Phreatic Level Research Articles

The condition status index for doline lakes in urban areas

Karst represents approximately 15% of the planet’s surface, hundreds of millions of people live on and rely on these aquifers for water supply and agricultural irrigation. In karstic landscapes, groundwater is exposed in sinkholes, inundated caves, and artesian wells, which are two-way communication spots. When the phreatic level is exposed, the groundwater can change substantially as a result of anthropogenic impacts, modifying the water quality and the environmental integrity by incoming excess nutrients, contaminants, pathogens, and other hazardous substances such as metals and microplastics. In this paper, we develop and test a multimetric index to evaluate the condition status of dolines located within urban areas, including seven indicators: trophic index, fecal bacteria, fecal viruses, microplastics, heavy metals, zooplankton biodiversity, and fish biodiversity. Lastly, we made a proof of concept for the index in the dolines on the island of Cozumel (Mexico), resulting in evaluations from fair to good. The index is powerful due to its sensitivity to pathogens and exotic invasive species. This additive weighted index allows to assess the condition status of dolines in urban areas anywhere in the world; if required, modifications are possible.

Modeling the influence of forest vegetation and climate change on the long-term performance of a cover with capillary barrier effects used to control acid mine drainage: the Lorraine case study

ABSTRACT The Lorraine mine site in Témiscamingue region (Québec, Canada) was reclaimed with a cover with capillary barrier effects (CCBE) to limit acid mine drainage generation. The main objective of this study is to predict the long-term hydrogeological behaviour of the CCBE at Lorraine site, including the influence of vegetation and climate change (CC). Numerical simulations showed that performance of the CCBE is: (1) not affected by forest vegetation and CC in the saturated zone in the north of the Lorraine site and (2) more sensitive to vegetation in the unsaturated zone in the south where the phreatic level is low.

Loading effect of phreatic level variations induced by river tide on groundwater head fluctuations in tidal river aquifer systems

The unconfined groundwater level variations caused by the river tide can impact the fluctuation of the groundwater head in the underlying confined aquifer by loading effect. In this study, we proposed a mathematical model and provided an analytical solution for a confined aquifer system considering the loading effect when the aquifer system is eroded by the tidal river to varying extents. The results demonstrated that the loading effect tends to amplify the amplitude of the tide-induced head fluctuation while reduce its phase shift in the confined aquifer. These effects are more significant with a larger tidal loading efficiency, a wider tidal river, and a smaller tidal propagation parameter of the unconfined aquifer. The analytical solution was validated by the observed groundwater level fluctuations from a groundwater level monitoring well near a tidal river in the Peral River Delta of China, and provided reliable estimations of aquifer parameters in the region.

Groundwater Hydraulics in Increased Spring Discharge following Earthquakes: Some Applications and Considerations

Earthquakes often entail alterations in the groundwater flow regime, in the phreatic level, surges and losses of springs, and the discharge in brooks. A variety of theoretical approaches attempt to elucidate the post-earthquake effects on spring discharge. This study adopts a conceptual approach, primarily presenting diverse methods to estimate water released by earthquakes involving calculations of discharge surpluses in springs. This study delves into refined techniques rooted in groundwater hydraulics, displaying applications of analytical and simulation methodologies to quantify earthquake-induced groundwater discharge in springs. This research investigates springs as natural indicators and applies mathematical precipitation–runoff models, particularly the CREC model, to simulate hydrographs in post-earthquake scenarios. We apply analytical procedures or mathematical simulation techniques employed in groundwater hydraulics for natural aquifer recharge calculations. Firstly, we briefly describe the methods based on the analysis of depletion curves of hydrographs in spring discharge. Additionally, specific mathematical rainfall–runoff models used to simulate hydrographs of karstic springs, along with derived analytical approximations, are adapted for this scenario. These hydraulic calculations involve the depletion coefficient and hydrodynamic volumes of aquifers, parameters that reveal certain aspects of the relation between groundwater and earthquakes. Three main features are: (a) Acknowledging faults as the primary geological structures in transmitting pore pressures due to earthquakes. Thus, for large and deep faults, which connect the ground surface with the Earth’s crust bottom—where earthquakes trigger—the depletion coefficient, α, usually reaches high values (α = 0.1 days−1). Therefore, these faults become more sensitive to pore pressure than other lithologies. (b) Elucidating the mechanisms of permeability enhancement caused by earthquakes. (c) Highlighting the substantial volumes in motion within the Earth’s interior, which, for instance, could constitute a significant source for the origin of mineral deposits. Mathematical calculations enable the determination of the volume of mobilized water that can be discharged by gravity in each earthquake. This, along with its recurrence, justifies the substantial mineralization volumes.

