Transboundary River Research Articles

Remote sensing insights into water allocation and evaporation challenges in the Hirmand River Basin, after the operation of Kamal Khan Dam

Study RegionThe Hirmand River Basin is a vital transboundary river system, that originates in Afghanistan’s Hindu Kush Mountains and flows into the Sistan Depression, and encompassing the Chah Nimeh Reservoirs in Iran and the Godzareh Depression in Afghanistan. Study FocusThe Kamal Khan Dam, constructed on the Hirmand River in Afghanistan, has significantly altered the downstream water direction and distribution between the Chah Nimeh Reservoirs and Godzareh Depression. Utilizing remote sensing techniques, particularly Landsat 8 satellite imagery and the FAO 56 PM as a evaporation retrieval method, the research focuses on evaluating changes in water allocation and evaporation rates in these regions over the past decade. New Hydrological Insights for the RegionThe findings reveal that after operation of the Kamal Khan Dam, water allocation to the Chah Nimeh Reservoirs has drastically decreased, leading to a 54 % reduction in their average area from 2020–2023 compared to the previous years. Conversely, the Godzareh Depression, now receiving the redirected water, has experienced significantly higher evaporation rates, contributing to substantial water losses. These changes underscore the critical need for effective water management strategies to address the escalating water scarcity and hydrological imbalances in this arid region.

Reassessing water resource challenges in a changing climate in the Kagera transboundary river basin, Tanzania

The dynamic shifts in climatic patterns, particularly alterations in precipitation, have significantly impacted water resource availability and accessibility. These climate-induced changes affect hydrological processes, encompassing runoff, groundwater replenishment, water demand, and biophysical patterns within river basins. This study seeks to unravel the multifaceted implications encountered and challenges in water resource management within the river basin. It employed a survey-based approach for data collection, including Key informant interviews (KI), consultation methods and documentary reviews. The study utilized Statistical Package for the Social Sciences (SPSS) and Microsoft Excel for quantitative analysis and thematic synthesis for qualitative insights, including local community perspectives. The findings reveal substantial fluctuations in precipitation, protracted droughts, severe flooding, and other climatic extremes. The observed annual mean rainfall of 832 mm, with a standard deviation of 248, a standard error of 361, and a skewness of −945, accentuates the pronounced variability in mean precipitation, exhibiting a declining trend indicative of climatic shifts (R2 = 0.1797 and P = 0.002). The challenges are limited access to hydrological and meteorological data, undermining prediction accuracy, infrastructure planning, and response strategies for water resource allocation and management. The absence of unified approaches, influenced by the politics of riparian states, feeble coordination, conflicting sectoral policies, and ambiguous priorities, hinders effective transboundary water resource management. The study addresses these complexities and advocates for institutionalizing robust water management strategies that capitalize on existing resources and foster innovative capacities among critical stakeholders. Central to these efforts is harmonizing and enforcing policies, regulations, and laws governing water use, coupled with a concerted focus on inclusive governance to ensure the sustainability of water resource management. Such effort entails synchronized strategies, programs, plans, and livelihood practices underpinned by active stakeholder involvement in pivotal facets of water resources management.

Spatio-temporal Situation, Regional Differences, and Dynamic Evolution of the Distribution of Ecological Compensation in the Yellow River Basin

