Groundwater Flow Patterns Research Articles

Boundary-to-solution mapping for groundwater flows in a Toth basin

In this paper, the authors propose a new approach to solving the groundwater flow equation in the Toth basin of arbitrary top and bottom topographies using deep learning. Instead of using traditional numerical solvers, they use a DeepONet to produce the boundary-to-solution mapping. This mapping takes the geometry of the physical domain along with the boundary conditions as inputs to output the steady state solution of the groundwater flow equation. To implement the DeepONet, the authors approximate the top and bottom boundaries using truncated Fourier series or piecewise linear representations. They present two different implementations of the DeepONet: one where the Toth basin is embedded in a rectangular computational domain, and another where the Toth basin with arbitrary top and bottom boundaries is mapped into a rectangular computational domain via a nonlinear transformation. They implement the DeepONet with respect to the Dirichlet and Robin boundary condition at the top and the Neumann boundary condition at the impervious bottom boundary, respectively. Using this deep-learning enabled tool, the authors investigate the impact of surface topography on the flow pattern by both the top surface and the bottom impervious boundary with arbitrary geometries. They discover that the average slope of the top surface promotes long-distance transport, while the local curvature controls localized circulations. Additionally, they find that the slope of the bottom impervious boundary can seriously impact the long-distance transport of groundwater flows. Overall, this paper presents a new and innovative approach to solving the groundwater flow equation using deep learning, which allows for the investigation of the impact of surface topography on groundwater flow patterns.

Analisis Pola Aliran dan Kuantitas Air Tanah Dangkal di Kota Madiun

<p><em>The increasing physical development and decreasing water infiltration areas have led to a reduction in groundwater reserves. Groundwater is experiencing a decline both in quantity and quality over time. The rising demand for water is inversely proportional to the diminishing availability of water in terms of quality. This situation also implicates a decrease in the quantity of groundwater. Integrated protection and management efforts must be carried out from upstream to downstream, one of which can be achieved through groundwater conservation. Therefore, the aim of this research is to understand the shallow groundwater flow patterns in the city of Madiun. This study conducted an inventory, identification, and mapping of the area to determine the criticality of shallow groundwater in terms of quantity using the shallow groundwater flow pattern analysis method. The results of the analysis generally indicate that the direction of shallow groundwater flow in the city of Madiun, in the eastern areas of the Madiun River, flows from south to north, while in the western areas of the Madiun River, it flows from west to east, all ultimately leading towards the Madiun River.</em></p>

3D Discrete Fracture Network Modelling from UAV Imagery Coupled with Tracer Tests to Assess Fracture Conductivity in an Unstable Rock Slope: Implications for Rockfall Phenomena

The stability of a rock slope is strongly influenced by the pattern of groundwater flow through the fracture system, which may lead to an increase in the water pressure in partly open joints and the consequent decrease in the rock wall strength. The comprehension of the fracture pattern is a challenging but vital aspect in engineering geology since the fractures’ spatial distribution, connectivity, and aperture guide both the water movement and flow quantity within the rock volume. In the literature, the most accepted methods to hydraulically characterise fractured rocks in situ are the single borehole packer test, the high-resolution flow meters for fractures, and the artificial tracer tests performed in boreholes. However, due to the high cost a borehole requires and the general absence of wells along coastal cliffs, these methods may not be appropriate in rockfall-prone areas. In this study, an unsaturated rocky cliff, strongly affected by rockfalls, was investigated by combining kinematic analysis, Discrete Fracture Network (DFN) modelling, and artificial tracer tests. The DFN model and potential rock block failure mechanisms were derived from high-resolution 3D virtual outcrop models via the Structure from Motion (SfM) photogrammetry technique. An artificial tracer was injected using a double ring infiltrometer atop the recharge zone of the slope to determine the infiltration rate and validate the DFN results. The DFN and tracer test methods are frequently used at different spatial scales and for different disciplines. However, the integration of digital photogrammetry, DFN, and tracer tests may represent a new step in rockfall and landslide studies. This approach made possible the identification of groundwater flow patterns within the fracture system and revealed about a 10-day tracer transit time from the injection area and the monitored slope, with similar conductivity values gathered from both the DFN and tracer test. Planar and wedge failures with volumes ranging from 0.1 and 1 m3 are the most probable failure mechanisms in the areas. The results were consistent with the delay between the intense rainfall and the slope failures previously documented in the study area and with their mechanisms.

