Free-flowing River Research Articles

Cascaded reservoirs promote phosphorus bioavailability of surface sediments in the Upper Mekong River

As a key nutrient for primary productivity in freshwater ecosystems, the effect of upper cascade reservoirs on the downstream phosphorus (P) loading is subject to an ongoing scientific debate in the Mekong River. To investigate the effects of cascade reservoirs on the forms of P and its bioavailability in surface sediment, two rounds of field research were carried out both in a free-flowing river (Nu River) and in the Upper Mekong River (Lancang River) during winter and summer. Results showed that while the P was trapped with sediments and environmental parameters changed significantly, high relative abundance of bioavailable phosphorus (BioP, generally include Fe-bound P, Al-bound P, and Organic P) in sediment was detected in reservoirs and at near the border between China and Myanmar. The increased Bio-P in reservoirs may be caused by sediments sorting, anaerobic surface sediments, appropriate temperature, longer residence time and algae-nutrient positive feedback loops. Accumulated Bio-P in sediments may elevate the phosphorus release to overlying water and exacerbate eutrophication in reservoirs. Considered the intense anthropogenic phosphorus loading, nutrients enrichment risk in the lower Mekong River should receive more attention in further research.

Multiscale morphological trajectories to support management of free-flowing rivers: the Vjosa in South-East Europe

Free-flowing rivers (FFRs) are fundamental references for river management, providing the opportunity to investigate river functioning under minimal anthropic disturbance. However, large free-flowing rivers are rare in Europe and worldwide, and knowledge of their dynamics is often scarce due to a lack of data and baseline studies. So far, their characterization is mainly grounded in the longitudinal connectivity assessment, with scarce integration of further hydro-morphological aspects, particularly concerning the processes and drivers of changes in their morphology over time scales of management relevance. This work aims to broaden the characterization of FFRs by reconstructing their catchment-scale morphological evolutionary trajectories and understanding their driving causes, to support their management better. This is achieved by integrating freely available global data including Landsat imagery and climatic reanalysis with the few locally available quantitative and qualitative information. The analysis of possible drivers of change at the catchment and reach scale assesses hydrological variability, flow regulation, land use change, sediment mining and bank protection works. We applied this approach to the Vjosa River (Albania), a model ecosystem of European significance and one of the few FFRs in Europe. The Vjosa was recently declared a Wild River National Park. We investigated its catchment-scale morphological changes over 50 years, considering four reaches of the Vjosa and four reaches of its main tributaries. Satellite imagery was analyzed taking advantage of Google Earth Engine cloud computing platform. The analysis reveals a catchment-scale response to climatic fluctuations, especially in the most natural reaches, with a significant narrowing of the active river corridor, following a flood-intense period in the early 1960s. The narrowing rate gradually decreased, from 35% before 1985 to 24% between 1985 and 2000, reaching a new equilibrium from 2000 to 2020. However, the recent trajectories of the lowland reaches have been impacted by human pressures, particularly sediment mining, which intensified after the 1990s, suggesting that these reaches may instead be far from equilibrium and adjusting to such persistent stressor. Identifying the key drivers of change and building catchment-scale knowledge of geomorphic change can inform the management of riverine protected areas, and the proposed integrated approach is a promising tool to help overcome the data scarcity typical of the limited remaining large FFRs.

Length-weight relationship and condition factor of armored catfish (Pterygoplichthys sp.) in the Grijalva and Usumacinta rivers, Mexico