In the context of regional coordinated development and modernization of ecological and environmental governance capacity, the spatial collaborative governance of transboundary river basins has received extensive attention, but the ecological compensation of river basins is faced with the intertwined relationship of rights and responsibilities, and the horizontal ecological compensation mechanism has not yet been perfected. Based on the emergy ecological footprint model, the ecological compensation amount of 90 cities in the Yellow River Basin in 2007-2021 was measured, and the spatiotemporal pattern, regional differences, and dynamic evolution characteristics of distribution were explored by combining exploratory spatial data analysis, Dagum Gini coefficient, kernel density estimation, and spatial Markov chain analysis. The results showed that： ① The spatiotemporal pattern of ecological compensation in the Yellow River Basin was different, the ecological compensation amount decreased slightly in the fluctuation and increased from the northwest to southeast gradient in general, and the high-value areas were concentrated in the areas with a superior ecological background or developed economy, and some upstream cities had given up many development opportunities to maintain the ecological security of the Yellow River Basin, however, failed to obtain reasonable ecological compensation. ② A significant positive spatial agglomeration phenomenon was observed in ecological compensation and the overall spatial distribution trend was "cold in the north and hot in the south." The number of low-payment areas and low-compensation areas gradually decreased, showing a gradually shrinking agglomeration layout from the periphery to the center, whereas the number of high-payment areas and high-compensation areas continued to increase and formed a spatial evolution characteristic of the coexistence of scattered distribution and group distribution. ③ The overall regional differences in ecological compensation expanded. The over-variation density was the main source of the overall differences, and the focus on alleviating the intra-regional and inter-regional differences was located in the downstream areas. ④ A slight multi-level differentiation phenomenon was present in ecological compensation. The influence of different neighbors on the horizontal transfer of ecological compensation was quite different. This spatial spillover effect easily formed a "space club convergence" phenomenon within a certain geographical spatial range, but with the expansion of time, the probability of maintaining the original level of ecological compensation in each city decreased, and mobility gradually increased. Therefore, increasing the investment in ecological compensation in different fields, strengthening the coordinated development between regions, and giving full play to the spatial spillover effect are important ways to solve the current spatial imbalance of ecological compensation in the Yellow River Basin.

India-Bangladesh Conflict: An Overview

Abstract: The India-Bangladesh conflict primarily revolves around historical, territorial and resource-related disputes that have shaped the bilateral relationship between the two neighbouring South Asian countries. Emerging from the Partition of British India in 1947 and the subsequent creation of East Pakistan (now Bangladesh), tensions escalated during the 1971 Bangladesh Liberation War, which resulted in Bangladesh's independence with Indian military support. Key areas of conflict have included the demarcation of borders, particularly over the disputed enclaves, the maritime boundary in the Bay of Bengal, and the sharing of transboundary river waters, such as the Ganges and the Teesta. While the Land Boundary Agreement of 2015 resolved several border issues, the water-sharing disputes remain unresolved, particularly concerning the Teesta River, which is critical to Bangladesh’s agriculture. Additionally, non-traditional security concerns such as illegal migration, cross-border insurgencies, and trafficking continue to challenge bilateral relations. Nevertheless, India and Bangladesh have strengthened their cooperation in recent years, particularly in trade, energy and regional security, while both countries seek to balance their national interests within a framework of diplomacy and economic interdependence. This overview highlights that while conflict persists in certain areas, India and Bangladesh have made significant strides in resolving disputes and fostering collaboration, although challenges remain in ensuring equitable resource distribution and addressing mutual security concerns.

Source distribution, ecological risks, and controlling factors of heavy metals in river sediments: Receptor model-based study in a transboundary river basin

In the context of transboundary rivers, which constitute intricate fluvial ecosystems, the persistent threat of heavy metals (HMs) contamination poses significant risks to ecosystem health. In this study, ecotoxicological hazards, governing factors, and the distribution of nine HMs (uranium (U), lead (Pb), cadmium (Cd), nickel (Ni), chromium (Cr), manganese (Mn), iron (Fe), zinc (Zn), and copper (Cu)), as well as sediment characteristics (sand, silt, clay, organic matter, and pH) are assessed within the sediment. The current investigation encompasses the analysis of twenty-seven sediment samples, utilizing inductively coupled plasma mass spectrometry, in the transboundary river basin of Bangladesh, specifically the Teesta River. Notably, the findings underscore the predominance of Cd as a contaminant, responsible for 51.85%, 81.84%, and 100% of the geo-accumulation index, contamination factor, and enrichment factor, respectively. The Teesta River emerges as moderately to highly polluted, with cumulative probabilities of 7.4%, 85.2%, and 7.4% denoting "medium", "high", and "priority" pollution levels, respectively. Regions in the upstream and downstream middle sections of the study area exhibit relatively higher pollution levels, particularly in proximity to Kaunia Upazila in the Rangpur district. Ecologically, the potential risk index indicates a low likelihood of ecological impacts at 77.8%, alongside a moderate risk observation of 22.2%. The current results attribute the distribution of these HMs to the pH and organic matter content within the sediment, serving as pivotal factors. To unravel the origins of the HMs, the positive matrix factorization (PMF) model successfully identifies four contributing factors, primarily from geogenic sources. Validation of the PMF model through Spearmen correlation and principal component analysis (PCA) reveals a consistent pattern, affirming its efficacy in this analysis. Within the region, HM sources are identified as originating from anthropogenic activities such as irrigation, industrial discharges, and domestic effluent, in addition to substantial inputs from geogenic sources. Recognizing the transboundary nature of metal pollution, the current study underscores the imperative for continuous and vigilant monitoring, coupled with the implementation of robust management practices. The interplay of both anthropogenic and geogenic factors necessitates a comprehensive approach to effectively and sustainably combat HM contamination.

