Hydrogeological Characterization Research Articles

Hydraulic impact of pressure transients from water conveyance tunnel on the complex hydrogeological system: A case study HPP Pirot, Serbia

Hydraulic tunnels, integral components of hydropower plant (HPP) systems, traversing diverse rock masses, pose challenges for long-term operation. The study’s main goal was to investigate how hydraulic transients originating from the headrace tunnel transfer through the concrete lining and manifest in surrounding aquifer systems. In this experimental study at the water pressure tunnel of HPP Pirot (Serbia), a novel monitoring approach was employed. The internal piezometers with highly sensitive probes are distributed strategically along the tunnel in different geological environments. This approach involved monitoring of water pressure in the surrounding rock masses and observing the impact of hydraulic transients generated by HPP operation. A comprehensive analysis of monitoring data, incorporating ordinal and partial correlations and considering geological features, provides a profound understanding of groundwater dynamics, pressure transient phenomena, and hydrogeological characterization during HPP operation. The study highlights the complex and spatially diverse hydrogeological environment, emphasizing the varying reactivity of pore pressure during HPP operation, particularly concerning Water Mass Oscillations (WMO). Reactive piezometers near the surge tank demonstrate significant pressure variations, while those located further away display synchronous pressure changes with reduced amplitudes. Schematic hydrogeological models have been created based on the hydraulic impacts of HPPs in different geological environments along the tunnel route. The water pressure response enabled aquifer characterization of (1) a thin-layered, low-fissured aquifer closely related to the reservoir, with low influence on WMO transients; (2) a low-fissured, compartment aquifer or non-aquifer with minimal to no influence on WMO transients; (3) a well-structured karst aquifer system influenced by WMO transients; (4) a fault-controlled zone of deep hypogene karst aquifer discharge highly influenced by WMO transients; and (5) an aquifer with a dominant development of the karst conduit system highly influenced by WMO transients. The study highlights the significance of monitoring water pressure within the rock mass as a fundamental element in analyzing the interaction between water pressure tunnels and the hydrogeological environment. Applying the presented instrumentation and methodology facilitates effective monitoring in research areas where pressure tunnels are constructed.

An approach for the design of dewatering systems: the case of an excavation for the construction of the assembly shaft of a tunnel boring machine

Robust approaches are needed for designing efficient dewatering systems of deep excavations below the water table to avoid unforeseen incidents (e.g., bottom instabilities in deep excavations and flooding, among others). This paper proposes a methodology, which integrates existing experiences, that was adopted to design the dewatering system of an excavation in the city of Barcelona (Spain). The approach consists of combining: (i) detailed geological and hydrogeological characterizations, (ii) numerical modelling for parameter estimation and drawdown predictions, and (iii) analytical assessment for stability evaluation and soil deformation predictions. The idea is that by combining a set of relatively easy to apply methods, it is possible to successfully solve a complex and risky problem. The methodology allows designing efficient dewatering systems, increasing safety and mitigating potential impacts of groundwater pumping. The most significant conclusion is that the most important step of the proposed approach is the hydrogeological characterization because it allows building realistic and representative numerical models to address most of the challenges associated to dewatering.

Hydrogeological characterization of low permeability medium for conceptualization of a mine site in Eastern Turkey

The mining site in Eastern Anatolia of Turkey were encounter a significant risk of slope instability within the operational area. One of the processes that govern slope stability is the pore water pressure distribution. The conceptualization and characterization of porous media serve as fundamental prerequisites for the implementation of numerical methods aimed at predicting pore water distribution. This study aims to characterize the hydrogeological properties of water bearing rocks in the active mining site in Eastern Anatolia of Turkey. A total of 21 wells and drill holes were drilled in the study area to conduct in-situ tests, monitoring, and sampling. The large diameter wells drilled in surrounding the carbonate rocks were to determine the groundwater flow and boundary conditions and also wells tapped metasediments and diorite unit for hydraulic testing. The lugeon tests and installation of vibrating wire piezometers were carried out at small diameter drill holes to obtain localized hydraulic conductivity of metasediments and diorite at different depths and monitoring pore water pressure distribution along some critical cross-sections. The results obtained from these tests are used for developing hydrogeological conceptual model for groundwater flow. The results of in-situ tests show that the metasediment and diorite units act as a single hydrostratigraphic unit. The metasediments and diorite have high total porosity and low specific yield indicating that the pore water is retained by electrostatic forces in the medium and it resists flow due to low hydraulic conductivity. The vertical variation in hydraulic conductivity values indicates that the medium is highly heterogeneous.