Length-weight relationship and condition factor (K) are descriptors of the biology of fish populations, providing fundamental information on growth strategies, nutritional status, and reproduction. These parameters are used to compare the condition of fish populations in aquatic systems with different degrees of anthropogenic intervention. This study aimed to explore the length-weight relationship of Pterygoplichthys sp., to observe whether the physiological condition factor reveals variation from a dammed river (Grijalva) to a free-flowing river (Usumacinta). Given the physiological characteristics of armored catfish (benthic consumer, tolerance to hydrological disturbance and aquatic pollution, and wide reproductive range), we predict that this fish will have a better welfare condition in the Grijalva River than in the Usumacinta. Highest abundance of armored catfish was obtained in the Grijalva River (282 specimens). However, the largest and heaviest fish were caught in the Usumacinta River (34.4 ± 5.31 cm and 389 ± 138 g, respectively). Length-weight ratio of armored catfish showed a negative allometric growth rate in both rivers (b>3), i.e., the fish grew more in length than in weight. However, the condition factor revealed that armored catfish have better physiological conditions in the Usumacinta River. Food availability, species population density, intra- and interspecific competition probably played an important role in fish welfare. Information generated in this study can be used as a guide to analyze more detailed the populations of armored catfish, taking into consideration sex and different bodies of water, to adequately monitor the populations of Pterygoplichthys sp., in the Mexican southeast.

The social valuation of a free-flowing river: A comparative analysis between two communities using semantic networks

Los ríos de flujo libre (RFL) se caracterizan por su conectividad fluvial íntegra y por proveer múltiples beneficios a las comunidades asentadas en ellos. Sin embargo, a nivel mundial estos tipos de ríos se encuentran amenazados por la construcción de obras de infraestructura. En ocasiones, la pluralidad de valores que las comunidades le atribuyen a estos ríos no se toma en cuenta, particularmente al momento de planificar proyectos de desarrollo, lo que podría detonar conflictos ambientales. Se analizaron los valores sociales asociados con el río Los Horcones (RLH) entre dos localidades, río arriba (Las Juntas y Los Veranos) y río abajo (Boca de Tomatlán). A partir del análisis de 35 entrevistas y el uso redes semánticas, se encontró que ambas comunidades tienen un interés común por la protección y conservación del río Los Horcones. Sin embargo, se observa una ponderación diferencial de valores específicos por localidad. Río abajo (Boca de Tomatlán) predominan los valores intrínsecos y relacionales, dado que el RLH es fundamental para la diversificación de sus medios de vida. En contraste, río arriba (Las Juntas y Los Veranos) predominan los valores relacionales e instrumentales debido a la dependencia económica del turismo de naturaleza que se realiza en el RLH. El reconocimiento de la pluralidad de valores asociados con los ríos de flujo libre es esencial para la formulación de estrategias de manejo y conservación de los recursos hídricos.

Modelling remote barrier detection to achieve free-flowing river targets

Abstract Fragmentation caused by artificial barriers is one of the main stressors of rivers worldwide. However, many barrier inventories only record large barriers, which underestimates barrier numbers, and hence fragmentation. Corrected barrier numbers can be obtained via river walkovers, but these are costly and time consuming. We assessed the performance of remote sensing as an alternative to river walkovers for barrier discovery by comparing the number and location of barriers detected in the field with those detected using Google Earth imagery. Only 56% of known barriers could be detected remotely, but machine learning models predicted the likelihood of remote detection with 62-65% accuracy. Barriers located downstream were twice as likely to be detected remotely than those in the headwaters, the probability of detection diminishing by 3-4% for every decrease in Strahler stream order and for every 10km increase in distance from the river mouth. Barriers located in forested reaches were 35% less likely to be detected than those in open reaches. Observer skills also affected the ability to locate barriers remotely and detection rate varied by 11% between experienced and less experienced observers, suggesting that training might improve barrier detection. Our findings have implications for estimates of river fragmentation because they show that the most under-represented structures in barrier inventories, i.e. small barriers located in forested headwaters, are unlikely to be detected remotely. Although remote sensing cannot fully replace ‘boots on the ground’ field surveys for filling barrier data gaps, it can reduce the field work necessary to improve barrier inventories and help inform optimal strategies for barrier removal under data-poor scenarios.