Месторождения урана под экраном многолетнемерзлых пород как природная аналогия геологического хранилища на период предстоящего похолодания климата

The article evaluates the conditions at the site proposed for a geological radioactive waste (RW) disposal facility (DGR) considering the scenario of the upcoming climate cooling. The evaluation is based on the analogy method with the comparison made against modern conditions explored at uranium deposits confined to the permafrost zone. The analogy is based on modern hydrogeological data from the Transbaikalia deposits explored using the underground borehole leaching method. This method yields no significant disturbance of the groundwater flow patterns. The study provides comparative analysis of climatic, geological and hydrogeological characteristics of the DGR siting area in the Krasnoyarsk Territory and those of uranium deposits in Transbaikalia. The limitations of this method have been validated. The paper highlights the main characteristics of groundwater flows in sub-permafrost aquifers. The results obtained may prove to be helpful in the development of models demonstrating radionuclide transport from the DGR developed at the Yeniseiskiy site.

Recharge Zone of Shallow Groundwater at Southeastern Part of Kulon Progo District Area based on Groundwater Facies

The Galur and Lendah areas are in the southeastern part of Kulon Progo Regency, Yogyakarta, Indonesia. This area has become a developing area because of the new airport in this district. Along with its development, the need for groundwater in this area is increasing, so groundwater research is also increasingly needed. A study on groundwater is required to support the development of this region. This time, a groundwater study was conducted to determine the potential for the recharge-discharge zone, also groundwater flow patterns based on the chemical facies of the groundwater. The hydrogeological survey was carried out with groundwater sampling from 9 (nine) dug wells and 1 () spring for physical/chemical testing of groundwater in the laboratory. The results showed groundwater in the study area generally flows south or northwest, with a radial pattern anomaly in the north. The shallow groundwater studied was bicarbonate type with Ca, Na, and Mg cations variations. The groundwater facies characterizes groundwater that is typical in the catchment

PEMANFAATAN TEKNOLOGI SISTEM INFORMASI GEOGRAFI UNTUK PEMETAAN POLA ALIRAN AIR TANAH DI KECAMATAN LIMBOTO

Limboto Subdistrict, which is the capital of Gorontalo Regency, has fairly high population growth and is an area that is vulnerable to the effects of drought. This causes the availability of groundwater to decrease. This study aims to utilize the GIS application to determine the pattern of groundwater flow in the Limboto District. This groundwater flow pattern can be used as a reference for further research related to groundwater. The type of data in this study is the type of primary data. The method used in this research is a survey method, namely by measuring directly in the field. The data analysis technique used to determine the pattern of groundwater flow in Limboto Regency is utilizing software (GIS) using ArcGIS 10.7 software to obtain a map of groundwater flow patterns in Limboto District. The results of the spatial analysis of the groundwater flow pattern map in Limboto District show that water flows from the northern part of the study site to the southern part of the study site.

Deep Groundwater Flow Patterns Induced by Mine Water Injection Activity

Mine water injection into deep formations is one of the effective approaches for reducing the drainage from coal mines in the arid and semi-arid region of the Ordos basin, China. Many coal mines are attempting to execute the related projects. Under the influence of groundwater protection, the understanding of regional groundwater flow is becoming highly important to the mine water monitoring, whereas quite few academic research teams focus on the deep groundwater flow pattern by mine water injection. This paper reveals the spatial distribution of Liujiagou Formation that is in positive correlation with the terrain, and its local thickness is influenced by the dominant W-E and NE-SW directions of geological structures. Only a part of sandstone rocks consists of aquifers, the rest 61.9% of relatively dry rock provide the enhanced storage space and partial mudstone aquicludes decrease the possibility of the vertical leakage for mine water. The dynamic storage capacity is evaluated at 2.36 Mm3 per 1 km2 and over 25.10 billion m3 in this study area. Two hydrogeologic cross-sections of basin-scale identify the W-E and N-S regional groundwater flow directions, with the lower Yellow River catchment becoming the discharged region. The hierarchically and steadily nested flow systems containing coal mining claims are influenced by coal mining activity. The groundwater depression cone in a shallow coal measure aquifer is caused by mine water drainage whereas the groundwater mound in Liujiagou Formation is generated by mine water injection activity. The numerical simulation revealed that the groundwater head rebound is slightly decreased and will not recover to its initial baseline within 500 years due to its low porosity and permeability. This study elucidates the deep groundwater flow patterns induced by mine water injection and provides a practical methodology for the management and pollution monitoring of mine water injection activity.

