Transboundary Groundwater Research Articles

Transboundary Aquifer Management Across the Americas: Hydro-Diplomacy as an Accelerator of Adaptive Groundwater Governance Amid Climate Change Challenges

The management of transboundary aquifers across the Americas faces significant challenges, especially as climate change and population growth intensify groundwater stress. Groundwater use has increased to support domestic, industrial, and agricultural demands but has been extracted through unregulated withdrawals, leading to the severe degradation of aquifer health and transboundary frictions. This study focuses on how hydro-diplomacy can accelerate the adaptive governance of shared groundwater resources in three key regions: Canada–USA, USA–Mexico, and Mexico–Guatemala–Belize. We utilized a mixed methodology by integrating a transect approach, borrowed from ecology, into the field of geopolitics. To compare the hydro-diplomatic relations and groundwater governance across a continental gradient in the Americas, we conducted a literature review and employed the TWINS conflict–cooperation matrix to evaluate governance frameworks and hydro-diplomatic interactions across time. Our findings demonstrate that hydro-diplomacy plays a pivotal role in expediting agreements, fostering transboundary data sharing, and supporting participatory governance models. In particular, the presence of supranational bodies such as the International Joint Commission (IJC) between Canada and the USA has been effective in maintaining long-term collaboration through social learning and technical cooperation. Meanwhile, in regions like Mexico–Guatemala–Belize, the absence of robust institutions has hindered progress, with limited financial and knowledge-sharing networks. This study highlights the need for improved cross-border cooperation mechanisms and the establishment of common monitoring protocols to better manage aquifer resources under the pressures of climate change. The results support the development of more adaptive transboundary groundwater management strategies aligned with Sustainable Development Goal (SDG) 6.5.2 and call for broader geopolitical cooperation to address the complexities of groundwater governance.

Perspectives and Prospects for International Water Law in the ASEAN Region: Is There an ASEAN Way to Transboundary Water Cooperation Under International Law?

Around the world there are over 300 transboundary watercourses and around 500 transboundary groundwater bodies shared by two or more States. The Association of Southeast Asian Nations (ASEAN) region contains forty-one transboundary surface and groundwater bodies shared between ten ASEAN States and the five non-ASEAN States at its periphery. As transboundary water resources they are governed under international law found in a series of layers across a spectrum of bindingness (customary international law, global–regional–multilateral–bilateral agreements and non-binding instruments). Through an analysis of the international law relevant to the governance of transboundary water resources in the region, this study seeks to explore the ASEAN approach to transboundary water governance under international law. While this analysis finds that there is no uniform practice across the region, the paper concludes with possible paths forward for the legalization of transboundary water cooperation.

Seawater intrusion assessment in the Bir Guendouz-Boulanoire coastal transboundary aquifers of Morocco and Mauritania

The Bir Guendouz region, situated in Southern Morocco, is affected by saltwater intrusion. The transboundary aquifer is shared by Morocco and Mauritania, and it serves as the primary source of freshwater in this arid region. To differentiate between freshwater and saltwater areas, 750 non-invasive vertical electrical soundings (VES) were utilized along 42 perpendiculars to the coast. Dar-Zarrouk parameters—transverse resistance (Tr), longitudinal conductance (S), and longitudinal resistivity (ρl)— were determined using VES. These techniques remove uncertainties in resistivity interpretation that may arise due to the overlap between freshwater and saline aquifers during the process of suppression and equivalence. The results indicate a significant marine intrusion in the Bir Guendouz-Boulanoire aquifer, with varying degrees of salinization observed in different zones. Freshwater zones are identified by a transverse resistance of over 4450 Ω m2, a longitudinal conductance below 41.7 mho, and a longitudinal resistivity greater than 8.7 Ω m. These characteristics can be used to prevent saltwater intrusion and ensure the sustainable use of groundwater resources. Furthermore, they will aid in improving resource management between the two nations. The study's consequences also involve safeguarding the ecosystem and ensuring the longevity of these transboundary water resources. Therefore, for researchers, professionals, and decision-makers involved in sustainable management of transboundary groundwater, this study serves as a crucial reference.