Analysis of the influence of water qualities on the strength of concrete

Concrete is commonly employed in construction for its tremendous compressive strength, despite its low tensile strength. This study aimed at analyzing the strength of concrete when mixed with water of varying qualities. Before concrete is formulated, tests are done on the aggregates to ascertain the right proportions but not on water used. Dreux-Gorrise concrete formulation method was employed. CAMWATER (tap water), rain water and water from a free-flowing river was used to cast concrete samples after which it was crushed to obtain 7 and 28 day resistances. The water qualities varied were pH and hardness. Hydrochloric acid and sodium hydroxide were used to vary the pH of water. Results showed an increase in concrete strength as a function of increase in water pH. Water with a high pH resulted in concrete with an appreciable strength value while acidic water resulted in very low strength values. The usage of hard water for mixing concrete resulted in a strength value lower than with soft water. Conclusively, water quality has an effect on the strength of concrete. Therefore, it is advisable to use water with a high pH value for mixing concrete, preferring rainwater over tap water when mixing concrete due to hardness of water.

Water stagnancy and wastewater input enhance primary productivity in an engineered river system

AbstractUnder warming conditions and with increasing human perturbations, rivers across the globe are facing drastic shifts in their hydrologic regime, resulting in fragmentation and disconnection from the catchment. Subsequently, a dependency on in situ primary productivity as the source of organic matter increases and warrants detailed investigation of the nature of primary production in urbanized river systems. In this study, primary productivity was estimated at multiple locations along the continuum of an engineered (Sabarmati) and a free flowing (Mahi) river systems in India using 13C tracer incubation method. Significantly enhanced primary productivity in the riverfront (engineered construction along the Sabarmati that holds water supplied by a canal) and polluted downstream of the Sabarmati compared to free flowing Mahi was observed. It was also observed that water stagnancy, temperature, and nutrient availability were the key factors regulating the rates of primary productivity in the urban river system. The study highlights the salient features of riverine primary productivity associated with engineered modifications, which needs to be considered for future river development projects.

Lagrangian dynamics of the spring zooplankton community in a large river

Zooplankton may represent a considerable part of plankton in large rivers, but little is known about the factors that control it. We hypothesized that (1) significant longitudinal increase of zooplankton abundance, biomass, taxonomic richness, and diversity will occur along a free-flowing river section; (2) the residence time of water is more important for zooplankton population growth than environmental variables such as water temperature, oxygen saturation, and food concentration; and (3) the influence of tributaries on the longitudinal dynamics of zooplankton is insignificant or only has a local effect. A Lagrangian survey was applied in the free-flowing section of the River Elbe (Germany) in spring 2022. The abundances and biomass of the dominant rotifers as well as of cladocerans and copepods increased significantly downstream due to the population growth of zooplankton. The water residence time was the most important factor for zooplankton increment. One of the tributaries increased zooplankton abundance and biomass in the River Elbe, while other tributaries did not but the introduction of new species increased taxonomic richness and decreased the evenness of zooplankton in the main river so that diversity remained nearly constant.

Spatiotemporal variability and drivers of water microchemistry in the upper Nu-Salween river: With implications for fish habitat conservation

