Spatiotemporal variations in dissolved organic matter chemistry in reservoir-river continuums formed by cascade low-head dams: A case study in southwest China.

ABSTRACT India’s Dam Safety Act (2021) stipulates the objectives and functions of the organisational entities concerned with dam safety. A time-bound action by dam owners has been mandated only with respect to (i) comprehensive dam safety evaluation, (ii) emergency action plan, and (iii) risk assessment. Exigency for these actions stem from urgency to prioritise India′s ageing dams for a satisfactory level of dam safety assurance through structural rehabilitation and/or non-structural measures. Despite earnest efforts to meet the 5-year timeline for mandated actions, the dam owners are encountering serious challenges, especially regarding the risk assessment part. Since prevailing guidelines specify a complex methodology for assessing dam risks, a rapid risk assessment approach – involving an abstract exercise of risk indexing – is being attempted as a shortcut. However, compliance in this manner fails to prioritise India‘s ageing dams for expeditious safety assurance. Demystifying the risk assessment, the paper points out an alternative pathway, which the Act itself advocates as an integration of dam safety evaluation, risk assessment, and risk management. The Paper develops an integrated framework that leverages the overlapping nature of mandated actions, in which the outcome of one action serves as input to the other, substantially simplifying overall implementation of the Act.

ABSTRACT The study investigates wetland grabbing as a distinct form of socio-ecological dispossession in the Global South through an ethnographic analysis of Loktak Lake in Manipur, Northeast India. While hydropower politics has traditionally centred on river systems, the impacts of large dams on wetland ecologies and Indigenous communities remain insufficiently theorised. Drawing on more than 110 oral-history interviews, multi-sited ethnography across 12 villages, and sustained engagement with Meetei environmental networks, the study traces how the commissioning of the Ithai Barrage in 1983 reconfigured Loktak’s hydrosocial landscape. By conceptualising wetland grabbing as the extension of water-grabbing logics into wetland ecologies, the study situates hydropower expansion within a broader shift from organic to mechanical worldviews. This shift frames wetlands not as living, relational ecologies embedded in Indigenous cosmologies, but as hydraulic infrastructures to be optimised, controlled, and commodified. The barrage’s disruption of seasonal rhythms, submergence of fertile lands, decline of migratory fish, and destabilisation of the Phumdi ecosystem sustaining the Sangai deer indicate how mechanical governance fractures organic socio-ecological relations. The study shows this mechanistic developmentalism produces livelihood precarity, cultural displacement, and environmental risk while marginalising Indigenous Peoples, thereby advancing debates on resource politics, environmental justice, and the need for ecocentric, community-centred alternatives.

Sediment discharge regulates estuarine hypoxia: Coupled mechanisms of phosphorus limitation and organic carbon burial during the Yellow River WSRS.

Contamination of aquatic ecosystems by potentially toxic elements, including heavy metals and metalloid (HMs), is a persistent environmental concern due to their toxicity, persistence, and bioaccumulation. Regulated rivers with large dam systems are particularly vulnerable because altered hydrodynamics and sediment retention promote pollutant accumulation. Here, we present a first 23-year integrated dataset (2001-2023) assessment of HMs in surface sediments of the Serbian Danube River based on 620 samples collected at ten profiles from Novi Sad to Kusjak. Concentrations of Fe, Pb, Zn, Cu, Ni, Cr, As and Cd were determined, and contamination was evaluated using the geoaccumulation index (Igeo), enrichment factor (EF), pollution load index (PLI), SQGs and toxic risk index (TRI). To move beyond routine monitoring, site-specific background values for each element were derived statistically, variability was quantified by coefficients of variation (CV), and multivariate analysis (PCA) was applied to identify geochemical patterns and distinct element behavior. Most HMs showed low to moderate levels, with localized hotspots. Igeo and EF indicated As and Cd as the most critical elements, ranging from unpolluted to locally heavily polluted conditions, whereas Cu, Zn, and Cr generally indicated moderate contamination. PLI and TRI exhibited the highest values in downstream Iron Gate Reservoir profiles highlighting dam-driven sediment trapping. Upstream profiles showed improving temporal trends, likely associated with reduced local anthropogenic inputs, whereas downstream reservoir profiles remained stable or slightly deteriorated due to dam-induced sediment trapping and long-term accumulation of contaminants.

