Transboundary River Basins Research Articles

Assessing Flood Risk Dynamics in Data-Scarce Environments—Experiences From Combining Impact Chains With Bayesian Network Analysis in the Lower Mono River Basin, Benin

River floods are a common environmental hazard, often causing severe damages, loss of lives and livelihood impacts around the globe. The transboundary Lower Mono River Basin of Togo and Benin is no exception in this regard, as it is frequently affected by river flooding. To enable adequate decision-making in the context of flood risk management, it is crucial to understand the drivers of risk, their interconnections and how they co-produce flood risks as well as associated uncertainties. However, methodological advances to better account for these necessities in risk assessments, in data-scarce environments, are needed. Addressing the above, we developed an impact chain via desk study and expert consultation to reveal key drivers of flood risk for agricultural livelihoods and their interlinkages in the Lower Mono River Basin of Benin. Particularly, the dynamic formation of vulnerability and its interaction with hazard and exposure is highlighted. To further explore these interactions, an alpha-level Bayesian Network was created based on the impact chain and applied to an exemplary what-if scenario to simulate changes in risk if certain risk drivers change. Based on the above, this article critically evaluates the benefits and limitations of integrating the two methodological approaches to understand and simulate risk dynamics in data-scarce environments. The study finds that impact chains are a useful model approach to conceptualize interactions of risk drivers. Particularly in combination with a Bayesian Network approach, the method enables an improved understanding of how different risk drivers interact within the system and allows for dynamic simulations of what-if scenarios, for example, to support adaptation planning.

Evaluation of cooperative and non-cooperative game theoretic approaches for water allocation of transboundary rivers

Efficient water allocation in a transboundary river basin is a complex issue in water resources management. This work develops a framework for the allocation of transboundary river water between the countries located in the river basin to evaluate the characteristics of allocation approaches. The allocation of river water is obtained based on initial-water conditions, cooperative, and non-cooperative game-theoretic approaches. The initial-conditions water allocation approach assigns 34, 40, and 26% of the Harirud River flow to Afghanistan, Iran, and Turkmenistan, respectively. The game-theoretic cooperative approach assigns 36, 42, and 22% of the river flow to Afghanistan, Iran, and Turkmenistan, respectively. The non-cooperative game-theoretic approach establishes that the most stable water allocation was 42, 38, and 20% of the Harirud River flow for Afghanistan, Iran, and Turkmenistan, respectively. Human and agricultural water-stress criteria are used to evaluate the water allocations in the Harirud River basin. The criterion of human water stress has the largest influence in Iran, and the criterion of agricultural water stress has the smallest influence in Afghanistan. This work’s results indicate the initial-conditions water allocation approach favors Turkmenistan, whereas the cooperative and the non-cooperative game-theoretic approaches favors Iran and Afghanistan, respectively. The results show that the priorities of each country governs water allocation, and cooperation is shown to be necessary to achieve sustainable development.

Analysing transboundary water governance: A global‐regional‐national water governance framework of Tonle Sap Lake

AbstractTransboundary water governance is multiscale and multilevel, involving different actors with diverse powers and politics at different levels and scales. Levels and scales are key governance challenges in transboundary water governance. Although there is considerable literature on scale and level, there is very little on how to operationalize it in a transboundary river basin context. Accordingly, the present study analyses how scale and level complicate transboundary water governance, using a literature review and a case study of Tonle Sap Lake (TSL) in the Mekong River Basin to examine the level and scale affecting transboundary water governance. The present study describes the level of transboundary water governance in terms of global, regional and national implications. There are different functional spaces at each level, including agriculture, fisheries and biodiversity. Spaces are zoned into different spatial scales, based on technocratic interests, specialization, power and the politics of actors. The present study concludes that levels, spatial scales and zoning have made TSL governance more complex, leading to establishment of new institutional and legal arrangements for managing Tonle Sap, some of which compete with, conflict and overlap, meaning sound environmental management and good governance cannot be guaranteed.