Groundwater flow patterns in a coastal fen exposed to drainage, rewetting and interaction with the Baltic Sea

Low-lying coastal peatlands are unique ecosystems where water levels and salt input with seawater determine vegetation and greenhouse gas emissions, while the export of nutrients and carbon via submarine groundwater discharge influences biogeochemical processes in shallow coastal sediments. Anthropogenic interferences like drainage and diking strongly impact the water flow. This study aimed at understanding the hydrological system in a rewetted coastal fen typical for the southern Baltic Sea. Groundwater observation wells were installed both in the peat layer and underlying sands, and continuous readings of water levels and specific conductivities were combined with groundwater dating and major ion composition analyses. Apparent tritium–helium groundwater ages between 7 and more than 60 years in the shallow aquifer below the peat revealed a long memory of the system. Recharge through the peat layer was identified as a major source of groundwater from neon and helium isotopes in combination with water levels. Chloride concentrations showed a homogeneous fraction of 30 % sea water throughout the aquifer despite differing groundwater ages. Drainage ditches still affect groundwater flow today depending on the peat and aquifer thickness. Both nutrient-enriched, brackish, deeper groundwater and freshwater from the precipitation-fed dune dike discharge to the sea. We conclude that rewetting of coastal peatlands mainly affects the groundwater in the upper peat, with little impact on the underlying aquifer, and might revive submarine groundwater discharge and associated nutrient fluxes despite low hydraulic gradients.

Podzemní vody hluboké struktury regionálního rozsahu: Pasohlávky–Laa an der Thaya

The regions of South Moravia in Czech Republic and Lower Austria are well-known for their use of thermal mineral waters for balneological purposes. Mineral waters are exploited from a Jurassic aquifer by two about 1.5 km deep wells MUS-3G (Pasohlavky, Czech Republic) and Laa TH Nord 1 (Laa an der Thaya, Austria). This Jurassic aquifer buried below the Neogene foredeep overlies a crystalline basement of Bohemian Massif and continues to the southeast below the Western Carpathians. Jurassic sediments which are mainly composed of autochthonous carbonates increase their thickness in this direction due to the decline of the crystalline basement. Because of this decline, there are two developments of Jurassic sediments, the shallower on the northwest and the deeper on the southeast. The zone between these two developments is known as the Mušov transition zone. For sustainable mineral water resources development, a groundwater flow pattern and recharge are evaluated. This evaluation includes both the hydrogeologic structure of Jurassic carbonates and hydraulically continuous underlying and overlying rocks. Because of the considerable depth of this hydrogeologic structure, which ranges from 100 to 3 000 metres below sea level, this study was based mostly on archive reports related to deep wells at the study area. The extent of studied units was identified on well-log data and geophysical survey interpretation. The resulting groundwater level contour map is based on the spatial distribution of hydraulic heads ranging approx. from 180 to 220 metres above sea level (masl) that were derived from pressure and water density conditions at the Jurassic aquifer. The general direction of groundwater flow is from northwest and southeast to the drainage zone (hydraulic head approx. 170–190 masl) identified in the middle of the studied area, which is identical to a course of the Mušov transition zone and parallel to the course of Dyje river (water table 170–180 masl). The northwestern part of the studied hydrogeological structure also differs from the southeastern part in a lower total mineralization which indicates active inflow of fresh water. The study was also enhanced by a spatial distribution of hydraulic parameters of all modelled units. These parameters were derived from hydrodynamic tests. The hydraulic conductivity values for the major Jurassic aquifer range from 6.0 × 10-4 to 1.3 × 10-9 m/s. The occurrence of the higher hydraulic conductivity near the drainage zone indicates the presence of a well-developed drainage network.