Abstract The River Don Delta (RDB) and the adjacent estuary and land areas have significant ecological and economic value. RDB is the most eastern in the Mediterranean – Black Sea (MBS) basin delta, and it has similar problems with many other MBS deltas. So, the delta became sediment-starved due to the construction of dams upstream. Additionally, the geomorphological stability of RDB is threatened by regional climate changes over the sea and land, which became especially apparent starting from 1980th. In this study, we reconstructed suspended sediment budgets in different parts of the delta and the adjacent estuary and land areas in the period from 1944 to 2020 and analyzed the changes in the delta channel’s width and at the sea border starting from 1980th. We used the modelling framework, consisting of the modified hydrodynamic model HEC RAS and the large-scale sediment budget model, as well as satellite image analysis. We estimated suspended sediment balance in the front-delta, the delta channels, and the delta platform and at the adjacent land area for the three periods 1944–1973, 1974–1981, and 1982–2020, which are related to the construction of large dams in the River Don Basin. The sediment accumulation rates were similar to those of other MBS deltas. Suspended sediment budget dropped three times for the entire case study area from 1944–1973 to 1982–2020. At the same time, the percentage of accumulated sedimentation to the fluvial sediment delivery increased almost five times from the first to the third period. This proves that sea factors, seiches and storm surges, play a stabilizing role for the River Don Delta by increase in suspended sediment budget during the hydrological interaction of sea and river waters. Observed total annual channel width within the delta changes in line with sedimentation accumulation patterns in the delta channels for the period of environmental changes that started in 1980th. The delta’s sea border stabilizes in the period 1982–2020 due to the influence of the sea factors, seiches, and increased storm surges upon sedimentation patterns. Our findings allow us to conclude that engineering regulation of sedimentation is not necessary now in the River Don Delta.

Hydropower dams, from their construction to their operation, have well-known negative impacts on riverine fish and fishing communities. Yet, they continue to be constructed in bioculturally rich places, including the Brazilian Amazon. We investigated whether two large Amazonian dams on the Madeira River have affected the livelihoods of riverine communities by carrying out 81 in-depth interviews with local knowledge holders from 11 villages. Many of the fishers (>75%) attributed changes in both the river and its fishery to the construction of the dams. However, the perceived changes (e.g., changes to the river level) varied depending on the location of their community relative to the dams. We documented an 84% decrease in fish catch and 64% decrease in income from fishing through time. These results suggest that hydropower development has compromised the income and sustenance of local fishers, leading them to adapt their behavior, which could further compromise remaining fishing stocks.

Q-CLASS: an observation-based reconstruction dataset for streamflow at China’s large dam sites

Enhanced dam safety and resilience through revised probable maximum precipitation as insights from hydroelectric scheme in Malaysia

Impact of large dams on the hydrological and sediment transport regime in the monsoon-dominated Krishna River Basin in India

The field of environmental history in India emerged as a response to movements against forest policies and large dams in the 1970s and 1980s. Yet, anti-caste scholars and activists soon critiqued early environmental histories that portrayed colonialism as a watershed in the ecological history of South Asia without accounting for the violence of environmental exclusions along lines of caste. This review article surveys works in environmental history and engages interventions from Dalit studies to evaluate the role of caste in the colonial transformation of entangled subcontinental landscapes of forests and fields. Brahmanical and colonial demarcations of forests and fields simultaneously hinged upon oppressed caste labour while eliding Dalit and Adivasi claims to land. Taking landscape to encompass contingent webs of socio-ecological relations and contested spatial imaginaries, this article argues that the reproduction of landscapes of caste exclusion entailed material struggles over nature and the naturalisation of exclusionary landscapes. This article was published open access under a CC BY licence: https://creativecommons.org/licenses/by/4.0/ .