Selection of Representative General Circulation Models for Climate Change Study Using Advanced Envelope-Based and Past Performance Approach on Transboundary River Basin, a Case of Upper Blue Nile Basin, Ethiopia

For the selection of global climate models in the upper basin of the Blue Nile, an advanced envelope-based approach was used. Currently, the number of general circulations models (GCM) has increased extremely. The reliability of any general circulation model in a particular region is confronted, so the selection of the appropriate climate models that can predict the climate variable is essential. Representative concentration pathways RCP4.5 and RCP8.5 were taken into account. For RCP4.5 105 GCMs were used and for RCP8.5 78 GCMs were used to select the best performance models for the Upper Blue Nile Basin for a climate change impact study. Three steps were followed to derive the best performing models in the study area based on their range of projected mean temperature and precipitation changes, the range of projected extreme changes, and the ability to reproduce past climates between 1971 and 2000 and 2071–2100. Five corners of the spectrum were used, e.g., wet-warm, wet-cold, dry-warm, dry-cold, and the 50th percentile of the temperatures. For RCP4.5 and RCP8.5, a total of 25 GCMs were chosen based on the range of anticipated mean temperature and rainfall change. Based on the range of extreme changes, 10 GCMs were chosen. Finally, for each RCP4.5 and RCP8.5, five GCMs were chosen by combining all three stages.

Nitrate sources and mixing in the Danube watershed: implications for transboundary river basin monitoring and management

Dispersed and unknown pollution sources complicate water management in large transboundary watersheds. We applied stable isotopes of water and nitrate together with contaminants of emerging concern (CECs: carbamazepine, caffeine, sulfamethoxazole, perfluorooctanoic acid and 2,4-dinitrophenol) to evaluate mixing and inputs of water and contaminants from tributaries into the mainstem of the transboundary Danube River. Stable isotope (δ18O, δ2H) variations from low values (− 13.3 ‰, − 95.1 ‰) in the Upper Danube after the Inn River confluence to high values (− 9.9 ‰, − 69.7 ‰) at the Danube River mouth revealed snowmelt dominated tributary mixing (~ 70%) in the mainstem. Stable isotopes of nitrate (δ15N-NO3) in the Danube River varied from lower values (+ 6.7 ‰) in the Upper Danube to higher values after the mixing with Morava River (+ 10.5 ‰) and showed that cold snowmelt can reduce biological activity and controls nitrate biotransformation processes in the mainstem up to 1000 km downstream. Data on emerging contaminants affirmed the low biodegradation potential of organic compounds transferred into the mainstem by tributaries. We found pollutant source tracing in large rivers is complicated by mixing of multiple sources with overlapping isotopic signatures, but additional tracers such as CECs improve the interpretation of hydrological processes (e.g., water transit time) and support tracing of nitrate pollution sources, and biogeochemical processes. Our approach can be applied to other watersheds to improve the understanding of dilution and mixing processes. Moreover, it provides directions for improving national and transboundary water quality monitoring networks.

Selection of the gridded temperature dataset for assessment of thermal bioclimatic environmental changes in Amu Darya River basin.

Assessment of the thermal bioclimatic environmental changes is important to understand ongoing climate change implications on agriculture, ecology, and human health. This is particularly important for the climatologically diverse transboundary Amy Darya River basin, a major source of water and livelihood for millions in Central Asia. However, the absence of longer period observed temperature data is a major obstacle for such analysis. This study employed a novel approach by integrating compromise programming and multicriteria group decision–making methods to evaluate the efficiency of four global gridded temperature datasets based on observation data at 44 stations. The performance of the proposed method was evaluated by comparing the results obtained using symmetrical uncertainty, a machine learning similarity assessment method. The most reliable gridded data was used to assess the spatial distribution of global warming-induced unidirectional trends in thermal bioclimatic indicators (TBI) using a modified Mann–Kendall test. Ranking of the products revealed Climate Prediction Center (CPC) temperature as most efficient in reconstruction observed temperature, followed by TerraClimate and Climate Research Unit. The ranking of the product was consistent with that obtained using SU. Assessment of TBI trends using CPC data revealed an increase in the Tmin in the coldest month over the whole basin at a rate of 0.03–0.08 °C per decade, except in the east. Besides, an increase in diurnal temperature range and isothermally increased in the east up to 0.2 °C and 0.6% per decade, respectively. The results revealed negative implications of thermal bioclimatic change on water, ecology, and public health in the eastern mountainous region and positive impacts on vegetation in the west and northwest.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00477-022-02172-8.

Diagnosing challenges and setting priorities for sustainable water resource management under climate change

Managing transboundary river basins requires balancing tradeoffs of sustainable water use and coping with climate uncertainty. We demonstrate an integrated approach to exploring these issues through the lens of a social-ecological system, combining remote and in-situ earth observations, hydrologic and climate models, and social surveys. Specifically, we examine how climate change and dam development could impact the Se Kong, Se San and Sre Pok rivers in the Mekong region. We find that climate change will lead to increased precipitation, necessitating a shift in dam operations, from maintaining low flows to reducing flood hazards. We also find that existing water governance systems in Laos, Vietnam, and Cambodia are ill-prepared to address the problem. We conclude that the solution space for addressing these complex issues will be highly constrained unless major deficiencies in transboundary water governance, strategic planning, financial capacity, information sharing, and law enforcement are remedied in the next decades.