Microchemical maps, also known as “chemoscapes”, hold immense potential for reconstructing fish habitat utilization and guiding conservation efforts. This approach relies on matching the microchemical composition of fish calcified structures (e.g., otoliths) with the surrounding water's microchemistry. However, applying this method faces a major challenge: a clear understanding of the spatiotemporal variability and drivers of water microchemistry, particularly in vast, free-flowing river ecosystems like the Nu-Salween River, Southeast Asia's longest free-flowing river. We analyzed the spatiotemporal variability and influencing factors of water microchemistry (i.e., Na:Ca, Mg:Ca, Mn:Ca, Cu:Ca, Zn:Ca, Se:Ca, Sr:Ca, and Ba:Ca) in the upper Nu-Salween River, based on a two-year sampling. Five elemental ratios (excluding Na:Ca, Mg:Ca, and Zn:Ca) in water demonstrated significant spatiotemporal variability, with Cu:Ca having the largest spatial variation, and Mn:Ca and Sr:Ca showing the greatest temporal variation. More specifically, four elemental ratios (Cu:Ca, Se:Ca, Sr:Ca, and Ba:Ca), exhibited significant variations along the longitudinal gradient, and Mn:Ca, Cu:Ca, Sr:Ca, and Ba:Ca, showed significant differences between mainstreams and tributaries. Temporally, Mn:Ca, Cu:Ca, and Ba:Ca displayed higher values and variations during the wet season, opposing the seasonal patterns of Na:Ca, Mg:Ca, and Sr:Ca. The four-element (Ba:Ca, Sr:Ca, Mg:Ca, and Mn:Ca) forest model showed the highest classification accuracy of 93%. Linear mixed-effects models showed that spatial factors have the largest influence on the variances in water microchemistry (56.36 ± 28.64%). Our study highlights the feasibility and reliability of utilizing microchemistry to reconstruct fish habitat utilization, thereby unveiling promising avenues for a more accurate understanding of fish life history in large rivers characterized by high heterogeneity in water microchemistry. By proportionally accounting for contribution of different factors to water microchemistry variability and relating them to microchemical composition of fish calcified structures, key fish habitats (e.g., spawning grounds) and migratory routes can be more precisely identified and thus protected.

Prioritisation of Barriers According to Their Impact on Migratory Fish in the Lowland River Basin District

Artificial barriers are one of the most damaging anthropogenic factors, but are also socio-economic constructions, so the decision between removing a barrier and installing a fishway must be justified. The aim was to develop a system to quantify the amount of suitable habitat for migratory fish above barriers, to assess barriers’ passability, to prioritise them in current and historical terms and to take into account the impact of the reservoir in the selection of barrier management alternatives. For this purpose, the proportion of suitable area and the potential number of spawners were calculated separately for the flooded and free-flowing river sections above the barrier. The effect of the flooded area and fishway efficiency on the potential number of individuals was assessed and the historical importance of the areas above each barrier was evaluated. The results show that the proportion of suitable area in the total area above the barriers varies between 5 and 31%. Short river stretches of high habitat quality have a higher reproductive potential than much longer stretches of lower habitat quality. Dams with fishways can still be among the most negatively impacting barriers if they are located in the migration route of fish into a large part of the basin.

Glass eel migration in an urbanized catchment: an integral bottleneck assessment using mark-recapture

Diadromous fish such as the European eel (Anguilla anguilla L.) are hampered by a high density of barriers in estuaries and freshwater systems. Modified and fragmented waterbodies lack tidal flows, and habitat may be less accessible and underutilized compared to free-flowing rivers and estuaries. With rising sea levels and increased occurrence of droughts, the number of barriers may further increase, implying that the need to study migration in such areas may even become more urgent worldwide. To study glass eel migration and behaviour in such highly modified water systems, a mark-recapture study was carried out in the North Sea Canal (NSC) basin, which drains into the North Sea via a large sluice complex. In total, eight uniquely tagged groups (3,797 glass eels) were released near the sluice complex, and 11 groups (2,663 glass eels) were released at inland barriers upstream over a 28 km long stretch in the NSC in spring 2018. The sluice complex attracted 10.3 million glass eel and did not block or delay their immigration. The large and diurnally intensively used coastal ship locks and allowings some saltwater intrusion, efficiently facilitated glass eel migration. Once in the NSC, water outlets from adjacent polders attracted glass eels relative proportional to the discharge of pumping stations. In the NSC, average migration speeds of 0.7 km/day (max. 1.8 km/day) were measured, and this increased with higher temperatures. Redistribution of glass eel from accumulations at inland barriers to other outlet locations was observed in both upstream and downstream directions in the NSC. Passage success and residence time (‘delays’ of 4.1–13.7 days) varied between the different inland barriers. Most of the glass eel, however, appears to settle in the easily accessible habitats within the brackish NSC catchment. This study combined an integral assessment of successive bottlenecks in a modified inland water system.

