Transboundary Basins Research Articles

Use of the SWAT Model to Simulate the Hydrological Response to LULC in a Binational Basin between Ecuador and Peru

Land use change has played a crucial role in altering the hydrological behavior, making detailed assessments essential to ensure sustainable water resource management and the conservation of natural ecosystems. This study focuses on simulating the impact of different Land Use and Land Cover (LULC) scenarios for the years 1985, 1995, 2005, and 2015 on the water balance in the Puyango-Tumbes River basin, which spans across Ecuador and Peru, during the period 1981-2015. The results indicated an 18.3% increase in the grassland areas and a significant 38.2% reduction in the savanna zones, contributing to an annual 2.1% increase in the Evapotranspiration (PET) rates. These land use changes led to a 29.2% decrease in the Percolation (PERC), a 20.7% decrease in the Surface Runoff (SURQ), a 33% reduction in the Groundwater Flow (GW_Q), and a 26.6% decrease in the Annual Water Yield (WYLD), as well as a slight reduction of 0.9% in the Lateral flow (LAT_Q). These findings highlight the importance of considering land use changes to ascertain the sustainable management of natural resources, particularly in a transboundary basin.

Hydrochemical and Isotopic Characterization of Groundwater in the Nakivale Sub-Catchment of the Transboundary Lake Victoria Basin, Uganda

This study characterized groundwater resources for the Nakivale sub-catchment of the transboundary Victoria Basin in Uganda using classical hydrochemical and stable isotopic approaches. Groundwater in the study area is essential for domestic, agricultural, and industrial uses. As a sub-domain of the larger Victoria Basin, it also plays a crucial role in shaping the hydrological characteristics of this vital transboundary basin, both in terms of quality and quantity fronts. This makes its sustainable management and development vital. The predominant groundwater type is Ca-SO4, with other types including Ca-HCO3, Na-Cl, Na-HCO3, and Ca-Mg-SO4-Cl. Hydrochemical facies analysis highlights the importance of rock–water interactions in controlling groundwater chemistry, mainly through incongruent chemical weathering of Ca-rich plagioclase feldspars and the oxidation of sulfide minerals, such as pyrite, which are prevalent in the study area. Groundwater recharge is primarily influenced by the area’s topography, with recharge zones characterized by lineament networks, located in elevated areas. Stable isotope analyses indicate that groundwater mainly originates from local precipitation, while tritium data suggest the presence of both recent and older groundwater (likely over 20 years old). The study’s comprehensive approach and findings contribute significantly to the understanding of groundwater systems in the region, thus providing valuable insights for policymakers and stakeholders involved in water resource management and development strategies.

The relationship between land use change and flood flows, a case study in a transboundary watershed

Introduction: Introduction: The HEC-HMS model was applied in the transboundary basin of the Zarumilla River (Ecuador – Peru) to simulate the flows that would occur during maximum precipitation events. Methodology: The model integrated the precipitation determined by intensity equations, the infiltration defined by the curve number, the rain - runoff transformation by unit hydrographs, the hydrological routing calculated by applying Muskingum - Cunge and was calibrated by a frequency analysis using the hydrometric information available. Results: The model was executed satisfactorily and the resulting maximum flows at the outlet of the basin varied between 1.100 m3/s and 1.670 m3/s depending on the return period. A land use scenario for the year 2027 was generated using information from 2014 and 2017 that was evaluated with the model. Discussion: The transitions with the largest area of influence observed were pasture to crop, forest to crop and crop to pasture. Other classifications do not present a significant change. Conclusions: The flows calculated with the coverage of the generated scenario are lower than those calculated for 2017, due to the expansion of crops, which are mostly fruit crops. Despite this, the variation in flow rates was not very significant.

Water as an argument for peace and cooperation in transboundary basins

Water as an argument for peace and cooperation in transboundary basins

Drivers of Widespread Floods in Indian River Basins

Abstract Widespread floods affecting multiple subbasins in a river basin have implications for infrastructure, agriculture, environment, and groundwater recharge. However, the crucial linkage between widespread floods and their drivers remains unexplored for Indian subcontinental river basins. Here, we examine the occurrence and drivers of widespread flooding in seven Indian subcontinental river basins during the observed climate (1959–2020). The peninsular river basins have a high probability of widespread flooding, compared to the transboundary basins of the Ganga and Brahmaputra. Favorable antecedent baseflow and soil moisture conditions, uniform precipitation distribution, and precipitation seasonality determine the probability of widespread floods in Indian river basins. The widespread floods are associated with large atmospheric circulations that cause precipitation in a large part of a river basin. Our findings highlight the prominent drivers and mechanisms of widespread floods with implications for flood mitigation in India.