Beyond international water law – unconventional approaches to conventional foundations in times of global crises

This article argues that there is a large gap between the aspirations of international water law and the management of transboundary rivers and lakes necessary to address the existential challenges that have arisen in the twenty-first century. In addition to this gap in practice, these include climate destruction, the holistic view of river basins which includes environmental values and social justice, a more sceptical view of large dams and diversions, and the collapse of the post-World War II idea of a global community of shared values. Thus, international water law requires a transformative change to meet these challenges. New treaties and conventions are not needed. Instead, we need to move beyond traditional international water law. We call for innovation in three main areas: (1) the prevailing approach to this area of international law should be reconceptualised to more fully embrace global issues in ways that enhance community-building approach broadly anchored in the UN Sustainable Development Goals (SDGs); (2) the normative legal framework, especially procedural obligations, needs to be enhanced, in part through a more invigorated rule of due diligence; and (3) the current regulatory silos that apply to water law need to be better integrated across the layers of international/national law to better represent and to protect the communities of the watershed across the basin.

International water conventions, the exploitation of trans-boundary rivers and the Nile water dispute among Ethiopia, Sudan and Egypt

Ethiopia, Sudan and Egypt entered into dispute since Ethiopia began the construction of the Renaissance Dam along the Blue Nile in 2011. This article is aimed at assessing the core facts about water conventions, the use of trans-boundary rivers and the main argument points of Egypt and Sudan against Ethiopia's use right of the Nile. Data were obtained from conventions and laws, study reports and television interviews. Percent and ratios were used for quantifying data. The 1997 UN Water Convention, having seven criterions for equitable water use by riparian nations, is a better platform for the negotiation on the Nile water. Ethiopia contributes 86.52 billion m3 to the Nile water although Egypt's contribution is negligible. Despite the built-up of 3 huge dams by Egypt and over 10 by Sudan, these countries aggressively contest the Renaissance Dam of Ethiopia. Egypt diverts about 46 billion m3 water for irrigation. Turk, an upstream nation (alike Ethiopia in the Nile basin), built 11 dams along the Tigris and Euphrates Rivers with rare contest from the downstream nations. The existence of ‘adequate rainfall’ and ‘other rivers’ in Ethiopia, the colonial treaties, the Nile as the only resource, and the impact of the Renaissance Dam are among the main points of argument of Egypt and Sudan against Ethiopia's use right of the Nile. The Nile water use by Ethiopia is inevitable as 73.7 % of the rivers' flow, 65.3 % of the hydropower and 50.6 % of the irrigation potential of all Ethiopian rivers is in the Nile basin; besides, significant share of the population has no electric service (>60), no pure water access (42.7 %) and is below poverty line (29.6 %). Thus, the three countries need to be flexible for the ‘give and take’ principle-based negotiation and ensuring the equitable use of the Nile water.

A synergic approach using the model and remote sensing data for flood monitoring in under-observed transboundary rivers

ABSTRACT The southern plain of Nepal recognized as the ‘granary of Nepal’, confronts recurrent monsoon-induced flooding, posing a substantial threat to its pivotal role as a major agricultural contributor to the national economy. As an analysis, this study employs advanced satellite imagery to delineate historical floods in nine flood-prone transboundary basins and compares the rainfall-induced model-based inundation in the West Rapti Basin (WRB) to validate the result. The extent of flooding was mapped between 2015 and 2022 using Sentinel-1 Synthetic Aperture Radar data processed on Google Earth Engine. Hydrodynamic modelling centred on the WRB, incorporated daily measured precipitation data with varying return periods over a 10 m resolution digital elevation model generated through an in situ survey. The model was calibrated for the August 2017 flood event with Nash–Sutcliffe efficiency greater than 70% and validation reasonably with satellite-derived flood maps with Cohen's Kappa value of 0.58 and an overall accuracy metric of 0.84. This synergic approach integrates climatology, remote sensing data, and hydraulics to monitor transboundary river floods in Nepal where precise hydro-meteorological data are limited, thus, offering continuous all-weather monitoring.