Diskontinuum Gornje Neretve: gradienti taksonomske in funkcionalne raznolikosti bentoških nevretenčarjev v divji balkanski reki

Free-flowing rivers are highly valuable to understand the taxonomic and functional community structure of organisms that inhabit fluvial ecosystems. We investigated patterns of macroinvertebrate community composition and food web structure using stable isotopes (δ13C and δ15N), including potential environmental drivers, over a free-flowing river continuum in the upper course of the Neretva River in Bosnia and Herzegovina. Results showed a high taxonomic diversity, a high percentage of EPT taxa (Ephemeroptera, Plecoptera, Trichoptera), and a slightly heterotrophic ecosystem (average allochthonous assimilation = 54%). The taxonomic composition differed prominently between a tributary located upstream and the mainstem. However, we also found notable species turnover between the upper (headwater and midsection) reaches and the downstream reaches of the mainstem. Macroinvertebrate abundance and the percentage of EPT peaked downstream while midsection reaches showed the highest taxonomic richness and diversity and allochthonous assimilation. Most of the functional metrics (maximum and average trophic position and isotopic richness and evenness) showed pronounced discontinuities in their spatial patterns, which did not follow the predictions of the River Continuum Concept. These results highlight the uniqueness of this section of the Neretva, where natural discontinuities structure macroinvertebrate communities in ways and by mechanisms not captured by smooth ecological concepts.

Comparisons of Twelve Freshwater Mussel Bed Assemblages Quantitatively Sampled at a 15-year Interval in the Buffalo National River, Arkansas, USA

Historically, 23 freshwater mussel species have been documented from the Buffalo National River (BNR), a 246 km, free-flowing river in northern Arkansas. The potential threats to BNR include land use/land cover changes, eutrophication, recreation, physical habitat changes, and various climate change-related effects. Twelve quantitative mussel bed sites were established and then sampled using a stratified random sampling protocol to evaluate the long-term changes between 2006 and 2020–2021 in population and assemblage characteristics. We compared (1) overall mussel bed persistence, sampling confidence levels and study-wide relative abundances, and compared species’ size and size-frequency distributions; (2) 10 overall site assemblage variables using paired t-tests; (3) site-level mean density, richness, and diversity indices using pair-wise Mann–Whitney U statistics; and (4) assemblage composition using Non-Metric Multidimensional Scaling. The major findings included the following: (1) sampling efforts based on a targeted 80% confidence level appears relatively robust, (2) BNR mussel assemblage composition and structure were relatively stable (however, small mussel bed persistence is a concern), (3) 7 of 23 sites were outliers based on freshwater mussel composition and habitat characteristics, and (4) assemblage composition changed with three species declining (Actinonaias ligamentina, Lasmigona costata, and Ptychobranchus occidentalis) and four species increasing (Cambarunio hesperus, Cyclonaias tuberculata, Eurynia dilatata, and Venustaconcha pleasii) between monitoring events.

Integrated assessment of river development on downstream marine fisheries and ecosystems

Demands on freshwater for human use are increasing globally, but water resource development (WRD) has substantial downstream impacts on fisheries and ecosystems. Our study evaluates trade-offs between WRDs and downstream ecosystem functioning considering alternative dam and water extraction options, diverse eco-hydrological responses and catchment-to-coast connectivity. We used a data-driven ensemble modelling approach to quantify the impacts of alternative WRDs. WRD impacts varied from weakly positive to severely negative depending on species, scenario and cross-catchment synergies. Impacts on fishery catches and the broader ecosystem (including mangroves) increased with catchment developments and volume of water removed, or if flow reduced below a threshold level. We found complex, linked-catchment dependence of banana prawns on flow and floods. Economic risks for this important fishery more than doubled under some scenarios. Sawfish emerged as the most sensitive across a range of WRD scenarios. Our findings highlight the need to consider marine ecosystems and fisheries to inform sustainable management of the world’s remaining free-flowing rivers.