Contribution of vertical electric sounding, Landsat 8 and SRTM images to hydrogeological characterization: case study of Batié, West-Cameroon

Contribution of vertical electric sounding, Landsat 8 and SRTM images to hydrogeological characterization: case study of Batié, West-Cameroon

Contribution to advancing aquifer geometric mapping using machine learning and deep learning techniques: a case study of the AL Haouz-Mejjate aquifer, Marrakech, Morocco

Groundwater resources in Morocco often face sustainability challenges due to increased exploitation and climate change. Specifically, the Al-Haouz-Mejjate groundwater in the Marrakesh region is faced with overexploitation and insufficient recharge. However, the complex subsurface geometries hamper hydrogeological modeling, characterization, and effective management. Reliably estimating aquifer substrate topography is critical for groundwater models but is challenged by limited direct measurements. This study develops nonlinear machine learning models to infer substrate depths by fusing sparse borehole logs with regional geospatial data. A Gaussian process regression approach provided robust holistic mapping, leveraging flexibility, and uncertainty quantification. Supplementary neural network architectures focus on isolating specific variable relationships, like surface elevation–substrate. Model accuracy exceeded 0.8 R-squared against validation boreholes. Spatial visualizations confirmed consistency across landscape transects. Elevation and piezometric data proved most predictive, though multivariate inputs were required for the lowest errors. The results highlight the power of statistical learning to extract meaningful patterns from disparate hydrological data. However, model opacity and the need for broader training datasets remain barriers. Overall, the work demonstrates advanced machine learning as a promising avenue for illuminating complex aquifer geometries essential for sustainability. Hybrid approaches that use both data-driven and physics-based methods can help solve long-standing problems with hydrogeological characterization.

ERT-based experimental integrated approach for soil hydrological characterization in rainfall-induced shallow landslides prone areas

Shallow landslides triggered by heavy rainfalls are slope instabilities, developed in the most superficial eluvial layers, involving the first 2 m from the ground level. A crucial predisposing factor in shallow landslides occurrence is the soil water content, generally measured trough sensors installed in the first soil layers. However, despite being a very precise approach, this monitoring technique provides for a site-specific dataset. An integrated method to extend the hydrological characterization from site-specific to slope scale is presented, combining geotechnical analyses, field data monitoring, and geophysical investigations, in two experimental test sites located on Italian Apennines. Ten Electrical Resistivity Tomographies (ERT) of the first soil horizons were performed through different array geometries (2D-3D-Time-Lapse), calibrated and interpreted basing on stratigraphic logs, trenches, and monitored soil water content field data. The test sites colluvial covers composition was analyzed and compared to resistivity values to build conceptual hydrogeological models of the deep-water circulation. In addition, two time-lapse (4D) ERT surveys were performed in both test sites simulating very intense precipitations, to determine the resistivity variations at different soil drainage conditions, thus estimating the average bulk permeability. Bulk permeability can be also a useful input parameter for slope stability models, widely employed in engineering practices. This integrated method proved to be very useful for the hydrogeological characterization of the subsoil at slope scale, where it is susceptible to slope instability, improving the knowledge of water circulation, as well as the bulk permeability heterogeneities, which are shallow landslides triggering parameters.

Mapping saltwater intrusion via Electromagnetic Induction (EMI) for planning a Managed Aquifer Recharge (MAR) facility in Maltese Island

In coastal areas, saltwater intrusion causes a depletion of the resource by reducing potable and irrigation freshwater supplies and causing severe deterioration of groundwater quality. This trend is observed in Pwales Valley, in the North part of Malta where the management of water resources plays a crucial role for the environmental sustainability of the area, given the importance of intensive agricultural activity along this valley. In order to tackle such phenomenon, actions or adaptation measures against climate change are strongly required. For example, Managed Aquifer Recharge (MAR) is an increasingly important water management strategy to maintain, enhance and secure stressed groundwater systems and to protect and improve water quality. To accurately plan a Managed Aquifer Recharge scheme, it is crucial to define a hydrogeological model of the studied area, with the use of traditional hydrogeological measurements and innovative unconventional techniques. In recent years, Electromagnetic Induction measurements, based on induction of em fields, have been increasingly used for investigating the saltwater intrusion dynamics due to their high sensitivity to the salinity. In the study area of Pwales Valley, a Managed Aquifer Recharge scheme is being planned and, for this aim, a hydrogeological model has been developed through an Electromagnetic Induction survey. More than 20,000 apparent electrical conductivity (ECa) data were collected to generate a quasi 3D high-resolution model of electrical conductivity of the Pwales Valley. The results highlighted the spatial extension of the tongue-shape salt water intrusion from east to west along the valley, as well as some geological-hydrogeological peculiarities such as the thickness of the salt wedge and the irregular top surface of the bottom impermeable layer, otherwise undetectable with other direct techniques at the field scale resolution. The approach was confirmed to be a useful tool for an effective hydrogeological characterisation, essential for planning adaptation measures to a changing climate, such as the implementation of a Managed Aquifer Recharge scheme.