A Comparative Study of High-level Classification Algorithms for Land Use and Land Cover Classification and Periodic Change Analysis Over Transboundary Ruvu River Basin, Tanzania

A Comparative Study of High-level Classification Algorithms for Land Use and Land Cover Classification and Periodic Change Analysis Over Transboundary Ruvu River Basin, Tanzania

Changes in the air temperature regime across the Dniester River basin at the beginning of the 21st century

The relevance of the chosen topic is based on the goals and objectives of the Water Strategy of Ukraine until 2050 that provides for promotion of studies on the impact of climate change on the water content of Ukrainian rivers. The Dniester River is a transboundary river. It supplies water to Moldova and several regions of Ukraine. Predicting possible changes in the Dniester River's runoff due to global warming will help our society adapt to new climate conditions and take preventive measures. The research of the mountainous part of the watershed is of particular importance, as it is the area of runoff formation. Warming can change contribution of the snow component to the river's feed pattern and affect the total river flow. The object of the study: changes in air temperature due to global warming. The subject of the study: assessment of changes in the temperature regime within the Dniester watershed and impact of such changes on formation of its mountainous part's runoff. The study is aimed at assessing the changes in the air temperature regime within the Dniester River watershed at the beginning of the 21st century and assessing the impact of warming during winter season on formation of mountain rivers' spring floods. The main research methods include the method of difference integral curves and the method of regression analysis. The research materials include average monthly and annual air temperatures at 13 meteorological stations located within the Dniester watershed for the period of 1947-2021. The research indicated that the Dniester watershed is subject to warming. Statistically significant changes in air temperature began in 1988. Fluctuations in average annual air temperatures occur synchronously. Positive statistically significant trends over the entire observation period (1947-2021) were found for average annual air temperatures, average monthly temperatures of both warm and cold periods, and for the winter season. When considering two measurement periods (before 1989 and after), it was found that no statistically significant trends were observed before 1989. They were formed after 1989. It was also discovered that mountainous watersheds of the Ukrainian Carpathians respond to warming by forming negative trends in the fluctuations of average monthly runoff of spring floods.

Assessment of suitability of the Dniester River's water for drinking water supply

The Dniester is a transboundary river between Ukraine and the Republic of Moldova. It is the second longest river in Ukraine and the ninth in Europe. From its source to a town of Staryi Sambir, the Dniester flows through the Carpathian Mountains, then across the flat territory of Ukraine and Moldova. The Dniester Basin extends across seven regions in southwestern Ukraine (Lviv, Ivano-Frankivsk, Ternopil, Khmelnytskyi, Vinnytsia, Chernivtsi and Odesa Regions). A small area of the river in its upper reaches is located in Poland. The basin's shape is a very elongated oval that is curved in the middle, about 700 km long with an average width of 120 km. As it flows into the Black Sea, the Dniester River forms the Dniester estuary in Odesa region (between Ovidiopol and Bilhorod-Dnistrovskyi districts). The estuary area of the Dniester River is a complex landscape system at the sea-river-land contact. Drinking water is an important factor determining a person's health. Due to the intensive development of industry, agriculture and utility services, the number of pollutants that enter the environment and worsen the quality of drinking water in Ukraine keeps increasing. This increases the risk of toxic and infectious diseases spread among the population that consumes such low-quality water. That is why solving the problem of drinking water monitoring and assessment of its quality is a pressing task requiring urgent action. The article examines the quality of water for drinking needs at the water intake site of the Dniester River, a town of Biliaivka, for 2018-2022. Water quality assessment was carried out according to DSTU 4808: 2007 based on average and worst values. The methodology covers 80 indicators and, in accordance with sanitary legislation, is divided into seven separate groups (blocks). According to hygienic standards, the quality of river water is considered suitable for use if it belongs to quality classes 1-3. In this research, the analysis was carried out according to 23 indicators included in three groups, so the assessment is considered as tentative: Group I - organoleptic indicators (chromaticity, turbidity); Group II - general sanitary indicators (dry residue (mineralization), sulfates, chlorides, magnesium, alkalinity, hydrogen index, ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, phosphate phosphorus, dissolved oxygen, bichromate oxidation (COD), BSK5); Group VII – toxicological parameters (total iron, manganese, chromium (VI), zinc, petroleum products, synthetic surface active agents (surfactants), volatile phenols). It was determined that, according to the average values, the water quality of the Dniester at the water intake site is characterized as "good", which means it has clean water of acceptable quality. As for the worst indicators, the water was assessed as transitional in quality from "good" (clean) to "satisfactory" (slightly polluted).

