and early warning system development. The outcomes of this study offer crucial insights for policymakers, hydrologists, and disaster management agencies in mitigating the adverse effects of climate-induced hydrological extremes in Kazakhstan. Full article

The transition from a perennial to an intermittent regime in newly intermittent rivers (nIRs) negatively affects both taxonomic and functional diversity, with significant repercussions on freshwater ecosystem processes and services. However, to better understand how changes in the natural flow regime may influence the structure and functioning of freshwater ecosystems, it is fundamental to assess variations in abiotic and biotic parameters throughout the hydrological phases characterizing nIRs. For these reasons, we evaluated the temporal changes in community structure and composition during the drying phase of a Central Apennines stream (Italy) over two consecutive drought years. We demonstrated that the different hydrological regime of the pre-drought phase profoundly affected the structure and composition of freshwater communities. The reduced discharge during the low-flow conditions of 2024 led to a transition from insect- to non-insect-dominated communities, with small-sized, lentic-adapted and generalist taxa replacing rheophile and more sensitive insect taxa. We also found marked interannual differences in temporal beta diversity. However, in both years, taxa richness did not exhibit a negative stepped response pattern during the sequence of channel contraction, flow cessation and pools formation. Consequently, we can assume that in newly intermittent Apennine rivers, the response of freshwater communities to drying is strictly dependent on the local and interannual variable hydrological context. This study emphasizes the need for further investigation to better understand the ecological impacts of increasing intermittence in formerly perennial streams and rivers. Full article

The Congo River Basin is the second-largest watershed globally, flowing through nine countries before reaching the Atlantic Ocean. The Kasai River Basin (KARB), containing about one-fourth of Congo’s freshwater resources, plays a strategic role in sustaining navigation, food production, and hydroelectricity generation in Central Africa. This study applies a multi-model framework suited for data-scarce regions to assess climate change impacts on water availability in the KARB. Using two conceptual hydrological models calibrated with four reanalysis datasets and fed with bias-corrected outputs from 19 climate models under two representative climate pathways (RCPs), we project changes in the mean annual discharge ranging from −18% to +3%, highlighting the sensitivity of impact assessments to model and input data choices. Additionally, streamflow signatures (Q10, Q50, Q90) are projected to decline by approximately 9%, 18%, and 13%, respectively, under RCP 8.5. Annual hydropower potential is estimated to decrease by 14% and 5% under RCPs 4.5 and 8.5, respectively. These findings provide actionable insights for water management practices in the KARB, including guiding the development of adaptive strategies to optimize water allocation, mitigate risks of scarcity, and support sustainable agricultural and industrial activities in the region. Full article

This national-scale assessment explores the anticipated impact of climate change on stream temperature in Poland. Utilizing an ensemble of six EURO-CORDEX projections (2006 to 2100) under Representative Concentration Pathways (RCPs) 4.5 and 8.5, the study employs the Soil and Water Assessment Tool (SWAT) to simulate stream temperature regimes. Validation against observed stream temperatures at 369 monitoring points demonstrates the reliability and accuracy of the SWAT model performance. Projected changes in air temperature reveal distinct seasonal variations and emission scenario dependencies. The validated stream temperature model indicates a uniform warming tendency across Poland, emphasizing the widespread nature of climate change impacts on aquatic ecosystems. Results show an increase in country-averaged stream temperature from the baseline (16.1 °C), with a rise of 0.5 °C in the near future (NF) and a further increase by 1 °C in the far future (FF) under RCP4.5. Under RCP8.5, the increase is more pronounced, reaching 1 °C in the NF and a substantial 2.6 °C in the FF. These findings offer essential insights for environmental management, emphasizing the need for adaptive strategies to mitigate adverse effects on freshwater ecosystems. However, as a preliminary study, this work uses a simplified temperature model that does not account for detailed hydrological processes and spatial variability, making it a good starting point for more detailed future research. Full article