Groundwater Abstraction has Caused Extensive Ecological Damage to the Doñana World Heritage Site, Spain

Acreman et al. (Wetlands 42:63, 2022) reviewed evidence for ecological damage to the Doñana wetlands (UNESCO World Heritage Site [WHS] and Ramsar site), Spain, associated with intensification of groundwater use, particularly for agriculture. Acreman et al. presented a multistep methodology for evidence-based risk assessment that involves identification of conservation issues, and a systematic review of scientific evidence for ecological damage and its causes. However, they involved few local scientists, used a questionable methodology in stakeholder selection and involvement, used a flawed conceptual framework, and an incomplete literature review. We propose improvements to their methodology. They overlooked or misinterpreted key evidence, and underestimated the impacts that abstraction for irrigation for red fruits (mainly strawberries), rice and other crops has had on Doñana and its biodiversity. They reported groundwater level depletion of up to 10 m in the deep aquifer, but wrongly concluded that there is no evidence for impacts on the natural marsh ecosystem, the dune ponds or the ecotone. Groundwater drawdowns are actually up to 20 m, and have inverted the formerly ascending vertical hydraulic gradient in discharge areas. Phreatic levels have been lowered from 0.5 to 2 m in some areas. Groundwater abstraction has caused multiple ecological impacts to temporary ponds and marshes in the WHS, as well as to terrestrial vegetation, and should be urgently reduced. Furthermore, Acreman et al. focused on groundwater quantity while overlooking the importance of severe impacts on quality of both surface and groundwater, intimately connected to the use of agrochemicals for irrigated crops.

The Dynamics of Soil Mesofauna Communities in a Tropical Urban Coastal Wetland: Responses to Spatiotemporal Fluctuations in Phreatic Level and Salinity

Coastal wetlands, vital for ecological diversity, have been significantly altered by anthropogenic activities, particularly in the Caribbean. These changes have created a complex mosaic of habitats and physicochemical conditions, further stressed by climate variability and sea-level rise. This study, conducted in Las Cucharillas Natural Reserve, a tropical urban coastal wetland in Puerto Rico, aimed to determine the effects of spatiotemporal variations in phreatic levels and salinity on soil mesofauna assemblages, crucial bio-indicators of environmental change. In 2020 and 2021, soil samples were collected from five diverse habitat types during different hydroperiods. Each sample was taken under four randomly selected plant types and processed using lighted Tullgren–Berlese extractors. Phreatic level and salinity were also measured. A total of 43 families were quantified, underscoring distinct habitat differences, similarities, and overall ecosystem diversity. Moderate correlations between phreatic levels, salinity, and mesofauna richness and abundance were determined. Peak richness and abundance were quantified at shallow (−0.03 to −0.07 m) and slightly moderate (−0.12 to −0.17 m) phreatic levels where oligohaline salinity (>0.5 to 5.0 ppt) prevails. The study highlights the adaptability of mesofauna to environmental shifts and their potential as biosensors for effective coastal wetland management amid climatic and anthropogenic pressures.

The catastrophic effects of groundwater intensive exploitation and Megadrought on aquifers in Central Chile: Global change impact projections in water resources based on groundwater balance modeling

Central Chile is undergoing its most severe drought since 2010, affecting ecosystems, water supply, agriculture, and industrial uses. The government's short-term measures, such as increasing groundwater extraction (by 383 % from 1997 to 2022), are exacerbating the situation, leading to long-term hydrological deterioration. The objective of this research is to establish the main processes driving the water table depth evolution within Central Chile over the period 1979–2023. This is done by conducting groundwater balances on five major hydrological basins of Central Chile. For the Megadrought (MD) period (2010−2022), the groundwater level depths reflect not only the recharge variability but, especially, the forcing trend of groundwater withdrawals: they represent 35 % and 65 %, respectively, of the total phreatic level drawdown. This result underlines the dominant role played by groundwater withdrawals in the current delicate state of Central Chile's groundwater resources, while revealing that drought is a new complex phenomenon to deal with, in the midterm, to revert the current water resource trend in Central Chile. Our study moreover presents the impact of climate change in the basin in the framework of six different groundwater withdrawal scenarios. In the worst case (i.e., RCP8.5), the aquifer recharge decreases 18 % with respect to 1979–1997, which is the period assumed to be unaffected by the impact of MD and withdrawals. Such a reduction may be irrelevant in the dynamics of the aquifer system if the current extraction rate does not change. The estimated recovery time needed to reach aquifer conditions equal to those of the unaffected period is approximately 50 years.