Determination of microplastics in sediment, water, and fish across the Orange-Senqu River basin

Microplastics are increasingly recognised as posing a significant environmental threat across systems. Their pervasive presence in freshwater poses a serious concern, given the heavy reliance of both humans and biodiversity on healthy, functioning freshwater ecosystems. Acknowledgment of the potential risks led the transboundary Orange-Senqu River Commission (ORASECOM) to include sampling for microlitter (primarily microplastics) in riverine sediment, surface water, and fishes, across Southern Africa as part of the third Joint Basin Survey (JBS3) in 2021. The aim was to establish a first, basin-wide estimate of microlitter contamination across compartments, setting a baseline for further monitoring. The survey showed that the abundance of microlitter in riverine sediment (0 – 4000 particles.kg-1 dry weight (dw)) and riverine water (1.00 ± 0.71 – 69.75 ± 68.55 SD items.L-1) varied considerably between sample sites, with no correlation between the two. The abundance of microlitter in fishes was low (average of 0.7 ± 0.4 items.individual-1). Course resolution analyses suggested that microlitter concentrations in riverine sediment and riverine water at each site did not correlate with land use directly upstream, though variation in microlitter abundance did isolate some hotspots of contamination. Discharge data collected from nine gauging stations near sampling sites confirmed that low flows prevailed in the system during the study, with high flows occurring approximately 5 months prior during the summer months. There is some variation in river flow across the catchment which is a likely driver of microlitter transport. This was evident in the polymer composition for sediment and water samples. Based on the average discharge at each gauging station and microlitter concentrations measured in riverine water, the estimated microlitter load ranged from ∼889 particles.s-1 to ∼17.9 million particles.s-1, with a substantial amount ending likely up in the mudbelt adjacent to the Orange River mouth. This assessment provides a first insight into the characterisation and distribution of microlitter in multiple compartments across the Orange-Senqu River basin. Overall, the findings highlight the need for continued monitoring across compartments at catchment scales to improve our understanding of microplastic pathways into and within riverine systems.

Beyond the Border: Exploring the Complex Dynamics of Water Tensions Between India and China

This paper explores the historical context and current dynamics of the transboundary water issues between India and China. Both countries share multiple transboundary river basins, with the Brahmaputra River being one of the most significant. The importance of the Brahmaputra River to both nations goes beyond just providing resources. It has implications for national security, regional stability, and human livelihoods. However, China's upstream control over the river and its extensive dam-building projects have raised concerns in downstream India and Bangladesh about potential impacts on water availability, agriculture, and livelihoods. The river system is critical for the socioeconomic well-being of millions of people, yet the competing demands for water resources have led to geopolitical tensions. The paper highlights China's strategic use of water resources, including plans for large-scale dams, which India views as a potential threat to its water security. It also underscores the importance of a nuanced understanding of hydropolitics, emphasizing the need for human security, particularly water security, in addressing these challenges. It argues that while "water wars" are unlikely, "water tensions" are significant and must be addressed through comprehensive bilateral agreements and collaborative efforts.

Monitoring of Glacier Area Changes in the Ili River Basin during 1992–2020 Based on Google Earth Engine