Growing human demands are placing significant pressure on groundwater resources, causing declines in many regions. Identifying areas where groundwater levels are declining due to human activities is essential for effective resource management. This study investigates the influence of land use and land cover, crop types, and precipitation patterns on groundwater level trends across the Mississippi River Watershed (MRW), USA. Groundwater storage changes from 2003 to 2015 were estimated using data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. A spatiotemporal analysis was conducted at four scales: the entire MRW, groundwater regimes based on groundwater level change rates, 31 states within the MRW, and six USGS hydrologic unit code (HUC)-2 watersheds. The results indicate that the Lower Mississippi region experienced the fastest groundwater decline, with a Sen’s slope of −0.07 cm/year for the mean equivalent water thickness, which was attributed to intensive groundwater-based soybean farming. By comparing groundwater levels with changes in land use, crop types, and precipitation, trends driven by human activities were identified. This work underscores the ongoing relevance of GRACE data and the GRACE Follow-On mission, launched in 2018, which continues to provide vital data for monitoring groundwater storage. These insights are critical for managing groundwater resources and mitigating human impacts on the environment. Full article

Ecological flow refers to the minimum amount of water that must be maintained in a body of water to protect and preserve aquatic ecosystems. This article aims to analyze the function of ecological flow to address the reproduction of the natural hydrological regime of the San Rodrigo River, Coahuila, Mexico. A quantitative methodology was used where the ecological flow was determined based on the Mexican Standard NMX-AA-159-SCFI-2012 considering the period from 1962 to 2016. The maximum data allows us to identify runoffs of low magnitude of 6.65–15.60, those with an average trend close to 500 Mm³, and floods of extraordinary volume (namely, those 844–1260 and 1670 Mm³) with a frequency of every 35 years. Likewise, the river marks drastic changes in the flow in certain years, ranging from 0.64 to 1260 Mm³, so that the rate of variation would possibly exceed several orders of magnitude scaled in an annual phase. In conclusion, this calculation indicates that the body of water may have the function of environmental conservation covered throughout the year, with the data suggesting that in the short term the river will recover part of the water that passed through its course and thus avoid its deterioration. Full article

In the context of ongoing environmental changes, particularly against the backdrop of global warming, significant attention is being given to areas of exceptional natural value that, in many aspects, retain a pristine character. One such area is the Biebrza River in northeastern Poland, which, together with the wetlands in its basin, forms one of the most valuable ecosystems of its kind in Europe. This study analyses the changes in the thermal and ice regime for two hydrological stations, Sztabin and Burzyn, in the period from 1959 to 2023. It was found that the average annual water temperature in this period for the Biebrza River increased by 0.28 °C/decade, and in the case of ice phenomena, statistically significant changes for both stations showed a decline, with an acceleration of the ice cover disappearance by an average of 3 days/decade. These recorded changes should be considered unfavourable, as they will affect the transformation of both the biotic and abiotic characteristics of the river itself, as well as the natural elements associated with it. Full article

In this study, we visualize and analyze the literature on the Brahmaputra river using a spectral clustering algorithm, tracking research trends over time. We found that the focus of research on the Brahmaputra has changed over time in the last decade, with a shift from geology to hydrology and geochemistry and a rapid growth in climate change research in recent years. In the future, potential hot topics may be “water resource management” and other topics related to transboundary water resource management and cooperation. At the same time, this study also analyzes in detail the keywords and clusters “geohydrology” and “ecological risk and sustainable development”, among other topics. We believe that future research should carefully consider the potential effects of transdisciplinary research trends. For instance, it is urgent that transborder governance and management regimes be renovated through joint efforts and cross-border effective actions carried out by multifaceted and multi-scalar agencies along this river. Full article

Lake ecosystems are impacted by anthropogenic disturbances and have become vulnerable worldwide. Highly disturbed lake ecosystems are not well understood due to the lack of data on changes in the structures and functions of ecosystems. In this paper, we focus on Lake Baiyangdian (BYDL), the largest shallow lake in North China. Following the establishment of the Xiong’an New Area (XNA) in 2017, concerted efforts to restore BYDL’s aquatic environment have been undertaken, which has led to significant changes in the structures and functions of the ecosystems. We evaluated the biomass dynamics of main biological communities and detected the regime shifts of environmental factors in BYDL from 2016 to 2023. Further, we constructed a food web model for the BYDL ecosystem in 2023 by using Ecopath with Ecosim (EwE) and made a comparison with the reported results in 2018. The results showed significant changes in the ecosystem structure of BYDL over the last 6 years. In 2023, the submerged macrophytes biomass in the system increased by 4.2 times compared to 2018, leading to an increase in total system throughput. We found that BYDL changed from an algal-type lake to a macrophyte-dominated lake. In addition, we found TN, NH₄⁺-N, and COD_Mn were significantly decreased in BYDL during the restoration. TN and NH₄⁺-N had a change point in approximately 2021, indicating that a regime shift had occurred during restoration. Overall, the BYDL ecosystem was in an immature but developing state, as indicated by ecological network analysis indicators. Nutrient-loading reduction, hydrological regulation, and rational biomanipulation may be the potential driving factors of change in the BYDL ecosystem. We strongly recommend the timely harvesting of submerged macrophytes, the proliferation and release of herbivorous fishes, and the assessment of the ecological capacity of carnivorous fishes in the future ecological restoration of BYDL. Full article