Abstract Native fishes face imperilment due to habitat loss and fragmentation, megadrought, invasive species, and synergies amongst threats. These threats coalesce at Glen Canyon Dam (GCD), which impounds the Colorado River to create Lake Powell, a reservoir inhabited by a suite of nonnative fishes. Water level in Lake Powell has declined precipitously due to water overallocation and megadrought, increasing the risk of nonnative fish entrainment through the dam, as the penstocks draw water from the epilimnion. Our goal was to characterize the distribution and abundance of nonnative fishes in the vicinity of GCD and identify environmental conditions that may increase entrainment. We used active and passive sampling, hydroacoustics, and acoustic telemetry to assess the distribution and abundance of fishes. When the reservoir was stratified fish remained in the epilimnion, were present near the GCD penstocks, and thus at high risk of entrainment. When the reservoir was mixed, fish generally occupied shallower, warmer areas further from GCD, but this varied among species. The distribution of nonnative fish and accompanying risk of entrainment varied by season and epilimnion depth. Retaining more water in Lake Powell to draw water from below the thermocline would reduce the risk of nonnative fish entrainment into Grand Canyon.

Man-made floods from dams are intentional for different purposes, e.g., spreading sediment and helping deltaic development. Less is known about their effects on slack-water deposits (SWDs) in downstream channels. Since the implementation of the Water and Sediment Regulation Project (WSRP) through a large dam on China’s Yellow River (YR) in 2002, the dynamic sedimentary environment of the river has undergone significant changes. To understand the sedimentary responses of the downstream channels to the man-made floods, this study was conducted following a 24-day man-made flood period in 2021 to investigate SWDs on the floodplains. Sediment samples were collected from four floodplain sites in the lowermost reach of the YR. The study showed that the median grain size (D50) of the man-made flood SWDs on the floodplains ranges from 17 to 131 μm, with an average of 44.14 μm, classifying them as fine-grained deposits. Spatially, D50 of 57.2% of the sampled SWDs exhibited an increasing trend from the riverbank to the main channel. This finding indicates that during the deposition process of floodplain floods, differences may exist in the direction perpendicular to the riverbank. Along the upstream-to-downstream direction, no obvious regularity was observed. Moreover, there is no positive correlation between sediment discharge and the average grain size of suspended sediment. These findings indicate that large man-made floods by a dam will not allow finer particles to settle. Such changes in sediment transport may have a long-term effect on Yellow River deltaic development and stability.

Morocco is one of the countries most vulnerable to the impacts of climate change. Reduced rainfall, rising temperatures and declining availability of water resources are likely to plunge the country into a situation of extreme water stress. In agriculture, water loss through evaporation is a critical issue in Morocco. Although the country currently has approximately 154 large dams, with a total storage capacity of about 20.7 billion cubic meters, significant water losses through evaporation have been reported. For instance, it is estimated that nearly one billion cubic meters of water evaporate annually from approximately 90 major dams, which together store about 13 billion cubic meters. Reducing evaporation from water bodies therefore remains a major challenge, particularly in semi-arid agricultural regions such as the Béni Mellal-Khénifra region (Morocco). Our experimental protocol presents an innovative approach to reducing the amount of water evaporated from small water bodies (irrigation ponds, swimming pools, etc.). In this context, we have adopted the photovoltaic cover approach, which not only reduces evaporation but also generates energy for various uses (pumping, lighting, localized irrigation, etc.). The experimental process used is installed at the climatological station of the Faculty of Science and Technology in Béni Mellal. It is based on two rectangular tanks of the same dimensions, one of which is covered by a solar panel, while the other remains in the open air. Parameters (water level, TDS, air temperature, water temperature, air humidity) are measured daily by hand and instantaneously by sensors.Initial results from this experimental approach show a remarkable difference between the evaporation rates of the two tanks. By way of example: over a 33-day period (from 17/04/2025 to 19/05/2025), measurements show a loss of 112.2 liters of water through evaporation in the open basin, compared with 93.72 liters in the covered basin, i.e. a difference of 18.48 liters, equivalent to a reduction in the evaporation rate of around 16.5% thanks to the photovoltaic cover. Admittedly, this percentage is greatly increased during the summer season (22/05/2025 - 22/07/2025) with a percentage of 20% due to the intense sunshine which causes great warming. In this context, we calculated the correlations between various hydro-climatic parameters to better understand the evaporation phenomenon. Predictive models were then developed using Support Vector Regression (SVR), Random Forest, and Gradient Boosting. Their performance metrics (e.g., RMSE and R 2 ) are presented in the Machine Learning section, demonstrating the models' ability to accurately capture the dynamics of evaporation under both experimental conditions. So, this new approach, which is part of the integrated management of water resources, is a promising solution with a dual role: on the one hand, it will help us generate electricity, and on the other, it will preserve the maximum amount of water stored in water bodies.