Groundwater responses to recharge and flood in riparian zones of layered aquifers: An analytical model

A riparian zone is an important element in a river-aquifer system, controlling water exchange and other chemical and biological processes between a river and an aquifer. Complex groundwater flow patterns may occur due to aquifer heterogeneity within a riparian zone. The purpose of this study is to investigate the impacts of layered heterogeneity on water exchange in the riparian zone using a mathematical model for groundwater flow in a two-layer aquifer that is recharged by precipitation and floods. A semi-analytical solution is derived for the hydraulic head, lateral discharge, and fluxes between the layers. Results demonstrate that the hydraulic conductivity difference between the two layers enhances lateral flow in the higher permeable layer and, more importantly, generates vertical flow between the two layers. The vertical flow induced by the recharge event is downward while it could be upward or downward induced by the flood event, which is determined by the contrast in permeabilities of the two layers. Using an equivalent hydraulic conductivity approach underestimates discharge of the two-layer aquifer due to recharge or flood. The analytical solution closely matched the observed hydraulic heads in riparian zone well of White Clay Creek and provided reasonable estimates of aquifer parameters. The present solution provides a valuable basis for further study of chemical and biological processes in riparian zone.

The Impact of Ice Sheet Geometry on Meltwater Ingress and Reactive Solute Transport in Sedimentary Basins

AbstractWe investigate the effect of ice sheet geometry on groundwater flow patterns and meltwater ingress in a hypothetical sedimentary basin. The simulation results indicate that meltwater ingress is much greater in 3D domains with a relatively narrow ice sheet extent compared to a wide ice sheet, or a simplified 2D model. In high permeability units (HPUs), the simulated meltwater penetration depth can reach up to 750 m in 3D domains compared to 400 m in a comparable 2D domain. In low permeability units (LPUs), very limited meltwater penetration occurs, indicating that ice sheet geometry and model dimensionality do not substantially affect water flow in these units. A conservative tracer, with a source located at a depth of 500 m in both HPUs and LPUs, illustrates that solutes can be transported to greater depths in HPUs for a narrow ice lobe scenario, in comparison to a wide ice sheet or the 2D approach. Tracer transport in LPUs is unaffected by ice sheet geometry. Similarly, simulation results indicate that the ingress of dissolved oxygen (O2) into HPUs is most substantial below a narrow ice lobe, while O2 ingress into LPUs is not affected by ice sheet geometry. The numerical experiments indicate that 3D analysis will give more comprehensive results for flow patterns and reactive solute transport subjected to glaciation/deglaciation cycles in the case of a narrow ice lobe, but also suggest that a 2D approach might provide an adequate representation for the case of a relatively wide ice sheet.

Groundwater Modeling: A Tool for Groundwater Management to Support Urban Water Supply and Food Security

Faisalabad is the 3rd largest city of Pakistan where underlying aquifer mostly contains saline water. Heavy population of the city needs huge quantity of fresh water. Water requirements for the existing Faisalabad city are being met by installation of well-fields along Jhang Branch canal, where groundwater is fresh. The increasing population pressure requires more water and identify more suitable sites for installation of well-field on sustainable basis. It was deemed imperative to elevate the existing well field. The MODFLOW, a numerical groundwater model developed by United States Geological Survey (USGS) for simulation and future prediction of aquifer behavior in response to pumping by various well fields was developed, calibrated and validated satisfactorily. A groundwater decomposition approach was also developed to tune various coefficients used in estimation of inflow and outflow components of groundwater system. The calibrated model was used to predict the future response of aquifer under different scenarios of pumping by existing and future/proposed wellfields. Calibrated flow model revealed that a sink has already been developed at the center of existing well-field of Water and Sanitation Agency (WASA) due to excessive pumpage. Future predictions of model indicate that there is no conspicuous change in regional groundwater flow pattern, even with all the existing tubewells remain in operation. However, the sink in the WASA well field area further deepens, and flow gradients become comparatively steep showing increase in groundwater flow velocity. Depth to watertable has already increased from 12 m in 2005 to 16 m in 2011 in the critical area of WASA well field. Model has predicted that this depth will further increase to 24 m in 2018. It has also been observed that groundwater quality along the river is fresh and becomes saline towards Faisalabad city. Due to pumpage in the freshwater zone model predicts that saline water will rush towards well fields deteriorating the quality of fresh water along Jhang Branch Canal. Therefore, it has been suggested that site for further pumping should be moved towards upstream of Jhang Branch Canal at least up to RD 180-187 and possibly on right side of the canal instead of left side

Vertical nitrate migration and denitrification zones in a regional recharge area (Lwówek region, Poland)