State of continental discharge estimation and modelling: challenges and opportunities for Africa

ABSTRACT Africa’s diverse climates and sparse hydro-meteorological networks create significant challenges in accurately estimating river discharge. Discharge data are crucial for managing water resources and predicting extremes. Our review assesses the data gap, existing methods, and technologies for river discharge estimation in Africa. Limited gauging networks on rivers, including in 63 transboundary basins, hinder accurate discharge modelling, affecting resource management and disaster response. Despite the potential of remote sensing, Geographic Information System (GIS), satellite imagery, and machine learning, their large-scale application for river discharge monitoring in Africa is limited. We propose the use of a monitoring system involving local communities in data collection and decision making, supported by global data centres, enhanced regional data sharing, and strengthened transboundary cooperation. For example, incorporating water data products, including discharge data, in data cubes, such as Digital Earth Africa, could improve monitoring. Strategic investments in hydro-meteorological instrumentation are crucial for strengthening climate resilience.

The role of third parties in shaping transboundary cooperation of the Sixaola river basin (Costa Rica and Panama): an analysis through States’ involvement, technocratic turn, and reterritorialization

Transboundary water management in the Sixaola basin, shared by Costa Rica and Panama, has historically involved significant contributions from thrid - third and not thrid - parties. This study investigates their evolving roles and the implications for governance in this context. We conducted a comprehensive analysis of non-State actors interventions over time, focusing on changes in strategies, priorities, and their impact on transboundary basin governance. Our findings indicate that while non-state actor initiatives have attracted attention and financial resources, they have also introduced significant governance challenges, leading to inconsistencies in basin development. The analysis reveals that limited governmental involvement and the technocratic turn in development strategies have raised questions about basin development and its tangible impacts. Additionally, reterritorialization efforts highlight a local tendency to better align existing functional spaces with local concerns. This study contributes to the literature on transboundary basin management by providing insights into the multifaceted role of non-state actors in the Sixaola basin. It explores a case where governments remain distant in defining governance systems, highlighting the added value of focusing on non-state actors to grasp the complexity of hydropolitics and discussing the politics of river basin development.

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.

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.

Hydroecological limitations of the use of water resources of transboundary rivers of the steppe zone (through the example of the Ural and Tobol Rivers, Russia)

To identify the main types of hydroecological restriction on the use of water resources and their spatial patterns in the Ural and Tobol river basins within the steppe zone.A comprehensive assessment of the water‐environmental situation in the regions of the studied basins studied was carried out on the basis of the calculation of water‐environmental stress – the ratio of water intake and free flow (average long‐term flow minus ecological). To assess the environmental restrictions on water use, data from the State reports, “On the State and Protection of the Environment" were used. Exposure to the risk of flooding of settlements was analysed according to information from the registers of settlements at risk of flooding (flooding). Analysis of the dynamics of channel processes was carried out using Landsat satellite images. For the rivers of the Tobol River basin, an approach based on taking into account the nature of channel transformations in the sectors of the state border of the Russian Federation and the Republic of Kazakhstan was used.As a result of the research, the main types of hydroecological restriction in the transboundary basins of the Ural and Tobol were identified. In particular, the key factor limiting water use is the availability of a guaranteed volume and adequate quality of water resources. Hydrological restrictions associated with the negative impact of water include the risks of flooding of settlements during the passage of spring or summer floods, as well as intensive riverbed transformations (in the Ural River basin).The Ural and Tobol river basins (within the steppe zone) are characterised by the development of a rather complex hydroecological situation in some areas. Taking into account the long cycle of low water content in these rivers, the general hydroecological situation has aggravated in recent decades, the primary problem being that of guaranteed provision of water resources of standard quality. As a result, an urgent task is to develop an algorithm for a comprehensive assessment of hydroecological restrictions on water use and their consequences for the population and economy of the regions of the steppe zone.

Three-dimensional model and environmental fragility in the Guarani Aquifer system, SE-Brazil

The Guarani Aquifer System (GAS) is a vast transboundary continental sedimentary basin in southern South America, encompassing sedimentary rocks and basalt flows across Uruguay, Paraguay, Argentina, and Brazil. It serves as a crucial water resource for urban supply and irrigation. This study aims to propose geophysical, geometric, and fragility models of the GAS in a critical exploitation area, utilizing geological data, geophysical logs, geomorphometry, and information from tubular wells. The models define distinct geophysical ranges for each formation and identify contacts between sedimentary and basaltic rocks. Integration of horizontal and vertical spatial distributions of geophysical and geological data forms a 3D model, revealing basaltic flows and intrusions distribution in fragile areas between formations, and potentially connecting aquifer layers. Natural fragility zones, characterized by high fracture densities, are observed in the central-east region, while outcrop and recharge areas of the main aquifer hydrofacies are found in the north. The 3D model highlights similarities between the topography of the Botucatu Formation (KJb – eolian sandstones) and the potentiometry of GAS at local scales, and overexploitation zones in Ribeirão Preto's city center. The assessment prioritizes areas at risk and conservation strategies for sedimentary aquifers, emphasizing interactions between surface and groundwater and addressing issues of overexploitation, identifying high-impact risks on GAS hydrodynamics and water quality.