The Role of Geomorphology on Flood Propagation in a Large Tropical River: The Peculiar Case of the Araguaia River, Brazil

In large rivers, floods are affected by the mosaic of geomorphic and geologic settings of the fluvial corridor. Here, we assess the role of geomorphology on the downstream flood dynamics of the Araguaia River, the largest free-flowing river in Central Brazil. The study integrates and advances existing flood-type classifications. We assess the factors that govern flood hydrograph properties and their downstream propagation by using flow time series, conducting statistical analysis, and evaluating geomorphic and flood metrics. Our findings highlight the role of geomorphology in the transmission of floods. In the upper and lowermost fluvial segments, the geological characteristics of the valley are a major factor. In the intermediate section, two main factors modulate the floods. The wide and complex floodplain plays a major role through storage and buffer effect for floods, and water diversion from the main system to a huge abandoned channel by avulsion governs seasonal flow transfers. The Araguaia is the most geodiverse floodplain of the Amazon–Cerrado ecotone, and floods play a fundamental ecological role in the river–floodplain environments. The combination of diverse factors controlling the flood mechanisms has to be considered when implementing conservation plans for the fluvial corridor and effective river management strategies.

A REVIEW OF FISH DIVERSITY AND MANAGEMENT OF THE VJOSA BASIN: THE FIRST FREE FLOW RIVER PROTECTED AREA IN THE BALKANS

Vjosa River, an ecologically important area and the last Europe free-flowing river, is an essential aquatic ecosystem for the Albanian ecological, social, and cultural aspects. Fish and other aquatic species are notable among livings composition found in this region. The river environment is unfortunately seriously threatened by the excessive use of its resources, and hence, the goal of this study was to examine the status of fish biodiversity and the demands of the ecosystem for management. The Vjosa river is home of at least 34 species of fishes inhabiting the river and delta system, of which 29 are native, including eight species endemic to the Balkans. With 12 species, Cyprinidae is by far the most specious family, followed by Mugilidae (five). Salmonidae and Acipenseridae are represented by 2 species each. The remaining ten families are represented by a single species. At least four species (Pseudorasbora parva, Oncorhynchus mykiss, Carassius spp., Gambusia holbrooki) were introduced into the Vjosa basin. The lower river reach is populated by other species as European eel (Anguilla anguilla), species of Family Mugilidae (Mugil cephalus, Liza ramada, Liza salienes, and Chelon labrosus), Seabream (Sparus aurata), Seabass (Dicentrarchus labrax), Flatfish (Platichthys flesus, common sole (Solea spp.), etc., while the resident species associated with saline water include numerically prevalent with the two species Atherina boyeri and Aphanius fasciatus showing presence and significance.

Over 200,000 kilometers of free-flowing river habitat in Europe is altered due to impoundments

European rivers are disconnected by more than one million man-made barriers that physically limit aquatic species migration and contribute to modification of freshwater habitats. Here, a Conceptual Habitat Alteration Model for Ponding is developed to aid in evaluating the effects of impoundments on fish habitats. Fish communities present in rivers with low human impact and their broad environmental settings enable classification of European rivers into 15 macrohabitat types. These classifications, together with the estimated fish sensitivity to alteration of their habitat are used for assessing the impacts of six main barrier types (dams, weirs, sluices, culverts, fords, and ramps). Our results indicate that over 200,000 km or 10% of previously free-flowing river habitat has been altered due to impoundments. Although they appear less frequently, dams, weirs and sluices cause much more habitat alteration than the other types. Their impact is regionally diverse, which is a function of barrier height, type and density, as well as biogeographical location. This work allows us to foresee what potential environmental gain or loss can be expected with planned barrier management actions in rivers, and to prioritize management actions.