Groundwater sustainability in the Friuli Plain

Groundwater resources in the Friuli Venezia Giulia (FVG) Region (northeast Italy) are an important natural wealth in terms of quantity, quality and ease of supply. This optimal condition, however, has long believed that it allowed an irrational and uncontrolled exploitation that inevitably produced tangible consequences on the water resources availability.The goal of the present research is the evaluation of the sustainable use of the groundwater in the Friuli Venezia Giulia Region aimed at providing guide-lines for its rational use. The study area belongs to the hydrogeological basin of the Friuli Plain and includes part of Veneto Region and Slovenia. The plain area is divided in two parts: the High Plain (HP) characterized by a phreatic aquifer and the Low Plain (LP) where eleven confined aquifer systems were identified. The two physiographic zones are separated by the spring belt. In order to evaluate the groundwater avaliability, a 3D model of the Low Friuli Plain aquifer systems was realized using Rockworks R14 software, starting from 603 lithostratigraphic wells data. Isobath and isopach maps were elaborated using kriging geostatistical method. Precipitation, evapotranspiration, runoff and infiltration were calculated to evaluate the inflow and outflow groundwater budget terms (109 rainfall and 46 thermometric stations, time series 1979-2008). To better define the river influences and the outflows at sea, a series of recent surveys on river discharges and surface withdrawals were considered. To obtain the water-budget in non-natural conditions, as the currents, were taken into account the groundwater withdrawals that were evaluated for each type of use and for each aquifer systems, starting from 2 geodatabases: one for the domestic uses (50101 estimated wells) and one for the industrial, agricultural, fish breeding, hygienic, geothermal and other minor uses (7594 wells). Well withdrawals amount were evaluated on annual base for recent periods and expressed as m3/s. The total current estimated groundwater withdrawals reach 62.4 m3/s, of which 41.1 m3/s from the confined aquifer systems in the LP area. More than 52% of the withdrawals are due to the domestic wells. For the water-budget, the studied territory was considered a “semi-closed box” in which groundwater sharings with the neighboring areas are not relevant and where the recharge is mainly due to the influent character of the river, infiltration, rainfall and irrigation practices. As result, the waterbudget for the confined LP is equal to +2.6 m3/s representing the accuracy, fairly acceptable for the scale of the research. Withdrawal entity, spring belt discharge, phreatic levels and confined aquifer’s pressure are closely interdependent and in dynamic equilibrium. The sustainability comes from the consistency and ratio between recharge and withdrawals. The confined aquifer withdrawals in the LP represent the 23.1% of the groundwater recharge coming from the HP and the 30.6% of the spring belt discharge. Seen that this last one can not further decrease, unless loss of important ecosystems, is likely to think that the present situation can be defined of limit equilibrium.

Numerical stability analysis and geotechnical investigation of landslide prone area (the case of Gechi district, Western Ethiopia)

The primary route linking Tobba, Gechi and Beddele has experienced landslides at three locations, causing significant disruption to traffic. The juniper trees and electric poles have suffered damage, and the extension lines are at risk. This investigation aims to identify the geotechnical conditions, soil type, and their role in landslide initiation, slope stability analysis, and measures to reduce the risk of landslides. The study employed fieldwork, laboratory analysis, and software analysis. The fieldwork involved measuring the slope geometry and landslide magnitude, as well as geophysical resistivity to determine the soil type and thickness of the weak zone. Soil samples were taken and tested for grain size analysis, Atterberg limit, water content, unit weight of soil, specific gravity, and shear strength parameters, following ASTM procedures. Plaxis v 8.6 software was used to supplement the slope stability analysis. The results indicate that the soil in the study area is classified as MH- elastic silt and elastic silt with sand (S1BH3 and S2BH1) behaving as sand. The fine-grained soil constitutes ≥50% of the soil, which significantly influences the soil properties. The numerical value of the factor of safety (FOS) from slope stability analysis decreases as the phreatic level increases. Electrical resistivity profiling indicated that there is a change in soil matrix and grainsize distribution. The dry unit weight varies from 6.28KN/m3 to 43.23KN/m3 and the slope angle varies from 14.09° to 14.62°. The cohesion of the soil varies from 40.71KN/m2 to 67.02KN/m2 and the angle of internal friction varies from 15.12° to 26.62°. The landslides were triggered by heavy rainfall, and the primary factors affecting slope stability are soil type and characteristics, surface and groundwater, and slope steepness. To maintain the slope's stability, it is recommended to modify the slope geometry, construct sheet piles and retaining walls, provide adequate drainage structures, and afforest the area with long-rooted grass and trees.