Exploring the Spatial Distribution of Coastal Drainage Basins in Turkey

Coastal regions are vital areas globally, serving as hubs for human habitation and economic activities. Water, being the fundamental resource for life, plays a crucial role in sustaining ecosystems and shaping coastal landscapes. The convergence of river systems in coastal zones underscores their significance in the hydrological cycle and aquatic biodiversity. However, managing these valuable yet vulnerable regions presents multifaceted challenges, necessitating robust management frameworks supported by monitoring and assessment tools. In Türkiye, a country with limited freshwater resources, the management of coastal zones is particularly complex due to increasing pressure on resources and land. This study examines the distribution and characteristics of river and coastal basins in Türkiye. Through spatial analyses on Geographical Information System and basin delineations with watershed modelling program, the study clarifies the regional differences and obstacles encountered by coastal provinces spanning the entirety of Türkiye's coastal borders. The results offer valuable understanding regarding the spatial dynamics of Türkiye's coastal areas with particular emphasis on the significance of Black Sea coastal basins and all coastal provinces. Firstly, river basin systems draining into the Black Sea constitute the majority of Türkiye's surface area. Although the Black Sea region covers only 14% of the total area, more than half of the country's surface area, excluding transboundary and endorheic basins, drains into the Black Sea. Similarly, the analysis of basin types reveals that coastal basins constitute approximately 18% of the drainage areas associated with our coastal waters, nearly one-fifth. This distinction between coastal basin and river basin boundaries differs from the traditional zoning approach in river basin management and coastal area management plans in Türkiye. Consequently, it is anticipated that this spatial evaluation, which has brought a new perspective, will significantly contribute to addressing management challenges, especially the studies that will be evaluated together with population and resource use.

New thinking in the theoretical framework of hydro-hegemony, with emphasis on the aras transboundary basin

New thinking in the theoretical framework of hydro-hegemony, with emphasis on the aras transboundary basin

Evaluation of Near Real-Time Global Precipitation Measurement (GPM) Precipitation Products for Hydrological Modelling and Flood Inundation Mapping of Sparsely Gauged Large Transboundary Basins—A Case Study of the Brahmaputra Basin

Limited availability of hydrometeorological data and lack of data sharing practices have added to the challenge of hydrological modelling of large and transboundary catchments. This research evaluates the suitability of latest near real-time global precipitation measurement (GPM)-era satellite precipitation products (SPPs), IMERG-Early, IMERG-Late and GSMaP-NRT, for hydrological and hydrodynamic modelling of the Brahmaputra Basin. The HEC-HMS modelling system was used for the hydrological modelling of the Brahmaputra Basin, using IMERG-Early, IMERG-Late, and GSMaP-NRT. The findings showed good results using GPM SPPs for hydrological modelling of large basins like Brahmaputra, with Nash–Sutcliffe efficiency (NSE) and R2 values in the range of 0.75–0.85, and root mean square error (RMSE) between 7000 and 9000 m3 s−1, and the average discharge was 20611 m3 s−1. Output of the GPM-based hydrological models was then used as input to a 1D hydrodynamic model to assess suitability for flood inundation mapping of the Brahmaputra River. Simulated flood extents were compared with Landsat satellite-captured images of flood extents. In critical areas along the river, the probability of detection (POD) and critical success index (CSI) values were above 0.70 with all the SPPs used in this study. The accuracy of the models was found to increase when simulated using SPPs corrected with ground-based precipitation datasets. It was also found that IMERG-Late performed better than the other two precipitation products as far as hydrological modelling was concerned. However, for flood inundation mapping, all of the three selected products showed equally good results. The conclusion is reached that for sparsely gauged large basins, particularly for trans-boundary ones, GPM-era SPPs can be used for discharge simulation and flood inundation mapping.

Surface Water Resources Planning in an Ungauged Transboundary Basin Using Satellite Products and the AHP Method

Global concern over optimizing transboundary water resources for residents is hindered by the lack of observational data, particularly in ungauged basins, mainly due to inaccessibility or security issues. Remote sensing and GIS technology provide a practical solution for monitoring and managing water resources in such basins. This research evaluates surface water resources in the Qaretikan ungauged transboundary basin using satellite products for precipitation, temperature, and evapotranspiration from 2005 to 2014. The accuracy of these datasets was assessed using statistical measures. The water balance components, i.e., precipitation and evaporation, were utilized to calculate runoff over the basin using the Justin method. Downstream environmental flow was estimated using the Lyon method, and available water was determined. This study identified a potential annual storage water of 11.8 MCM in the Qaretikan basin. The Analytic Hierarchy Process (AHP) integrated expert opinions to prioritize water usage decisions based on proposed decision options. The results revealed greenhouse cultivation water allocation as the top priority among the identified options, highlighting its importance in sustainable water resource management within the basin.