A dramatic decline in American eel Anguilla rostrata abundance led to the species being assessed as Endangered in Ontario (Canada) and the closure of fisheries. As part of efforts to recover populations, four million eels (glass eels and elvers) were batch marked and released over a five-year period (2006-2010) into the upper St. Lawrence River and Lake Ontario. Over 2019-2022, we repeated an earlier large-scale electrofishing survey of eastern Lake Ontario tributaries done to assess the distribution and survival of the released eels. A decade later, we collected two hundred and fifteen eels from 19 sites along four rivers near the release site. Eels were absent from three tributaries occupied in 2010-2011. Along the Trent River, navigational locks have likely permitted migration past seven large dams previously assessed as probably impassable. Growth of translocated eels was variable among rivers. As well, many eels were still smaller than yellow eels naturally migrating into Lake Ontario. Our study indicates high, long-term post-release survival in these rivers. However, timing of out-migration and potential for successful spawning migrations remain unknown.

The construction and maintenance of large dams require close integration between geodetic and civil engineering disciplines to ensure structural stability, operational reliability, and long-term safety. This paper reviews the role of geodetic techniques in supporting civil engineering processes throughout the planning, construction, and monitoring phases of dam projects. This paper highlights how continuous monitoring and data interpretation enable early detection of abnormal structural behavior, verification of design assumptions, and implementation of corrective measures.

In this study, the seasonal and sampling point variability of AOC(Assimilable Organic Carbon) and its influencing environmental and ecological factors were investigated and analyzed in the A Reservoir and its inflowing streams located near Daegu City. The results showed that AOC concentrations were detected at very high levels during spring and summer, and this was determined to be mainly caused by algal growth, the influx of Naturally Occurring Organic Matter (NOM), and the input of external organic matter due to rainfall. A high correlation was observed between chlorophyll-a and AOC concentrations during the period of algal occurrence, but the correlation with other water quality indicators such as Total Organic Carbon(TOC) was found to be very low. Furthermore, the change in AOC concentration resulting from the increased possibility of non-point source pollution input due to rainfall was found to be greater than the increase in AOC concentration caused by algal growth. Additionally, the AOC concentration change by sampling point showed a transversal decrease pattern from the P_1 site near the small inflowing stream to the P_3 site at the outflow, with the highest concentration detected at the P_4 site among the four investigation points. Based on these findings, this study suggests that for future water quality management strategies in water source systems like large dams, it is necessary to consider the selection of sampling sites that account for seasonal concentration changes, organic matter mobility across locations, and the potential influx of specific pollutants, along with long-term monitoring to analyze spatio-temporal variability.