Environmental Assessment of Soil and Groundwater Pollution by BTEX Leaching in Valencia Region (Spain)

The impact of hydrocarbon spills in the unsaturated zone is a significant environmental concern, particularly in locations where contamination arises from leaks in underground fuel storage tanks (USTs). This paper presents the outcomes achieved through the utilization of VLEACH, a finite-difference numerical model, to assess the concentrations of organic contaminants in the solid, liquid, and gas phases within the vadose zone. Additionally, it evaluates the mass transfer of pollutants to the aquifer as part of an environmental assessment for the placement of a forthcoming service station. The study encompasses an analysis of 18 scenarios under realistic conditions based on actual field data. These scenarios were constructed, taking into account various factors, including the nature of the leak (one-time or permanent), the depth of the phreatic level, and the soil conditions and properties. The results highlight the potential environmental consequences of a permanent leak as compared to those resulting from a specific accident. The findings further emphasize the substantial influence of soil moisture on transport phenomena within the vadose zone. Variations in soil moisture significantly alter hydraulic conductivity, impact magnitudes, transport velocities, and even the predominant transport mechanism. Consequently, precise delineation of soil moisture becomes a crucial parameter in such simulations. Additionally, it has been observed that each component of BTEX (benzene, toluene, ethylbenzene, and xylene) experiences varying transport velocities through the vadose zone. Benzene, having a greater propensity to concentrate in the liquid and gas phases, exhibits the swiftest movement through the vadose zone. The detection of benzene in aquifers can serve as an indicator of the potential future arrival of the remaining BTEX compounds.

Spatio-temporal modeling of groundwater quality deterioration and resource depletion

In Hydrogeology, the analysis of groundwater features is based on multiple data related to correlated variables recorded over a spatio-temporal domain. Thus, multivariate geostatistical tools are fundamental for assessment of the data variability in space and time, as well as for parametric and nonparametric modeling. In this work, three key hydrological indicators of the quality of groundwater—sodium adsorption ratio, chloride and electrical conductivity—as well as the phreatic level, in the unconfined aquifer of the central area of Veneto Region (Italy) are investigated and modeled for prediction purposes. By using a new geostatistical approach, probability maps of groundwater resource deterioration are computed, and some areas where the aquifer needs strong attention are identified in the north-east part of the study region. The proposed analytical methodology and the findings can support policy makers in planning actions aimed at sustainable water management, which should enable better monitoring of groundwater used for drinking and also ensure high quality of water for irrigation purposes.

Winds of opportunity: The effects of wind on intertidal flat accretion

Intertidal ecosystems are threatened by sea level rise and anthropogenic pressures. Understanding the processes controlling the morphodynamic developments of tidal flats is crucial for sustainable management of these systems. Analysis of three extensive fieldwork campaigns carried out on two adjacent mudflats fringing the Dutch Western Wadden Sea (from 2016 to 2018) provides important new insights into the conditions controlling a permanent increase of tidal flat elevation (‘accretion’), in which the wind and consolidation processes play a pivotal role. Sediment temporarily settles (‘deposition’) on the flats during a period of high suspended sediment availability and water level setup (often following a storm). A tidal flat accretes when a new layer of sediment over-consolidates: a state in which the bed strength is much larger than it would attain during inundated conditions, due to high stresses experienced during prolonged drying. This happens when a phase of sediment deposition is followed by a sufficiently long period with a low ambient water table (phreatic level) and aerial exposure. The chronological order of sediment deposition and over-consolidation provides a window of opportunity for tidal flat accretion. Such a window of opportunity depends on the hydrodynamic forcing (tides, waves, wind), on the consolidation state of the bed, and on sediment availability. Wind plays a crucial role in creating the conditions for tidal flat accretion because the wind direction influences the duration of a low water table and aerial exposure and therefore (over-)consolidation rates, which we refer to as the ‘winds of opportunity’. An abundance of sediment may even limit tidal flat accretion, because large deposition rates substantially increase consolidation timescales.