The Ili River Basin, a crucial transboundary river in the arid region of Central Asia, plays a significant role in the region’s ecology and water resources. However, current methods for monitoring glacier area changes in this region face challenges in automation and accuracy due to the complex terrain and climatic conditions. This study aims to evaluate the effectiveness of the Google Earth Engine (GEE) platform for monitoring glacier area changes in the Ili River Basin from 1992 to 2020, with a focus on improving data accuracy and processing efficiency. Utilizing the Landsat data series, we employed the random forest (RF) classification algorithm within the GEE platform to extract glacier areas, optimizing a multidimensional feature set using the Jeffries–Matusita (JM) distance method, and applied visual interpretation for data refinement. Our results demonstrated that the GEE platform, combined with the RF algorithm, provided high accuracy in glacier monitoring, achieving an overall accuracy of 89% and a kappa coefficient of 0.85. During the study period, the glacier area in the Ili River Basin decreased by 184.76 km2, with an average annual retreat rate of 6.84 km2, most notably between 3800 and 4400 m in elevation. The analysis revealed that temperature changes had a more pronounced impact on glacier dynamics than precipitation. This approach significantly enhances image utilization efficiency and data processing speed, offering a reliable tool for monitoring glacier dynamics. Future research should focus on integrating additional environmental variables and extending the temporal scope to further refine glacier dynamics modeling and predictions.

Hydro-Political Dynamics Between China–India–Pakistan: Dams and Transboundary River Governance Amidst Geopolitical Contestations

Transboundary rivers raise critical concerns for state security amidst contemporary ecological strain and regional geopolitics in South Asia. The challenge of ‘water security’ is underscored by the substantial reliance on transboundary rivers, compounded by the multifaceted impacts of climate change and the simmering geopolitical tensions among riparian nations, especially in the complex dynamics between India–China and India–Pakistan. This study endeavours to illuminate distinctive characteristics of the South Asian transboundary governance framework, wherein rivers are subjected to intensive damming aimed at (a) harnessing hydroelectric potential and (b) leveraging water resources as geopolitical bargaining chips, thereby exerting pressure; however, order is not specified, particularly. In this intricate milieu, international conventions often fail to reconcile internal contradictions inherent within the transboundary governance paradigm. Consequently, transboundary water resources have metamorphosed into an extension of geopolitical realities, embodying intricate interplay between hydrology, geopolitics and state security within the region, especially between China, India and Pakistan.

Simulating streamflow in a transboundary river catchment: The implications of hybrid rainfall data

The lack of observed data for the hydrological modelling of catchments across borders has hindered the management of transboundary water resources. This study investigated the implications of different degrees of hybridization of observed rainfall data using ERA5-Land reanalysis precipitation data in simulating streamflow in the Ruvubu River catchment across the Burundi-Tanzania border. The hydrological model of the Ruvubu River catchment was set up and iteratively updated using 0%–100% hybrid rainfall data, parameterized, simulated, and then evaluated against observed streamflow data at the catchment outlet. The findings show that the performance of the hydrological model decreased as the degree of rainfall data hybridization increased. However, model parameters satisfactorily compensated for input uncertainty when the model had hybrid rainfall data not exceeding 15% hybridization. Subsequently, errors in the simulated flow were also minimal. This implies that the simulated flow from the model when it has hybrid rainfall data not exceeding 15% hybridization can represent the simulated flow when it has 0% hybrid rainfall data. These findings show the need to develop thresholds of rainfall data hybridization for different global precipitation datasets in data-scarce transboundary river catchments.

The biodiversity of fish in transboundary rivers from north-eastern Bangladesh

The biodiversity of freshwater fish is disappearing at an alarming rate around the globe, with transboundary rivers in Bangladesh being especially vulnerable. From October to December 2023, we surveyed the fish biodiversity of 11 transboundary rivers in north-eastern Bangladesh using the available literature and online FishBase data for species identification. We also added a small number of specimens from our previously examined samples that comprised of 74 fish species belonging to eight orders and twenty-four families. Our survey results indicate that the order Cypriniformes had the biggest number of species (38%), followed by the orders Siluriformes (30%), Perciformes (24%), Clupeiformes (3%), Synbranchiformes (1%), Beloniformes (1%), and Tetraodontiformes (1%). Less than 30% of the entire studied area had 26 fish, indicating that the fish population was confined to a relatively limited region. The total number of species was lower than that we had anticipated, which explains the declining trend of the fish biodiversity in the transboundary rivers of north-eastern Bangladesh. Our survey data have allowed us to gain some early understanding of the hidden biodiversity of fish in these rivers, which may prove useful to other researchers conducting follow-up studies. Since there is currently no published description of the ichthyofaunal diversity in transboundary rivers, the current data on 74 species of ichthyofauna will be useful to future researchers, planners, and policymakers. In order to safeguard the faunal composition of a riverine ecosystem, more efforts incorporating genetic data will be helpful in detecting the biodiversity of fish as well as the cryptic species of other transboundary riverine systems. These efforts will also reinforce the need to re-evaluate the checklist and promote sustainable conservation directions.