Understanding Hydrologic, Human, and Climate System Feedback Loops: Results of a Participatory Modeling Workshop

Groundwater depletion threatens global freshwater resources, necessitating urgent water management and policies to meet current and future needs. However, existing data-intensive approaches to assessments do not fully account for the complex human, climate, and water interactions within transboundary groundwater systems. Here, we present the design of and findings from a pilot participatory modeling workshop aiming to advance understanding of the hydrologic–human–climate feedback loops underpinning groundwater systems. Using participatory modeling tools and methods from the system dynamics tradition, we captured the mental models of researchers from water, social, data, and systems sciences. A total of 54 feedback loops were identified, demonstrating the potential of this methodology to adequately capture the complexity of groundwater systems. Based on the workshop outcomes, as an illustrative example, we discuss the value of participatory system modeling as a conceptualization tool, bridging perspectives across disciplinary silos. We further discuss how outcomes may inform future research on existing knowledge gaps around groundwater issues, and in doing so, advance interdisciplinary, use-inspired research for water decision-making more broadly.

At the crossroad: Stakeholders’ perspectives from Thailand and Lao PDR towards a transboundary groundwater cooperation in the Khorat Plateau aquifer

To understand stakeholder perceptions from Thailand and Lao PDR in promoting and supporting transboundary groundwater cooperation, a stakeholder workshop was conducted to look into the role of scientific information, groundwater resource use, institutional and legal frameworks and challenges and opportunities within the Khorat Platea transboundary aquifer. Results showed that (1) stakeholders perceived scientific information as pivotal in exposing potential problems and facilitate transformative change among users and policy makers across border, (2) groundwater resource use in the plateau area is limited to domestic and agricultural applications but increasing resource abstraction portrays a forbidding future scenario, (3) Thailand and Lao PDR have made significant strides in the decentralization of laws and policies pertaining to groundwater use but remains weak as local authorities lack the knowledge to manage and protect groundwater resources, and (4) Thailand and Lao PDR are at the crossroad of groundwater competition and cooperation and should work together to manage and protect the Khorat Plateau transboundary aquifer system. While anticipation for a transboundary cooperation may still need more efforts to take, interests and initiatives from all stakeholders must continue as initial elements for transboundary cooperation have already been achieved.

Assessment of groundwater vulnerability within the cross-border areas of Ukraine and Poland

Problem statement. The growing global trend of groundwater consumption and excessive groundwater abstraction in many parts of the world requires an accurate and comprehensive assessment of the potential for groundwater resource development. The EU-WATERRES international project has begun developing a concept for coordinated management and harmonized monitoring of groundwater resources in the transboundary areas of Ukraine and Poland. Studying groundwater's natural protection status or vulnerability is a priority, as groundwater pollution has become a significant environmental problem in recent decades due to the growth of industrial production and agricultural activities. Study objective is to analyze the existing materials on the natural protection of groundwater within the study area and to quantify the vulnerability of the main useful aquifer (MUA) to surface pollution in the cross-border Polish-Ukrainian area. Methodology involves the quantitative method of groundwater vulnerability assessment by calculating the time of pollutant penetration into the aquifer through the aeration zone using the modified Bindemann formula and GIS. Research results. Studies have shown that the most vulnerable among MUA there is an unconfined alluvial Quaternary horizon (alQ) of the Syan and Dniester River basins. Throughout its entire development, its vulnerability corresponds to the "very high" category because of pollution from the surface caused by precipitation filtration. The Upper Cretaceous aquifer (K2) is less vulnerable. The groundwater of this horizon in the Polish part of the cross-border area is more vulnerable - here the vulnerability corresponds to the categories "very high" and "high". In the Ukrainian part, the Upper Cretaceous aquifer is characterized by better natural hydrogeological conditions and is less vulnerable to pollution. The Lower Neogene aquifer, which has a limited distribution on the slopes of the Western Bug-Syan River watershed within Roztochia, is the least vulnerable to pollution as compared to the others. The lithological composition of the aeration zone and the thickness of weakly permeable and practically impermeable rocks have a decisive impact on the filtration time and vulnerability of groundwater to pollutants from the surface by infiltration. Scientific novelty of the research. For the first time, a quantitative assessment of the vulnerability of the MUAs for the Polish-Ukrainian cross-border area was carried out. The use of the results of this assessment will facilitate the adoption of appropriate management decisions for the comprehensive protection of transboundary groundwater, prevention of its pollution, and reduction of anthropogenic impact.