Mangrove restoration efforts have increased in order to help combat their decline globally. While restoration efforts often focus on planting seedlings, underlying chronic issues, including disrupted hydrological regimes, can hinder restoration success. While improving hydrology may be more cost-effective and have higher success rates than planting seedlings alone, hydrological restoration success in this form is poorly understood. Restoration assessments can employ a functional equivalency approach, comparing restoration areas over time with natural, reference forests in order to quantify the relative effectiveness of different restoration approaches. Here, we employ the use of baseline community ecology metrics along with stable isotopes to track changes in the community and trophic structure and enable time estimates for establishing mangrove functional equivalency. We examined a mangrove system impacted by road construction and recently targeted for hydrological restoration within the Rookery Bay National Estuarine Research Reserve, Florida, USA. Samples were collected along a gradient of degradation, from a heavily degraded zone, with mostly dead trees, to a transition zone, with a high number of saplings, to a full canopy zone, with mature trees, and into a reference zone with dense, mature mangrove trees. The transition, full canopy, and reference zones were dominated by annelids, gastropods, isopods, and fiddler crabs. Diversity was lower in the dead zone; these taxa were enriched in ¹³C relative to those found in all the other zones, indicating a shift in the dominant carbon source from mangrove detritus (reference zone) to algae (dead zone). Community-wide isotope niche metrics also distinguished zones, likely reflecting dominant primary food resources (baseline organic matter) present. Our results suggest that stable isotope niche metrics provide a useful tool for tracking mangrove degradation gradients. These baseline data provide critical information on the ecosystem functioning in mangrove habitats following hydrological restoration. Full article

Artificial objects, particularly tunnels used for water transport under pressure, impact the geological and hydrogeological environment to a greater or lesser extent, and it is vital to assess their contributions to groundwater quality. Although tunnels are typically lined with concrete, their interaction with the hydrogeological environment intensifies over time. In this study, the detailed spatiotemporal monitoring of all hydrogeological features within the potential influence zone of the hydraulic tunnel of the Pirot Hydropower Plant has been conducted in order to determine the degree of interaction between the artificial object and the natural environment in real time, and to assess the correlation between monitored parameters. Natural conditions of the environment were defined, as well as potential changes through the observing groundwater regimes. The monitoring network included observations of groundwater regimes at seven springs located in close proximity to the hydraulic tunnel, within the tunnel, at three piezometers, and along the river, while methods employed were hydrological monitoring, physicochemical monitoring, and groundwater piezometer sensing. Cross-correlation analysis has been applied for assessing the impact of precipitation dynamics on the spring discharge regime. The results indicate a direct influence of the tunnel on the hydrogeological environment, proving the consistency and high correlation between the monitored parameters. Full article

Climate change is expected to significantly impact temperature and precipitation, as well as snow accumulations and melt in mid-latitudes, including in the Baltic region, ultimately affecting the quantity and seasonal distribution of streamflow. This study aims to investigate the changes in the magnitude and timing of annual maximum discharge for 30 hydrological monitoring stations across Latvia from 1950/51 to 2021/22. Circular statistics and linear mixed effects models were applied to identify the strength of seasonality and timing. Trend analysis of the magnitude and timing of flood peaks were performed by using the Theil–Sen method and Mann–Kendall test. We analyzed regional significance of trends across different hydrological regions and country using the Walker test. Results indicate strong seasonality in annual flood peaks in catchments, with a single peak occurring in spring in the study sub-period of 1950/51–1986/87. Flood seasonality has changed over recent decades (i.e., 1987/88–2021/22) and is seen as a decrease in spring maximum discharge and increase in winter flood peaks. Alterations in annual flood occurrence also point towards a shift in flow regime from snowmelt dominated to mixed snow–rainfall dominated, with consistent changes towards the earlier timing of the flood peak, with a more or less pronounced gradation from west to east. Analysis shows that a significant trend of decrease in the magnitude and timing of annual maximum discharge was detected. Full article