We examine the influence of groundwater flow patterns and denitrification on nitrate migration in a regional recharge zone. It has been shown that nitrate contamination has a different behaviour in regions where groundwater is exploited (where deep percolation of nitrate takes place) than where natural gradients exist (with no deep aquifer zone contamination). Multicomponent chemical tracers and isotopic methods were used in the investigation. A contaminant plume was discovered in shallow parts of the aquifer which percolated into deeper parts of the flow system in those regions with a downwards gradient induced by groundwater withdrawal, where the influence of denitrification was limited. Local conditions leading to intense denitrification, i.e., local changes in geological conditions (low-permeability silt intercalations), were also documented. Therefore, vertical changes in groundwater chemistry should be examined to ensure groundwater resource management and protection, as these are extremely important in regional recharge zones with a downwards gradient.

Characterizing the hierarchical groundwater flow systems in Karstic Xiangxi River Basin, West Hubei, Central China

Karstification degree is a key factor in controlling the characteristics of karst GFP. In this study, hydrogeology, karst development, hydrograph, artificial and natural tracers and hydrochemistry were integrated to characterize the groundwater flow patterns (GFP) in the Cambrian-Ordovician karst aquifer in Xiangxi River Basin. Groundwater samples were collected from three karst groundwater points: Wulongdong spring (WLD), Shuimoxi spring (SMX), and groundwater exposed by Borehole ZK03 (ZK03), which have different discharge variations. The hydrogeological analysis and the artificial tracer tests showed that groundwater runoff channel for WLD, SMX and ZK03 are dominated by conduits, fracture networks and micro fissures-matrix, respectively. The natural responses (discharge, electrical conductivity and temperature) of WLD to rainfall indicated that flow in this system is discharged by conduit, fracture and matrix, respectively. Stable isotopes (2H, 18O) of precipitation and groundwater suggested that the WLD and SMX recharge at the adjacent zone with mean elevations of 878 m and 676 m, respectively; while ZK03 recharge at mean elevations of 1338 m from thousands of meters away. Mean residence times calculated by artificial and natural tracers (18O, CFC) of conduit flow in WLD (7–19 h), fracture flow in WLD and SMX (243 and 600 days), and matrix flow in ZK03 (41 years) were obviously increased gradually. Hydro-chemical analysis shows that ZK03 has higher concentrations of ions that related to carbonate dissolution, indicating groundwater in ZK03 has longer time to interact with rocks. The results show that GFP in study aquifer are characterized by local fast conduit flow, local intermediate fracture networks flow and regional slow matrix flow with progressively slower groundwater refresh rate. The conceptual model was also proposed to enable a better understanding of groundwater circulation, water resources and vulnerability of the karst system in Central China.

Multivariate Statistical Analysis and Structural Sovereignty for Geochemical Assessment and Groundwater Prevalence in Bahariya Oasis, Western Desert, Egypt

The Bahariya Oasis is an example of an extremely hyperarid environment and it is characterized by an extensive nonrenewable Nubian Sandstone Aquifer System (NSAS), which is deemed the crucial provenance for agrarian and national development ventures. The present work aimed to assess the groundwater occurrences in the NSAS, and to document the main factors that control the geochemistry of the groundwater in the Bahariya Oasis. Groundwater samples were collected from 52 locations in April 2019 and were analyzed for a total of 13 water-quality physicochemical parameters. A diverse geological and structural setup has greatly impacted the groundwater flow pattern and has diverted it towards the NE by the great Bahariya anticline structure, the ENE-oriented Bahariya mid dextral strike-slip fault, and NE-striking normal faults, while NW-oriented normal faults cause the groundwater to diverge perpendicular to the groundwater flow lines. The groundwater is highly contaminated by trace metals (Fe2+ and Mn2+), which exceed the permissible limit for different purposes. Conventional graphical plots and geochemical modeling integrated with multivariate factor analysis (FA) revealed that the chemical composition of the groundwater is strongly affected by its interaction with the lithologies of the NSAS. The dissolution of aquifer host rocks (carbonates and iron oxides) and chloride salts through the infiltration of groundwater, and the incorporation of cations by the ionic exchange of Na+ by Ca2+ in clay minerals, emerged as worthy mechanisms for the groundwater development. Furthermore, the region’s rapidly increasing population, agricultural expansion, and the associated anthropogenic practices have generated a need for groundwater-quality assurance as a prime source of the water supply. Consequently, reducing the effects of the NSAS’s unsustainable extraction requires long-term monitoring and the ongoing evaluation of the groundwater.