Transboundary groundwater in the Mexico-Guatemala-Belize border: opportunities for shared management using indirect methods

Transboundary groundwater in the Mexico-Guatemala-Belize border: opportunities for shared management using indirect methods

Increasing the visibility of transboundary groundwater

Increasing the visibility of transboundary groundwater

Advances in Transboundary Aquifer Assessment

This Special Issue is intended to highlight both recent work to advance the physical understanding of transboundary aquifers and factors relevant in successful collaboration on transboundary groundwater resource use. The collected papers address: (1) the identification and prioritization of the needs and strategies for sustainable groundwater development and use, along with the complexities introduced by working across borders with differing governance frameworks, institutions, cultures, and sometimes languages; (2) the characterization of the physical framework of the aquifer, stressors on the aquifer system, and how those stressors influence the availability of groundwater in terms of its quantity and quality; and (3) the incorporation of stakeholder input and prioritization directly into the process of aquifer assessment and model building. The papers provide insights into the state of knowledge regarding the physical characterization of important transboundary aquifers, primarily along the U.S.–Mexico border and the opportunities for greater stakeholder involvement in resource evaluation and prioritization. They point the way towards a future focus that combines both of these aspects of transboundary aquifer assessment for informing groundwater management discussions by policymakers.

The importance of transboundary aquifer management between Poland and Ukraine for the protection of common water

Transboundary hydrogeological units between Poland and Ukraine within the Bug and San River basins are identified, based on harmonized geological and hydrogeological data used for development of a numerical simulation of groundwater flows across the state border. This numerical model shows that the cross-border exchange of groundwater in aquifers takes place in a limited area and the flow pattern can be disturbed by the groundwater exploitation. Abstraction at current levels slightly increases the transboundary groundwater flow from Poland to Ukraine and minimally reduces the flow in the opposite direction, though not reversing the direction of water flow at the border. The simulated drawdowns do not have a transboundary range, but negative effects on surface water resources are noticeable. Estimates show that groundwater runoff to rivers decreased and infiltration losses through the riverbed increased. The quantitative status of the transboundary aquifers has not deteriorated significantly under the current exploitation but in the light of ambitious maximum allowable values for water abstraction, and in the absence of joint resource management, this problem will arise in the near future. Joint management should focus on a broader legal consensus, improvement of institutional relations, and integration of monitoring and groundwater status assessment systems.

METHOD OF ESTIMATING JOINT USE OF GROUNDWATER IN TRANSBOUNDARY AQUIFERS ON MATHEMATICAL MODELS

The methodological approach to solving the problems of optimal sharing of transboundary groundwater is determined as a result of mathematical modelling. Differential equation reproduces the confined-unconfined filtration of groundwater in the multi-stratified system as the basic approximation. Must be considered a single flow of underground waters, whose existence and properties depend on the areas of supply and discharge, which may be located in the territories of different countries. For regulation of transboundary water use the following criteria are suggested: quantitative estimation of ground and surface water depletion due to long time water discharge, calculation of extending time from contamination sources, identification of unknown location a possible source of contamination by groundwater flow velocity inversion. As an example, the results of modelling of cross-border flows underground in the territories Russia-Ukraine and Russia-Kazakhstan are given. The hydrodynamic math models have to be a subsystem of the total monitoring. Using such approach, both geological service and government authorities meet the real instrument for assessing and forecasting conditions of underground hydrosphere and efficient regulating of the anthropogenic load.

Possibilities of Using the Unitization Model in the Development of Transboundary Groundwater Deposits

Groundwater belongs to the category of strategic minerals, along with hydrocarbon resources, so the supply of drinking water will become one of the urgent problems of modern society. The management of groundwater resources and their protection is a very complicated task, especially in border areas where neighboring states jointly exploit aquifers. The problem of transboundary water resources management, in particular groundwater, has been considered at the international level for more than 30 years. However, despite the adoption of a number of conventions, agreements and programs, both at the global and in the format of interstate relations, an understanding for the approach of a universal solution to the transboundary water issue has not yet been formed. An attempt to study the possibilities of applying the principles of unitization on the example of transboundary oil and gas fields in comparison with groundwater cross-border deposits is made in the paper for the first time. As a successful example, the unitization agreement between Norway and the UK for the development of the Frigg field was chosen. It is established that unitization agreements concluded by states in the joint development of transboundary mineral deposits, actively used in regulating the activities of transboundary oil and gas fields, can be used as one of the possible models of international agreements on the extraction of groundwater in transboundary territories.