Delineation of a conceptual groundwater flow model of the Kandi basin in Benin (West Africa): Insights from isotopes, piezometric and hydrological investigations

Study regionThe hydrogeological Kandi basin, the Benin’s sector of the transboundary Iullumeden basin, located in northern Benin, West Africa Study focusIn many parts of the world, groundwater resources constitute the main, if not the only, source of potable water available to address a growing demand for numerous uses. And yet, a basic understanding of the hydrogeology of many critical groundwater systems is lacking in many instances. Only when severe groundwater depletion or serious groundwater quality issues arise is the attention paid to the lack of specific groundwater studies. This study targets the Kandi basin, a ∼8700 km2 hydrogeological basin located in northern Benin, which is the primary source of potable water for its inhabitants, but its hydrogeological functioning remains unclear. We conducted isotopic and hydrogeological investigations in this basin from 2013 to 2019 to characterize groundwater recharge processes and delineate flow patterns. The resulting hydrological and geochemical data have been integrated and interpreted using tools including mapping tools. New hydrological insights for the regionThis study has identified the preferential groundwater recharge areas and characterized the main groundwater flow paths. Predominant areas of groundwater dischage into surface water, regardless of the seasons, were detected and areas where the surface-groundwater interflows are season-dependent were discriminated. The main findings presented in this paper are expected to provide a baseline for further in-depth hydrogeological investigations, namely groundwater flow modeling that will help understand the impacts of various groundwater withdrawals and climate changes on the groundwater resources availability of this basin.

Water Banking as a Strategy for the Management and Conservation of a Critical Resource: A Case Study from Tunisia’s Medjerda River Basin (MRB)

The increasingly adverse impacts of climate change (e.g., rainfall patterns, droughts, and floods), coupled with the ever-increasing water demands, are often translated into a contingent liability for water users’ communities. Additional complexities arise due to competing priorities, water rights, and transboundary water sources. Therefore, conventional water management practices should shift toward more comprehensive and responsive integrative approaches, even for systems with limited data. Furthermore, water managers must prioritize dynamic and interactive management techniques for existing systems. One such management technique is water banking, which is the focus of this study. Herein, a dynamic interactive water allocation model, which encompasses the water managers and heterogeneous parties with competing demands, is developed. The voluntary sales of water shares between parties are illustrated through the specific case of the Medjerda River in Tunisia, an excellent example of a transboundary basin with limited hydrologic data and conflicting water use requirements between its upstream and downstream sectors. A set of scenarios is developed for the first analysis with this model: two management scenarios that include the no-water trade and the water banking option; three demand scenarios that include a combination of steady-, low-, and high-water demand conditions; and two hydrologic scenarios that include dry and wet conditions. Based on an economic model, the economic impacts of water banking are calculated using estimates of the costs of water shortages brought to users that illustrate the magnitude. The results show that the water banking technique can improve water resource availability by optimizing the management, operation, and conservation of natural and artificial water storage systems and water distribution infrastructure. Specifically, water banking can offset users’ profit losses during severe conditions (i.e., drought), even with limited hydrologic data. This water management technique would allow the Tunisian government to minimize the economic impacts on farmers from drought and to plan for future uncertainties by optimizing the water storage potential in years of abundant rainfall.

Lessons from the last 30 years for future water resource management in national and transboundary basins

Lessons from the last 30 years for future water resource management in national and transboundary basins

Transboundary water resource management and sustainable development in the lancang-mekong river basin: an analysis of international water law

ABSTRACT The Lancang-Mekong River Basin stands as one of the most critical and complex transboundary basins globally, where the utilization and protection of water resources are paramount. This basin, linking China, Myanmar, Laos, Cambodia, Thailand, and Vietnam, is characterized by a dense population and rapid industrial and agricultural development, fostering frequent economic and cultural exchanges. Cooperative efforts in water resource utilization and protection among these countries lead to issues such as resource disputes, environmental pollution, and collaboration barriers. Since the six basin countries have not jointly joined any international convention on water resources development or protection, disputes have been resolved and cooperation promoted through existing inter-state cooperation mechanisms for many years. However, these mechanisms often fall short due to the lack of common guiding principles. Achieving sustainable water resource development in the Lancang-Mekong River Basin aligns with the national interests of the six countries. The basin states can establish a transboundary Environmental Impact Assessment system and a dispute settlement mechanism. Constructing a comprehensive Integrated Water Resource Management Cooperation Mechanism, rooted in the fundamental principles of international water law, is crucial for enhancing the level of international cooperation within the basin.