Large dams have become a dominant water management strategy over the last century, but they are typically managed with limited understanding of how human responses to their construction and operation influence the achievement of water management objectives. In recent years, several behavioural response patterns to large dams in human-water systems have been identified, and quantitative models developed to capture these emergent phenomena. However, there is a gap between the understanding of these phenomena in a generalised sense and communicating their relevance to water managers in local contexts. In this study we applied a generalised human-water systems model of reservoir operations during droughts and floods to two case studies in Australia; one in the water-scarce, largely agricultural Lachlan River catchment, and the other in the coastal, highly-urbanised Hawkesbury–Nepean catchment. Modelling results coupled with a qualitative review of historical socioeconomic, hydroclimatic, and water management characteristics of each case study were compared to identify potential emergent phenomena and the characteristics contributing to their development. We found reservoir effects (where increases in water storage capacity increase vulnerability to water scarcity) and lock-in behaviours are inherent risks for large reservoirs. The levee effect, whereby infrastructure reducing the probability of flooding paradoxically increases vulnerability to floods, is a risk, particularly where urbanisation is high. Sequence effects, where measures to deal with one hydrological extreme exacerbate the effects of the other extreme, are likely when operational rules constrain the adaptation of operations to hydroclimatic conditions, or when water management interactions during drought and flood are poorly understood. Where there is economic incentive to increase water usage, supply–demand cycles and rebound effects are a risk. Sensitive downstream ecosystems and high competition for limited resources make shifts in values that redirect water management priorities (pendulum swings) more likely. Identifying these emergent phenomena and their driving characteristics can help water managers identify and focus on context-specific risks to enable a proactive management approach to current and future challenges.

The Northern European Enclosure Dam (NEED) is a hypothetical project to prevent flooding in European countries following the rising ocean level due to melting arctic glaciers. This project involves the construction of two large dams between Scotland and Norway, as well as England and France. The anticipated cost of this project is 250 to 500 billion euros. In this paper, we present the simulation of the aftermath of flooding on the European coastline caused by a catastrophic break of this hypothetical dam. From our simulation results, we can observe a traveling wave after the accident, with a velocity of approximately 45 kms per hour, raising the sea level permanently inside the dammed region. This observation implies a need to construct additional dams or barriers protecting the Netherlands’ northern coastline and the Baltic Sea’s interior. Our simulations have been obtained using the following building blocks. First, a graph transformation model was applied to generate an adaptive mesh, refined towards the seabed and the seashore topography, approximating the topography of the Earth. We employ the composition graph grammar model to break the mesh’s triangular elements without generating hanging nodes. Second, the wave equation is formulated in a spherical latitude-longitude system of coordinates and solved by a high-order time integration scheme using the generalized 훼 method. While our paper mainly focuses on the simulation of the NEED dam break, we also provide a stand-alone tool to generate an adaptive mesh of the whole Earth. We can use our software as a stand-alone package in FEniCS or other simulation software.

The 17 th ICOLD Benchmark Workshop on Numerical Analysis of Dams, held in Sofia, Bulgaria, from 9 to 12 April 2025, marked a major milestone in the ongoing international collaboration within the dam engineering community. Organized by the Bulgarian National Committee on Large Dams (BUNCOLD) and overseen by the Technical Committee A on Computational Aspects of Analysis and Design of Dams of the International Commission on Large Dams (ICOLD), the event brought together experts, researchers, and industry professionals to exchange knowledge, compare methodologies, and advance the state of the art in numerical modelling of dams. Established initially as an ad hoc committee in 1988 and later formalized as a permanent entity in 1994, the ICOLD Technical Committee A (TC-A), has played a pivotal role in introducing the application of numerical modelling in dam engineering. From the outset, the TC-A has promoted the use of computational tools not only for designing new dams but also for assessing existing structures, particularly those affected by aging phenomena or exposed to loading conditions exceeding their original design limits. In its early stages, the TC-A focused on the validation of numerical codes, many of which were developed in-house, to verify the correct implementation of theoretical formulations, especially those based on the Finite Element Method (FEM). This effort was instrumental in bridging the gap between specialists in numerical modelling and dam engineers, who were initially sceptical about the reliability of numerical analyses. With the broader availability of commercial software capable of accurately simulating complex material behaviours and interfaces, coupled with advancements in computational power, the TC-A progressively redirected its attention towards comparing modelling strategies, parameter calibration techniques, and the results of nonlinear simulations. This evolution reflects the growing need for robust and reliable modelling approaches to enhance the assessment of dam safety and structural integrity.