Numerical Modeling of Transboundary Groundwater Flow in the Bug and San Catchment Areas for Integrated Water Resource Management (Poland–Ukraine)

On the Polish–Ukrainian borderlands, there is the Lublin–Lviv transboundary groundwater aquifer system, which is of key importance in shaping strategic groundwater resources. Due to the particular importance of this aquifer system, the two neighboring countries are obliged to undertake joint actions to protect it. The integrated management of the Lublin–Lviv aquifer system seems difficult due to the significant spatial and temporal scale of groundwater flows in the region. To support internationally integrated management, a transboundary geological model was developed. Based on this model, a hydrogeological conceptual model has been developed, which allowed for a numerical model of groundwater flow to be calculated. The model research helped diagnose potential problems by determining the scope of the area with cross-border flows and quantifying the flows between Poland and Ukraine. In addition, the numerical model was used to define the optimal cross-border management unit and the conditions needed to sustainably exploit the Lublin–Lviv aquifer system. Basing on the research results it was concluded that groundwater flows in transboundary aquifers very on a regional scale and that the range of areas of importance for transboundary groundwater flows is much smaller than the pre-selected partial catchments of the Bug and San Rivers. The results of this study may significantly contribute to the preparation of joint water management plans.

Why do we need to care about transboundary aquifers and how do we solve their issues?

As the reliance on transboundary groundwater is increasing globally, it is important to understand and address the specific issues raised by the assessment and management of transboundary aquifers (TBAs). Building on 20 years of TBA experience and through a three-pillar framework (assessment, cooperation-collaboration, shared management), the key elements to addressing TBA issues are described, including a multidisciplinary approach, identification of hotspot zones, local vs border-wide approaches, appropriate funding models, and an increased recognition of the role and value of each TBA.

Groundwater governance in international river basins – An analysis of the Norwegian-Swedish transborder area

Study regionScandinavia, Norway and Sweden. Study focusTransborder cooperation and knowledge of transboundary aquifers (TBAs) has evolved through an inventory under the convention on the protection and use of transboundary watercourses and international lakes (Water Convention) from 1992. Within EU countries, the Water Framework Directive (WFD) from 2000 intends to contribute to achieve the objectives of the Water Convention. This study analyses the national groundwater management systems in Norway and Sweden and their implementation of the WFD. Emphasis has been placed on international river basin districts (IRBD) and transborder cooperation. The findings offer recommendations for authorities and policy-makers on how they could improve the long-term management and ensuring transparent decision-making of transboundary groundwater management. New hydrological insights for the regionIn Norway and Sweden, TBAs play a minor role in supplying freshwater resources and sustaining socio-economic development in transborder areas. The analysis shows that surface water overrules ‘the invisible’ groundwater. This study highlights several factors that need to be addressed. First, the Norwegian national water management systems are fragmented and over-complex, which complicates national and transnational cooperation. Second, Swedish legislation must be revised to meet the requirements of the WFD regarding IRBD delineation. Finally, transborder dialogue and joint projects on groundwater mapping are necessary for mobilising resources and the necessary political support to obtain knowledge on TBAs.

Numerical Modeling of Transboundary Groundwater flow in the Bug and San Catchment Areas for Integrated Water Resource Management (Poland–Ukraine)

Numerical Modeling of Transboundary Groundwater flow in the Bug and San Catchment Areas for Integrated Water Resource Management (Poland–Ukraine)

Management of groundwater resources in transboundary territories (on the example of the Russian Federation and the Republic of Estonia)

Groundwater, as a source of water supply, the most important mineral and geopolitical resource, , is often the only source of high-quality drinking water that is protected from pollution under conditions of increasing deterioration of surface water quality. Transboundary groundwaters are the focus of hydrogeological researchers for a number of reasons, including the reduction and pollution of water resources as a result of economic activities. The increased controversy between states over transboundary water issues has necessitated the development of international legal documents on issues related to water conflict prevention and the sustainable use of fresh water. As part of the analysis of the problem of legal regulation of groundwater extraction from transboundary aquifers and complexes, it is proposed to consider this aspect on the example of Russia. The problems of regulation of rational use and protection of fresh water in the bilateral treaties of the Russian Federation were revealed; a methodology for the management of groundwater extraction in the territory of the transboundary aquifer was developed, the size, parameters, and factors influencing the formation of the transboundary zone have been determined (based on research and analysis of water intake activities in the border areas of the Russian Federation and the Republic of Estonia) were determined.