Multiphysics monitoring of cementation operation: implications for wellbore integrity and hydrogeological characterization

The application of optical fibers for assessing cemented wellbore’s integrity attracted considerable attention recently, because of low cost, decent temporal/spatial resolution and absence of downhole electronics. This study presents an integrated approach to compare measurements from distributed temperature sensing (DTS), distributed strain sensing (DSS) and fiber Bragg grating (FBG), at different stages of the wellbore cementation at Bedretto Underground Laboratory for Geosciences and Geoenergies. Before the cementation, the measurements from DTS provided information about the hydrogeological settings of the wellbore, including the major flow zones, and presence of a highly conductive hydraulic shortcut to a nearby wellbore. During the cement injection, the temperature sensors (DTS and temperature FBG) clearly detected the evolution of the top of the cement. While the mechanical deformation sensors (DSS and strain FBG) did not provide significant insights during this stage, their role became more pronounced in subsequent phases. Results show that the irregularities on the wall have minor influence on the thermo-mechanical response of the wellbore, both during and after cementation. After cementation, the temperature sensors (DTS and temperature FBG) traced different phases of cement-hardening process, while DSS measurements identified areas of major deformation, primarily in fracture/fault zones. It was also observed that localized elevation of temperature and extensional deformation along the wellbore during the cement-hardening are correlated with the presence of permeable structures, most likely due to continuous supply of water. Results of this study show that monitoring of the cemented wellbores using optical fibers, in particular during cement hardening, not only can be used to efficiently assess the wellbore integrity but also can provide us additional important information about the hydrogeological settings of the target reservoir volume.

Uranium anomaly in groundwater of the hard rock aquifer system in southeast Brazil

This study presents a hydrogeological characterization that fills knowledge gaps in an area where a complex geological scenario connects two fractured (granite/metamorphic rocks and diabase) and one porous (sedimentary rocks) aquifer systems. Previous groundwater studies from the four local deep supply wells suggested the sedimentary aquifer as the source of uranium (∼60 μg/L) in one of the wells. Despite the water extraction interruption from this well, this finding needed to be supported by evidence provided by the geological and structural characteristics of the aquifers. Data collected through video inspection, caliper, optical (OPTV), and acoustic borehole televiewers (ATV) revealed the predominance of the crystalline aquifer in the area. As recorded by video inspection, the well's borehole with high U intersects the crystalline rocks at several open fractures and presents the highest gamma radiation values. Therefore, we infer that the origin of dissolved U is the weathering of primary minerals locally occurring in those rocks. The U leaching and complexation as calcium-uranyl-carbonates favors its solubility in that specific aqueous medium, as shown by hydrogeochemical modeling using PHREEQC. Additionally, the major ions and trace elements concentrations allow the division of the wells into two groups: a) two with higher U concentrations, influenced by the granite/metamorphic aquifer and possibly longer residence times, and b) the other two wells with lower U concentrations, higher nitrate concentrations, influenced by the diabase aquifer, possibly have younger residence times.

Hydrogeological characterization of the Silala River catchment

AbstractThis article reviews hydrogeological studies carried out between 2016 and 2018 in the Silala River basin, a catchment shared by Chile and Bolivia. These were conducted in the context of the Case Concerning the Status and Use of the Waters of the Silala River, submitted to the International Court of Justice in 2016, and contributed to multidisciplinary science to demonstrate that this system is an international watercourse. In 2016, the hydrogeological understanding of the Silala River basin was poor. The studies reviewed here filled many knowledge gaps, providing a solid hydrogeological baseline, and establishing new monitoring infrastructure to collect relevant aquifer data. The most important hydrogeological units were identified as the fluvial deposits, alluvial deposits, and the Cabana ignimbrite. The latter is highly heterogeneous, weathered and fractured, and exhibits a high permeability. It is the most important unit in terms of productivity, and is the major regional aquifer providing spring flows to Bolivian wetlands and groundwater flow across the international border. The studies provided a preliminary understanding of the main aquifers in Chile and their properties, which underpinned the development of a robust hydrogeological conceptual model of the system, reviewed elsewhere in this special issue. Subsequent refinements are also summarized. This work confirmed that both surface water and groundwater flows from Bolivia to Chile, and thus confirms the status of the Silala River as an international watercourse and provided the basis for a basin‐scale groundwater numerical model, used to investigate the impact of wetland channelization on surface water/groundwater partitioning.This article is categorized under: Science of Water > Hydrological Processes