Analysis of Groundwater Flow on Hydrogeological for Sustainable Development and Environment in the Ternate Basin, North Maluku Province, Indonesia

The sustainability of water and sanitation management is an important point in the 2021 SDGs program. To support the program, it is important to understand Indonesia's water cycle. Given the variety of characters, topography, and geology between islands in Indonesia can distinguish hydrogeological systems and their interactions with the surrounding environment. The design and management of water resources, especially groundwater, has an important role, considering the basin area is 106 km2, the character of a volcanic island with the name of an active volcano. Topography from 0-8% is a built-up zone, 8-14% is a cultivation zone, 14-45% is a protected forest, and >45% is a stratovolcano peak zone. Island morphology affects groundwater flow patterns. This study aimed to determine the characteristics of groundwater flow in the Ternate basin. Purposive sampling of 56 production wells, transmissivity value, conductivity, aquifer thickness, and topography was analyzed using the Cubic spline interpolation method. The results showed that the direction of flow and groundwater accumulation based on groundwater modeling using the kriging interpolation technique resulted in the interaction of groundwater flow and depression cones in 56 production wells due to the concentration and massive groundwater abstraction in the Ternate Basin. The decrease in groundwater level is fluctuating, from groundwater flows that occur radially-centrifugally, the total reserves of 56 production wells are 46 million m3/day, the average transmissivity value is 2.17 m2/day, production discharge is 51,710 m3/day.

Assessing the Impact of Artificial Recharge Ponds on Hydrological Fluxes in an Irrigated Stream–Aquifer System

Artificial recharge ponds have been used increasingly in recent years to store water in underlying aquifers and modify baseline groundwater gradients or alter natural hydrologic fluxes and state variables in an aquifer system. The number of constructed ponds, their geographic spacing, and the volume of water diverted to each pond can have a significant impact on baseline system hydrologic fluxes and state variables such as groundwater head, with the latter sometimes rising to cause waterlogging in cultivated areas. This study seeks to quantify the impact of recharge ponds on groundwater state variables (head, saturated thickness) and associated fluxes within an irrigated stream-aquifer system. We use a numerical modeling approach to assess the impact of a set of 40 recharge ponds in a 246 km2 region of the South Platte River Basin, Colorado on localized groundwater head, regional groundwater flow patterns, and groundwater interactions with the South Platte River. We then use this information to determine the overall influence of recharge ponds on the hydrologic system. A linked agroecosystem–groundwater (DayCent-MODFLOW) modeling system is used to simulate irrigation, crop evapotranspiration, deep percolation to the water table, groundwater pumping, seepage from irrigation canals, seepage from recharge ponds, groundwater flow, and groundwater–surface water interactions. The DayCent model simulates the plant–soil-water dynamics in the root zone and soil profile, while MODFLOW simulates the water balance in the aquifer system. After calibration and testing, the model is used in scenario analysis to quantify the hydrologic impact of recharge ponds. Results indicate that recharge ponds can raise groundwater levels by approximately 2.5 m in localized areas, but only 15 cm when averaged over the entire study region. Ponds also increase the rate of total groundwater discharge to the South Platte River by approximately 3%, due to an increase in groundwater hydraulic gradient, which generally offsets stream depletion caused by groundwater pumping. These results can assist with groundwater resource management in the study region, and generally provide valuable information for the interplay between pumping wells and recharge ponds, and their composite effect on groundwater–surface water interactions. In addition, the developed linked DayCent-MODFLOW modeling system presented herein can be used in any region for which recharge rates should be calculated on a per-field basis.