Sustainable Management of Transboundary Groundwater Resources: Past and Future

Groundwater resources at all times have provided and continue to provide a significant impact on the economic, social, and often political activities of any state, especially if the reserves of this strategic resource are limited. Coordinated groundwater resources management is one of the main conditions for the sustainable development of countries’ transboundary basins, affecting all aspects of human activity, including water supply, agriculture, industry, hydropower, water transport, environment, and the very quality of human life. Modern international trends in the field of transboundary groundwater resources management is undergoing significant changes. This article dwells upon the features of groundwater as a mineral, the structure of state groundwater management in the Russian Federation, the regulation of transboundary groundwater use, and protection at the international and domestic levels are analyzed. The system of management of the transboundary aquifers of Kazakhstan and Belarus is considered in more detail. The unitization approach used for coordinated development of oil and gas fields can, to some extent, serve as a model for managing common groundwater aquifers located on the border of neighboring states. Dogmatic and comparative legal methods consisting of analyzing the applicable legal regulations on the use and protection of groundwater were used. Several recommendations for improving the system of state sustainable management of groundwater resources at the global level are proposed.

Modern Trends in the Field of Solving Transboundary Problems in Groundwater Extraction

The intensive exploitation of water resources negatively affects the ecological situation in many international water objects. The problem of a shortage of drinking water is aggravating, water bodies are subject to pollution by domestic and industrial wastewater, and the water quality in the basins of international water courses continues to deteriorate. This situation primarily requires legal regulation. Until recently, despite a significant number of existing international treaties on the use of transboundary waters, there was no universal international legal act to systematize the basic principles and norms of behavior of the states in this area. The most important direction for improving public administration in the field of use and protection of transboundary groundwater bodies is the development and expansion of international cooperation and the legal consolidation of the rights and obligations of states through the adoption of legislative acts on various levels. Modern international policy in the field of transboundary groundwater resources management is undergoing significant changes. The very concept of a transboundary territory in relation to groundwater extraction was adopted both in Russia and in Europe in the early 2000s. However, the main criteria for the definition of a transboundary territory have not yet been formulated anywhere. This gives rise to the need to define a transboundary aquifer in international legislation, as well as to limit the size of this aquifer. This paper is devoted to the analysis of approaches to the definition of “transboundary aquifer”, emerging problems in this area, the legal framework, and conflicts in the field of transboundary regulation of groundwater. The zone of responsibility in groundwater extraction at the transboundary territory of neighboring states is defined.

The Lake Chad transboundary aquifer. Estimation of groundwater fluxes through international borders from regional numerical modeling

Study RegionAfrica. The Lake Chad transboundary aquifer Study FocusTo understand transboundary groundwater hydrodynamics and estimate quantitative groundwater fluxes values between aquifer-sharing countries. To enable estimations, we developed an updated 3D ‘quasi steady-state’ regional groundwater flow model of the Chad Formation based on integrating extensive available information and reflecting the best current conceptual understanding to date. The conceptual model was tentatively assessed by a steady-state numerical model based on MODFLOW. New Hydrological Insights for the RegionThis model simulates lateral groundwater flows between neighboring countries, and also provides insights into the large-scale flow pattern and flows among hydroestratigraphic units. Modeling indicated that groundwater fluxes through international borders exist between Basin-sharing countries, except between Central African Republic and Cameroon, where a buffer area was considered for modeling purposes, leading to more uncertain results. From 14ºN parallel to further north, data are scanty and outcomes should be carefully considered. Forecasting transboundary impacts indicated that changes in recharge rates were more sensitive that changes in groundwater abstraction. To date, abstraction represents a small part of the water balance, but if it increases, it can become a driving factor in the future. Land use change and water use in the source areas (southern area) will have the strongest impact on transboundary groundwater flows due to changes in recharge, which will lead to quantitative changes in groundwater levels, artesian conditions, or even water quality.