Water-food-energy nexus for transboundary cooperation in Eastern Africa

Abstract Establishing cooperation in transboundary rivers is challenging especially with the weak or non-existent river basin institutions. A nexus-based approach is developed to explore cooperation opportunities in transboundary river basins while considering system operation and coordination under uncertain hydrologic river regimes. The proposed approach is applied to the Nile river basin with a special focus on the Grand Ethiopian Renaissance Dam (GERD), assuming two possible governance positions: with or without cooperation. A cooperation mechanism is developed to allocate additional releases from the GERD when necessary, while a unilateral position assumes that the GERD is operated to maximize hydropower generation regardless of downstream users' needs. The GERD operation modes were analysed considering operation of downstream reservoirs and varying demands in Egypt. Results show that average basin-wide hydropower generation is likely to increase by about 547 GWh/year (1%) if cooperation is adopted when compared to the unilateral position. In Sudan, hydropower generation and water supply are expected to enhance in the unilateral position and would improve further with cooperation. Furthermore, elevated low flows by the GERD are likely to improve the WFE nexus outcomes in Egypt under full cooperation governance scenario with a small reduction in GERD hydropower generation (2,000 GWh/year (19%)).

A novel approach to identifying potential hydro/political conflicts in transboundary river basins

A novel approach to identifying potential hydro/political conflicts in transboundary river basins

Impacts of future climate on the hydrology of a transboundary river basin in northeastern North America

Climate change introduces substantial uncertainty in water resources planning and management. This is particularly the case for the river systems in the high latitudes of the Northern Hemisphere that are more vulnerable to global change. The situation becomes more challenging when there is a limited hydrological understanding of the basin. In this study, we assessed the impacts of future climate on the hydrology of the Saint John River Basin (SJRB), which is an important transboundary coastal river basin in northeastern North America. We also additionally performed model benchmarking for the SJRB using four different meteorological forcing datasets. Using the best performing forcing data and model parameters, we studied the water balance of the basin. Our results show that meteorological forcing data play a pivotal role in model performance and therefore can introduce a large degree of uncertainty in hydrological modelling. The analysis of the water balance highlights that runoff and evapotranspiration account for about 99% of the total basin precipitation, with each constituting approximately 50%. The simulation of future flows projects higher winter discharges, but summer flows are estimated to decrease in the 2041–2070 and 2071–2100 periods compared to the baseline period (1991–2020). However, the evaluation of model errors indicates higher confidence in the result that future winter flows will increase, but lower confidence in the results that future summer flows will decrease.

Reconstructed precipitation in the Lohit River basin, southern Tibetan Plateau since 1720 CE and its weak linkages with monsoon‐season Brahmaputra discharge

AbstractHigh Asian glaciers and precipitation have directly or indirectly influenced the freshwater supply of billions of people and natural ecosystems in surrounding areas. To better understand the hydroclimatic changes in the High Asian transboundary river basins in the context of global warming, more precipitation‐sensitive proxy data are needed. In this paper, we used the tree‐ring cores of Pinus densata and Picea brachytyla from the southern Tibetan Plateau (TP) to establish a tree‐ring‐width composite chronology and estimate hydrological annual (September–August) precipitation (r2 = 47.0%, p < 0.01) for the Lohit River basin from 1720 to 2019. Our reconstructed precipitation was closely linked with the glacier mass balance of Shishapangma peak, which may provide us with some evidence for glacier fluctuations in the southern TP. Our precipitation reconstruction successfully captured recent dry trends and generally agreed with other tree‐ring‐based precipitation reconstructions from nearby regions. In addition, reconstructed precipitation variations were inconsistent with recorded monsoon‐season Brahmaputra discharge.