Limpopo National Park (Mozambico): groundwater assessment as a tool for a sustainable management of the area

This paper deals with updated results coming from hydrogeological studies carried on the framework of the SECOSUD Phase II, called “Conservation and equitable use of biological diversity in the SADC region (Southern African Development Community), a project supported by the Italian Ministry of Foreign Affairs in the SADC, whose focus area includes South Africa Development Countries. The main goal of the SECOSUD Phase II Project is the definition and implementation of scenarios for sustainable development, aimed at an equitable conservation of biodiversity resources and, as a consequence of this target, the hydrogeological characterization, with the groundwater recharge assessment, of this area and its buffer zone. Limpopo National Park is one of the jewels in the crown of Mozambique’s protected areas. As a matter of fact, sustaining the conservation of biodiversity, due to its complexity and multiple drivers, which stress it, is on first a matter of water environment assessment, as most ecosystems are highly dependent on the hydrological cycle and groundwater availability. After gathering regional and local geological data, which let us set up a detailed geological map of the area under study, pointing out the main outcropping geological units, with their main hydrogeological properties, the methodological approach adopted has been to assess the potential infiltration, applying the Inverse Hydrogeological Budget Technique, performed for the focus area. Because of the lack of meteorological data referred to Limpopo National Park, it has been applied a spatial distribution of precipitation measurements, collected in many gauge stations, located in the Kruger National Park during the last 54 years, which represent an interesting rainfall historical series. The target of the study has been to assess a trend of meteorological data with the aim of understanding how precipitations could affect groundwater recharge, and their influence on groundwater availability. The estimation of groundwater recharge is the tool for suggesting better water management in the area, aimed to preserve as much biodiversity as people living in the buffer zone.

A Hydrogeological Conceptual Model Refines the Behavior of a Mediterranean Coastal Aquifer System: A Key to Sustainable Groundwater Management (Grombalia, NE Tunisia)

The Mediterranean coastal aquifer system of the Grombalia basin (NE Tunisia) offers immense potential as a source of fresh water for agriculture, industry, and drinking water supply. Nonetheless, due to its intricate hydrogeological characteristics and the prevailing issue of groundwater salinity, comprehending its groundwater system behavior becomes crucial for the effective and sustainable management of this aquifer system. Based on the hydrogeological characterization of the Grombalia basin, a novel 3D hydrogeological conceptual model was developed to enhance the understanding of its complex aquifer system. The integration of insights from geological, hydrogeological, hydrodynamic, and hydrochemical components facilitated the construction of the hydrogeological conceptual model. Although the model’s validity faced initial uncertainties due to spatial interpolation of lithological sequences, this study’s thorough and encompassing hydrogeological investigation overcame these limitations. As a result, a more informed comprehension of the aquifer system complexities was achieved. This study reveals that the basin is underlain by an extensive, cohesive Mio–Plio–Quaternary aquifer system. The model demonstrates vertical and lateral hydrogeological continuity between the Quaternary and underlying Mio–Pliocene deposits, enabling groundwater flow and exchange between these layers. Over-abstraction of the Mio–Plio–Quaternary aquifer system has led to a significant drop in piezometric levels and raised the risk of seawater intrusion. These findings emphasize the critical necessity of taking into account the interconnections among hydrogeological units to ensure sustainable groundwater management. The developed conceptual model offers a key tool for understanding the hydrodynamic functioning of the Grombalia aquifer system with a view toward guiding future groundwater management strategies. The application of this approach in the Grombalia basin suggests its potential applicability to other regional aquifers facing comparable challenges.

Long-term groundwater geochemical evolution induced by coal mining activities-a case study of floor confined limestone aquifer in Yaoqiao Coal Mine, Jiangsu, China.