Are ‘free-flowing rivers’ a good idea? The challenge of removing barriers from our rivers

ABSTRACT The removal of barriers from rivers is a controversial topic. Barriers come in many forms including weirs, dams, sluices and bridges. Mills are listed in the 11th-century Domesday Book and shown on early Ordnance Survey (OS) maps, often with their use marked ‘corn’, etc. So, what are the arguments for removing them? As this article shows, these relate to the creation of more natural flow regimes and the re-establishment of a connection between the river channel and the floodplain. The most obvious practical benefit is that migratory fish will find their upstream passage easier. The disbenefits are provision of access for invasive species and the loss of flood control structures. On the River Rother in West Sussex, UK, the release of sediments stored behind weirs is a potential ecological hazard. In Britain, few barriers have been removed and instead fish ladders have been installed. In the USA and Europe, dam removal is well advanced. The European Commission (EC, 2020) aims to achieve 25,000km of ‘free-flowing rivers’ by 2030 with a focus on removing ‘obsolete barriers’.

From Watershed Moment to Hydrosocial Movement: Patagonia without Dams and The Free-Flowing Rivers Network in Chile

In this article, we examine how social movement activists draw on the hydrosocial dynamics of the watershed unit to build a river protection network in resistance to extractivist development. We apply a critically engaged activist anthropological focus, and drawing on four years of collaborative fieldwork, we describe how activists formed a hydrosocial movement to reconfigure Chile as an interconnected territory of living watersheds. In 2014, the Patagonia Without Dams movement successfully stopped the development of a mega-dam complex in Chilean Patagonia, catalyzing a major upheaval in environmental politics. The Free-Flowing Rivers Network harnessed momentum from Patagonia Without Dams and jumped scales from place-based campaigns that defend singular rivers against dams to translocal actions that protect watersheds from an array of extractive industries. We show how this movement bridged rural and urban conflict zones, seeking to protect watersheds from forms of extractivism beyond dams, including mining and irrigation projects. By focusing on the Free-Flowing River Network’s efforts to translate its political-ecological platform into policy, we show how hydrosocial territories may be established, defended, expanded, and stabilized through strategies that explicitly connect water and society.

Upland river planform morphodynamics and associated riverbank erosion: Insights from channel migration of the upper Yarlung Tsangpo river

River meandering and lateral migration, caused by riverbank erosion, is a major global threat to soil, sediment, lands, and habitats. However, compared to the densely populated lowland floodplains, the upland channel morphodynamics of free-flowing rivers in a complex high-elevation alluvial setting have received less attention. In this study, we quantitatively investigated channel morphodynamics and associated frozen bank migration in the upper Yarlung Tsangpo River in the Himalayan headwater basin from the 1980s to the 2010s. By combining remote sensing analysis with field investigations, we found mean migration rates of 244 gravel-bed river bends ranging from 1.63 m/yr in the 1980s to 2.76 m/yr in the 2010s, with a maximum rate of 18.61 m/yr. The highest migration rates were associated with bends that had a width-normalised curvature radius between 3.0 and 5.0 and a sinuosity between 1.2 and 1.5. A ∼69% increase in river-bend migration and 30% more frequent bend cutoffs coincided nicely with the rapid expansion of glacial lakes due to a ∼1 °C increase in mean annual air temperature over the past four decades. Positive correlations were observed between channel migration rate and temperature, mean glacial lake area, and runoff. These results highlight the importance of the unique channel morphodynamics and the intense lateral movements of upland rivers. The close link between these dynamics and climate change suggests that a warmer world may significantly influence bank erosion and associated ecosystem processes of upland alluvial systems, which are essential for comprehending frozen channel dynamics and developing strategies for habitat protection in uplands worldwide.