Water-sanitation-health nexus in the Indus-Ganga-Brahmaputra River Basin: need for wastewater surveillance of SARS-CoV-2 for preparedness during the future waves of pandemic

The Indus-Ganga-Brahmaputra River Basin (IGBRB) is a trans-boundary river basin flowing through four major countries in South Asia viz., India, Pakistan, Bangladesh, and Nepal. Contamination of surface water by untreated or inadequately treated wastewater has been a huge problem for pathogenic microorganisms in economies in transition. Recent studies have reported that sewage surveillance can provide prior information of the outbreak data, because faeces can contain the novel coronavirus (SARS-CoV-2) shed by infected humans. Hence, in this study we geo-spatially mapped the COVID-19 hotspots during the peak time in the first and second wave of pandemic to demonstrate the need and usefulness of wastewater surveillance strategy in IGBRB during ongoing pandemic.Further we discussed the status of sanitation, health and hand-hygiene in the IGBRB along with characterization of the challenges posed by the pandemic in achieving the United Nations Sustainable Development Goals (UN-SDGs).Monthly Geographical Information System (GIS) mapping of COVID-19 hotspots in the IGBRB showed an increase in the spread along the direct sewage discharge points. The social inequalities expose the vulnerabilities of the urban poor in terms of the burden, risks and access to Water, Sanitation, and Hygiene (WASH) needs. Such an evidence-based image of the actual SARS-CoV-2 viral load in the community along the IGBRB can provide valuable insights and recommendations to deal with the future waves of COVID-19 pandemic in this region that can go a long way in achieving the UN-SDGs.

A comparative review of decision support tools routinely used by selected transboundary River Basin Organisations

As human pressures on water resources increase, the data and decision support (DS) tools used in the governance, development and management of transboundary rivers are likely to become increasingly important. There are no universal, standardised selection processes or designs for these tools, and so it is up to individual River Basin Organisations (RBOs) to decide what to include in their capacities. This desktop study provides a broad comparative analysis of the suites of DS numerical modelling tools developed and utilised by five intergovernmental transboundary RBOs that advise their member states in the management of their shared water resources: the Permanent Okavango River Basin Water Commission; the Orange-Senqu River Commission; the Nile Basin Initiative; the Zambezi Watercourse Commission; and the Mekong River Commission. These DS tools were reviewed against the information required to enable the kinds of comprehensive assessments of proposed basin management and development plans defined in their respective agreements, which include not only hydrological parameters, but also environmental and social considerations. A review of the model development timelines showed that prior to 2000, little capacity existed in modelling of hydrological, ecosystem, and social components of the river, but that these gaps have been addressed in recent years.

Analysis of long-term strategies of riparian countries in transboundary river basins

Transboundary river basins give rise to complex water-sharing decision making that can be analyzed as a game in the sense of dynamic game theory, as done in this work. The sharing of transboundary water resources depends on the long-term shifting interactions between upstream and downstream countries, which has received limited research attention in the past. The water-sharing strategy of a riparian country depends on the strategies of other countries over time. This paper presents an evolutionary game method to analyze the long-term water-sharing strategies of countries encompassing transboundary river basins over time. The method analyzes the evolutionary strategies of riparian countries and investigates evolutionary stable strategies (ESSs) considering the payoff matrix. The evolutionary game method is applied to a river basin shared by three countries assuming two types of benefits and one type of cost to countries as decision variables of a game that reflects water use, economic and political gains, and socio-economic losses of countries. Numerical examples illustrate the strategies resulting from the evolutionary game processes and the role of several parameters on the interaction between riparian countries. The countries’ strategies are analyzed for several levels of benefits and costs, and the convergence of the strategies to a stable point is assessed. Results demonstrate the role that the upstream country’s potential benefits and the cost of conflict (i.e., non-cooperation) to other countries has on reaching a stable point in the game. This work’s results show the potential benefit to the upstream country under cooperative strategy must exceed its benefits from water use under non-cooperative strategy to gain the full stable cooperation of downstream countries. This work provides a method to resolve water-sharing strategies by countries sharing transboundary river basins and to evaluate the implications of cooperation or non-cooperation.

Water assessment in transboundary river basins: the case of the Medjerda River Basin

Water resources in the Middle East and North Africa (MENA region) face over-exploitation and over-pollution due to population growth, climate change and the lack of advanced water governance approaches. These challenges become more serious in transboundary river basins and may lead to conflict between riparian countries. The main objective of this paper is to assess water resources and needs at the Medjerda River Basin (MRB), shared by Tunisia and Algeria using the Water Evaluation and Planning (WEAP) system between 2020 and 2050. Four scenarios were built to assess the current and future status of the water supply and demands in both countries. The results show that water demands, and shortages are increasing, and some demand sites will face real water scarcity in the future due to climate change and development practices. Therefore, new allocation and management plans should be examined at the regional level based on real collaboration among all stakeholders.