Groundwater chemical composition can be changed due to long-term coal mining activities, but it was unclear how it was induced in Taiyuan Formation limestone (TFL) regarding the lack of relevant quantitative studies. The aim of this research is to improve understanding of the chemical composition changes in groundwater of L4 limestone in the coal mining area based on the available hydrochemical and hydrodynamical reports and studies during the period 1978-2020. The systematical analysis of the groundwater composition and field allows to make the hydrogeological characterization with the relatively independent blocks by the factor groups "Planar division & Vertical zonation" and "High water pressure, Poor recharge & Little water inflow," which determines different hydrochemical types and high TDS concentration. The long-term groundwater drainage has caused the eastern and southern limestone aquifer to demonstrate a wide range of depression cones and depletion of groundwater resources, the majority areas were dewatered, and the karstification process changed significantly. An analysis of chemical compositions changes due to extensive permanent drainage of L4 limestone water revealed the decrease in the TDS concentration. The solubility of calcite, dolomite, and gypsum changed, which resulted in the decreasing tendency of Ca2+ + Mg2+ ions. Evaporation and concentration were found to be the main factors determining the L4 limestone water composition, whereas ion exchange was the primary factor for rock-water interaction. These findings are helpful for mine enterprises to take necessary measures for preventing and controlling the groundwater quality degradation from the extensive coalmine drainage.

Hydrogeological characterization of karst springs of the white (Proteus anguinus anguinus) and black olm (Proteus anguinus parkelj) habitat in Bela krajina (SE Slovenia)

The springs west of Črnomelj, in SE Slovenia, are the habitat of the black (Proteus anguinus parkelj) and the white olm (Proteus anguinus anguinus). Some of these springs are also the only known habitat in the world of endemic species of black olm. A steady decline in olm populations has been observed in this area over the past decades. Owing to the rapid runoff and groundwater flow high-resolution monitoring is essential in providing better insight into the hydrogeological characterization of the catchment area of springs. Specific factors and critical parameters of water behind said olm degradation have not yet been defined. Because the olm’s environment is largely aquatic, one potential critical parameter could be the higher water temperatures (>12 °C) or higher nitrate concentration (>9.2 mg/l). The six-month observation of the springs (July – December 2021) point to water temperature as a potential critical parameter since the water temperature of the springs exceeded 12 °C in months July and August. Nitrate concentrations could also be a second critical parameter in the degradation of the olm’s habitat. Maximum nitrate concentrations above 9.2 mg/l throughout much of the observation period (except for Dobličica spring). Due to less agricultural activity in December in the spring catchment area and a higher dilution rate due to reduced evapotranspiration and increased effective precipitation during this time of the year, the nitrate concentrations are decreased. The results of the measured parameters of groundwater could show the hydrogeological connection between the Otovski and Pački breg springs and between Šotor, Jamnice and Dobličica. The Obršec spring has an independent catchment area. A detailed estimation of the springs catchment area is possible due to a detailed geologic map. It is necessary to determine the origin of the nitrate (nitrate isotope analysis), to quantify the threshold values of the critical parameters, to define precisely all the causes of the olm deterioration, and to make proposals for appropriate measures to limit or even stop the decline of the olm population.

The Delineation of the Langat Basin Aquifer Based on Geological and Hydrogeological Characterization of Three Urban Areas of Malaysia

The Delineation of the Langat Basin Aquifer Based on Geological and Hydrogeological Characterization of Three Urban Areas of Malaysia

A study on hydro-geological characterization through Dar-Zarrouk parameters in hard rock terrain of Mandavi River Basin, Andhra Pradesh, India

A study on hydro-geological characterization through Dar-Zarrouk parameters in hard rock terrain of Mandavi River Basin, Andhra Pradesh, India

Influence of the Construction of the Urdinbide Road Tunnel on the Autzagane Aquifer in Biscay (Spain)

The Urdinbide road tunnel goes through the Autzagane aquifer. This important aquifer is located within the hydrogeological area of the Urdaibai Biosphere Reserve, one of the most important biosphere reserves in the Iberian Peninsula, and it is also used as a source of drinking water for some urban areas in the municipality of Amorebieta-Etxano. The construction of the tunnel could pose a potential risk to the normal functioning of the aquifer, so its design included a special procedure for injecting cement and microcement to waterproof the surrounding area of the drilling, preventing the tunnel from functioning as a drain for the aquifer. The project initially included an intensive hydrogeological characterization of the rock massif, as well as a monitoring phase during the construction works, which allowed a real-time verification of the influence of the tunnel construction on the functioning of the aquifer and the restoration of its normal functioning once the works were completed. The work carried out has shown that the construction of the tunnel has not caused a significant impact on the Autzagane aquifer.