Groundwater Pollution Model and Diffusion Law in Ordovician Limestone Aquifer Owe to Abandoned Red Mud Tailing Pit

Red mud is a strong alkaline solid waste pollutant produced in the process of aluminum smelting, which causes great pollution to the regional groundwater environment due to its high content of fluorine and aluminum and high concentration of strong alkali. In this study, fluoride ion was selected as the model contaminant, and a numerical model of the groundwater flow field and solute transport was developed using GMS software to simulate and analyze the migration patterns of fluoride contaminants caused by the red mud pit for the fractured karst geohydrological conditions. The results demonstrated that the groundwater model and flow pattern were mainly controlled by atmospheric precipitation recharge, given flow boundary conditions and leakage of rivers and drains. When the concentration of fluorine pollutants in the red mud yard was 60.0 mg/L, the maximum migration distance of F− in the groundwater of the ordovician limestone aquifer was 473, 1160, 1595 and 1750 m after 1, 5, 10 and 15 years of bottom leakage, and the additional transport distances were 687, 435 and 155 m every 5 years, respectively. The range of F− pollution plume was 0.37 km2, 1.15 km2, 1.95 km2 and 2.14 km2, respectively and the range of newly added pollution plume was 0.78 km2, 0.80 km2 and 0.19 km2, respectively, every five years. Both indicated that with the extension of time, the migration and diffusion rate of pollutants slow down, and the diffusion volume increased first and then decreased. The F− pollution plume spread from the red mud pit to the northeast, which was consistent with the flow of groundwater. The high-concentration pollution plume was mainly distributed in the Ordovician limestone fractured aquifer in the northeast. This study revealed the migration law of red mud pollutants, and provided a scientific decision-making basis for the prevention and control of red mud groundwater pollution in the future.

Groundwater circulation patterns in bedrock aquifers from a pre-selected area of high-level radioactive waste repository based on two-dimensional numerical simulation

Deep geological disposal is internationally accepted as a feasible and safe way to dispose the high-level radioactive waste (HLW) in low permeability fractured bedrocks. It is essential to understand the regimes of groundwater flow, circulation, and predict the characteristics of long-term flow systems for site selection and safety assessment of deep geological HLW disposal by using numerical simulation technology. In this study, TOUGH3/EOS9 software with an improved evaporation module is used to develop a two-dimensional variably saturated numerical model of a typical profile at Xinchang site, which is considered as a potential deep geological repository for spent HLW in China. Results reveal that almost 99% of the precipitation is discharged through evaporation, and less than 1% infiltrates into shallow groundwater. The groundwater flow pattern is closely related to topography and lithological distribution, and the groundwater flow in Xinchang rock mass cannot discharge to the south Hexi Corridor. Groundwater in the typical profile is divided into three types of groundwater flow system, namely local, intermediate and regional flow system, and each has its own characteristics based on aspects of flow path, cycle amount, cycle path, residence time and discharge position. The circulation flux of these three systems accounts for 79.25%, 13.24% and 7.51% of the total groundwater quantity of Xinchang site, respectively. Meanwhile, different-depth models were constructed to validate the influence of bottom boundary depths on groundwater characteristics. Increasing the bottom boundary depth has limited influence on the maximum circulation depth of regional flow system, but negligible impact on circulation flux. This study can enhance the understanding of groundwater circulation and evolution in fractured bedrock aquifers with low permeability, and provide the feasibility of geological repository for spent HLW for the view point of groundwater flow.

The effect of river regulation on groundwater flow patterns and the hydrological conditions of an aapa mire in northern Finland

Study regionNorthern Finland. Study focusThis study examined long-term (decade-scale) hydrological and ecological consequences of dam construction and subsequent river regulation on the environmentally protected Viiankiaapa mire. Pre-regulation floods affected the hydrology of the riverbanks and the Viiankiaapa mire, which contain habitats of flood-dependent or groundwater-influenced ecosystems. Groundwater discharge and flow patterns and pre-regulation flood coverage were simulated to investigate the impact of river regulation on the mire area. New hydrological insights for the regionThe flood models indicate that regular flooding covered the westernmost part of the mire before the regulation. Groundwater modelling suggests that the regulation has raised the locations of springs in the river shore, reduced the hydraulic gradient towards the river, raised the groundwater table in the river banks and the western part of the Viiankiaapa mire, and increased groundwater discharge in the mire. The groundwater flow models and the stable isotopic composition of water indicate that the constructed dam changed the groundwater flow directions close to dam. The ecological effects of regulation were mixed: the studied flood-dependent plant species declined due to the reduction in floods after regulation. Conversely, the occurrence of Hamatocaulis vernicosus and Hamatocaulis lapponicus appears to be related to the high water table and groundwater discharge areas in the mire, suggesting suitable habitat for these species may have expanded after the regulation.