Modelling the availability of water, energy, and food resources in transboundary river basins to achieve Sustainable Development Goals 2, 6, and 7

The Water-Energy-Food Nexus (WEFN) has gained international attention as an approach for managing water more holistically, building on the progress made by the Integrated Water Resources Management (IWRM) approach. However, modelling the availability of water, energy, and food and their interconnections is complex, with major barriers that include the availability of both data and modelling platforms capable of assessing the interconnected systems of the WEFN. There have been attempts to model resource availability in each sector generally, but few attempts to consider the WEFN in complex transboundary basins, especially considering Sustainable Development Goals (SDGs). Here, a water, energy, and food availability model was developed using a combination of remotely sensed, national government reported, and global datasets. The model explores the complex interactions between the physical availability and production of water, energy, and food for several subbasins representing different states. Results showed the potential impacts of socioeconomic development, population changes and transboundary cooperation on resources. Transboundary cooperation in the case study Ma Basin in Southeast Asia, under existing resources and operations could improve monthly food security and reduce coal power operations using excess hydropower in the basin during the dry season. These findings show that transboundary cooperation improves access to energy and food, whilst potentially reducing demands for water. Furthermore, the research has highlighted ways in which transboundary cooperation can further assist in attaining SDGs 12 and 13 on responsible production and climate action, respectively. The modelling framework is easily transferable and can support similar analysis in other basins, contributing to global attainment of several SDGs.

Quantifying future water resource vulnerability in a high-mountain third pole river basin under climate change

Understanding the water resource vulnerability (WRV) in global mountain regions under climate change is crucial for water resources management and socio-economic development. However, the WRV in the high-mountain Third Pole region (with quite a few transboundary river basins) remains largely unclear. Here, we have applied a comprehensive assessment framework of WRV to a Third Pole high-mountain river basin (Nujiang-Salween River, NSR) and its dependent downstream. The framework consisted of sensitivity, exposure, adaptability, hazard, and water stress indices, considering climate change, socio-economics, government effectiveness, natural disasters, and water supply capacity of the target river basin. Our results indicate that the downstream area (with intensive human activities) often exhibited significantly higher WRV than the mountain region; while the WRV shows an M-shaped change with increasing elevation, with the highest vulnerability occurring in a relatively low elevation range (e.g., 500–1500 m for the NSR basin). In the near future, we find that the spatial pattern of WRV in the basin is alternately influenced by adaptation, water scarcity, and exposure; whereas climate change serves as the main driver affecting the WRV in the far future. These findings enhance our understanding of the WRV in high-mountain transboundary basins of the Third Pole under global change.

Anthropogenic impacts on the water chemistry of a transboundary river system in Southeast Asia

The Red River originating from Yunnan province, China is the second largest river in Vietnam in terms of length and discharge. Combination of water chemistry monitoring data of 4 years (2018–2022) from different sub-basins of the Red River (the Da, Lo, Thao, Tra Ly, and Day) with historical datasets indicates a decline in pH from 8.1 in 2000 to 7.7 in 2021, greater CO2 concentrations and a shift from waters naturally dominated by carbonate weathering to waters dominated by evaporite weathering. Such changes were most apparent in the delta area where heavy human activities have increased influxes of most dissolved chemicals, except SiO2. Evaporite weathering is particularly enhanced by mining and deforestation occurring in upstream regions of both China and Vietnam. Pyrite oxidation, alongside silicate weathering, is enhanced along the Red River Fault Zone but reduced in tributaries with a higher proportion of hydropower reservoirs. Longer water residence times in these large reservoirs (total volume > 2.7x1010 m3) located in the Da and Lo sub-basins have also increased primary productivity, leading to higher evasion/uptake of CO2 and SiO2, lower total dissolved solids (TDS), and higher pH. The total physical and chemical denudation rates of upstream mountain tributaries ranged between 0.107 ± 0.108 and 0.139 ± 0.137 mm yr−1, mainly due to reservoir implementation and instream aquatic biogeochemistry changes. Our findings demonstrate that anthropogenic activities are profound factors impacting the water chemistry of the Red River system.