Reducing Climate Change Induced Flood at the Cost of Hydropower in the Lancang‐Mekong River Basin

AbstractHydropower dams are proliferating in the riparian countries of the Lancang‐Mekong River Basin (LMRB) driven by the pursuit of renewable electricity and societal resilience to flooding. However, the tradeoffs between hydropower production and flood control are unclear in a changing environment. Here, we use a hydrological variable infiltration capacity model combined with a reservoir module to quantify the relative effects of climate change and reservoir operation on flood and hydropower generation in LMRB. Results show that while climate change would increase flood magnitude and frequency, adaptive reservoir operation can reduce flood magnitude by 5.6%–6.4% and frequency by 17.1%–18.9% at the cost of 9.8%–14.4% of basin‐wide hydropower generation. Particularly, upstream reservoirs suffer more hydropower loss (5.4 times) than downstream ones when flood control is prioritized in reservoir regulation. Our findings have implications for integrated water and energy management at the transboundary river basin under climate change.

Examining the Food-Energy-Water-Environment Nexus in Transboundary River Basins through a Human Dimension Lens: Columbia River Basin

AbstractPrevious food-energy-water-environment (FEWE) nexus studies have primarily focused on technical aspects, such as data analysis and model development. However, to inform policy and the resul...

Emergence of Water-Energy-Food Nexus Resulting from Interbasin Water Transfer: Economic Analysis for a Transboundary River Basin in South Asia

AbstractThe risk of water shortages in many regions of the world is growing with the increase of demand for water by various sectors of the economy. Interbasin water transfer (IBWT) is a technologi...

The Role of Large Dams in a Transboundary Drought Management Co-Operation Framework—Case Study of the Kabul River Basin

Hydrologic drought is a frequent phenomenon in the transboundary Kabul River Basin (KRB), the vital resource shared between the two nations of Afghanistan and Pakistan. While the KRB has vast water resources, these resources are subject to extreme hydrologic events and, as a result, are not adequately managed to deal with the stress during drought conditions in the transboundary setting with no formal agreement or treaty. Rapid population growth and increases in agricultural land will require balanced water distribution to meet the array of needs. The Soil and Water Assessment Tool (SWAT) is used to evaluate distribution options for flow frequencies under existing and proposed large dams in the headwaters of the KRB. The calibrated SWAT streamflow results are employed for statistical analyses of the Standardized Streamflow Index (SSI) and Annual Cumulative Deficit Volume (ACDV) to investigate hydrologic drought time series and identify the role of proposed dams to be used for drought mitigation. Based on the SSI, proposed dams can provide additional storage that will partially address hydrologic droughts in the future. At the same time, restrictions on agricultural land expansion and water intakes are other measures to facilitate balanced water resource availability. This study discusses the intricacies of transboundary conflict and cooperation, water rights, and drought risk management; as well, recommendations for a KRB transboundary Drought Task Force (DTF) between Afghanistan and Pakistan are provided, to develop a science-based policy for using the stored waters in large dams for drought relief, fairly and transparency.

Multimodel assessment of water budget in Indian sub-continental river basins

Estimation of the water budget is essential for water resources and environmental management. However, a reliable assessment of the water budget and water yield for the Indian sub-continental river basins has been lacking. We used 0.25° gridded meteorological observations and five hydrological models to construct water budget estimates for the Indian sub-continental river basins for the 1951–2016 period. The hydrological models (i.e. VIC, CLM, Noah-MP, H08, and CWatM) were calibrated against observed streamflow and evaluated for evapotranspiration (ET) and soil moisture. Considerable uncertainty in the water budget components (ET and total runoff) was found due to the process representation and parameterization of hydrological models. Multimodel ensemble mean of the five hydrological models performed better than individual models for most basins for water budget components. West coast, Brahmaputra, and Brahmani are the three wettest river basins. At the same time, Sabarmati, Indus, and Pennar are the three driest basins in terms of mean annual precipitation in the Indian sub-continent. The three transboundary river basins (Brahmaputra, Ganga, and Indus) have the highest water yield of 731.9 (±50.2), 582.4 (±89.4), and 231.1(±71) km3, respectively. The Budyko framework showed that only two basins (West Coast and the Brahmaputra) over the Indian sub-continent fall under the energy-limited (relatively lower atmospheric water demands) conditions. In comparison, the other sixteen river basins are in water-limited (higher atmospheric water demands) condition. Our findings have implications for water resources planning and management in one of the world's most populated regions.