Petrophysical and hydrogeological characterization of coastal aquifer using geophysical logs in Lekki Peninsula, Lagos, Nigeria

The coastal aquifers of Lekki Peninsula, Lagos are increasingly threatened by saline water invasion. In this study, the characterization of the petrophysical properties of the coastal aquifers in Lekki Peninsular through analysis of geophysical logs was carried out. The methodology involved editing, interpolation, depth shifting and normalization of gamma ray and resistivity logs from twelve water wells. Log analysis was employed to map aquiferous units and determine their petrophysical properties which include clay volume, porosity, permeability, water resistivity, total dissolved solid and water quality. These properties were further subjected to cross plot analysis. The results identified three aquifers. Aquifer 1 is mostly unconfined shallow phreatic aquifer characterized by 11–35% porosity. The TDS ranges from of 4.63 mgL−1 – 50.33 mgL−1. The intermediate Aquifer 2 is characterized by significant thickness (25–75 m), clay volume (0.22–0.54) excellent porosity (16–27%), permeability (99–110 mDarcy), water resistivity (25–175 Ωm) and total dissolved solids of <30.00 mgL−1. The deep Aquifer 3 lies at 153–255 m depth and has total dissolved solids value of 10.63 mgL−1 and 26% porosity. Cluster analysis shows 67% of wells that penetrated Aquifer 2 encountered saline to brackish water while 40% found aquitard with poor petrophysical properties. Water wells in the study area should target aquifer 3 as Aquifer 2 is prone to saltwater intrusion due to over-pumping. This study furnishes information that enables sustainable future exploration, exploitation, monitoring and management of groundwater reserve in Lekki Peninsula.

Hydrogeology of Karst and Metapelitic Domains of the Semi-Arid Vieira River Watershed (Brazil)—A Contribution to Groundwater Resource Management

Water scarcity is a problem in Brazil’s northern semi-arid domain. Montes Claros is the most populated Minas Gerais city in this context, and its socio-economic problems are related to water consumption and management. Aiming to help assess these problems, this study presents a new hydrogeological characterization. The 3D geological model was developed using drilling data from 125 public wells, field campaigns and satellite images for hydrogeological interpretation. The area has two main different aquifer systems underlying the Vieira River Watershed. The first is a karstic fissured aquifer, located in the Lagoa do Jacaré limestone Formation. The second is fissured aquifer systems in metapelites from the Serra da Santa Helena and Serra da Saudade Formations, which are characterized by low hydraulic transmissivity and locally higher specific capacity zones related to their structural features or carbonate intercalations. Monitoring data from new manual and automatic methods carried out in 16 selected points highlight that variations are related to (1) hydrogeological domains, (2) oscillations related to interference from neighboring wells, and (3) seasonal variation and irregular pluviometry in the region. This is important information that can help update our hydrogeological knowledge, provide information on surface and groundwater flow dynamics, and improve water resource management, with the aim of ensuring sustainability in exploitation.

Understanding the Silala River—Scientific insights from the dispute over the status and use of the waters of the Silala (Chile v. Bolivia)

AbstractThe flows of surface water and groundwater from the Andes to the Atacama Desert are a vital source of freshwater, supporting ecosystems and human activities, but few substantive studies have addressed the hydrological and hydrogeological functioning of these systems. A dispute between Chile and Bolivia concerning the transboundary Silala River, recently heard before the International Court of Justice, The Hague, provided a unique opportunity for new scientific studies, reviewed in this Special Issue. First, findings from field studies that address the geological and geomorphological evolution of the Silala River basin and its current status, the key hydrological processes (including infiltration, actual evaporation from wetlands and alluvial plains, and surface water‐groundwater interactions), and the hydrogeological characterization of the major aquifers are reviewed. The dispute arose because Bolivia disagreed that the Silala was a transboundary river, subject to international law. As the Court proceedings evolved, this was accepted by Bolivia, but effects on surface flows of historical channelization in the Bolivian headwater wetlands remained a point of legal and technical disagreement. Bolivia asserted large increases in surface flow, based on modeling by their consultants, DHI. Chile held that these effects are small. In the second part of this paper, we summarize the modeling evidence. Chile's use of DHI's models, and its own hydrological and groundwater modeling of the basin, fully support Chile's position. We conclude with discussion of the Court's judgment, the challenges of physically‐based modeling of small changes in complex systems, and associated implications for judicial practice.This article is categorized under: Human Water &gt; Water Governance Science of Water &gt; Hydrological Processes Science of Water &gt; Water and Environmental Change