Study on the relationship between phreatic level and water quality: a case study of city in northwest China

Phreatic is an important water resource for human survival and development. With the process of urbanization, diving in many areas has been polluted to varying degrees. In order to find out the existing relationship between phreatic level and water quality, in this study, 53 Wells in the main urban area of Xi’an in 2017 were selected to map and analyze the submersible water level, and the improved fuzzy comprehensive evaluation was used to evaluate the submersible water quality. The results show that the change of phreatic level is closely related to the fluctuation of terrain. The improved fuzzy comprehensive evaluation method can well reflect the phreatic quality in the study area, and it is universal. There is a linear relationship between phreatic level and water quality. Due to the flow in phreatic water, the polluted phreatic in the upstream will pollute it in the downstream. This is also the reason why the water quality along the Weihe River is poor. This study has positive significance for the good development of phreatic protection and the construction of human life in the study area.

Image based probabilistic slope stability analysis of soil layer interface fluctuations with Brownian bridges

Accurate interpretation of stratigraphic profiles, the phreatic surface and the spatial variability of geomaterials are essential to produce representative behaviour of geomechanical systems through numerical simulations. When considering slope stability, variations in soil layer boundaries and the phreatic surface may result in misleading metrics such as the Factor of Safety (FoS) and the Probability of Failure (PoF). This paper presents an image-based technique for generating continuous stratigraphic profiles, including random fluctuations based on Brownian motion. Brownian bridges are used to produce random walks between known points on both soil layer boundaries and the phreatic level that overlap with the slope profile image. Quadtree decomposition is used to discretise the stratigraphy and the phreatic level through an automatic process using generated digital images for mesh generation while also integrating material properties. The Scaled Boundary Finite Element (SBFEM) is used to analyse the slope stability problem. Images based on random walks along an unknown stratigraphic material boundary and the phreatic surface are randomly generated and have many random possibilities, which are used to undertake probabilistic analysis to obtain PoF. This process is complex when using numerical methods, such as the Finite Element Method, as it requires mesh generation from different slope profiles with alternating material interfaces at each probabilistic instance. When the Scaled Boundary Finite Element Method is applied, probabilistic numerical analyses can be fully automated for randomly generated material interfaces. The feasibility of the proposed method is illustrated through several cases of a slope with multiple material layers, in addition to a slope incorporating a Brownian bridge phreatic surface formulation.

Numerical Simulation and Characterization of the Hydromechanical Alterations at the Zafarraya Fault Due to the 1884 Andalusia Earthquake (Spain)

The 1884 Andalusia Earthquake, with an estimated magnitude between 6.2 and 6.7, is one of the most destructive events that shook the Iberian Peninsula, causing around 1200 casualties. According to paleoseismology studies and intensity maps, the earthquake source relates to the normal Ventas de Zafarraya Fault (Granada, Spain). Diverse studies registered and later analyzed hydrological effects, such as landslides, rockfalls, soil liquefaction, all-around surge and loss of springs, alterations in the phreatic level, discharge in springs and brooks and well levels, along with changes in physical and chemical parameters of groundwater. Further insight into these phenomena found an interplay between hydromechanical processes and crust surface deformations, conditions, and properties. This study focuses on analyzing and simulating the features involved in the major 1884 event and aims at elucidating the mechanisms concerning the mentioned effects. This ex-post analysis builds on the qualitative effects and visible alterations registered by historical studies. It encompasses conceptual geological and kinematic models and a 2D finite element simulation to account for the processes undergone by the Zafarraya Fault. The study focuses on the variability of hydromechanical features and the time evolution of the ground pore–pressure distribution in both the preseismic and coseismic stages, matching some of the shreds of evidence found by field studies. This procedure has helped to shed light on the causal mechanisms and better understand some parameters of this historical earthquake, such as its hypocenter and magnitude. This methodology can be applied to other events registered in the National Catalogues of Earthquakes to achieve a deeper insight, further knowledge, and a better understanding of past earthquakes.

The positive history of an error. Modelling the heave of a nuclear power station

The paper describes two different procedures to explain and to model the observed heave of a nuclear power plant founded on an expansive unsaturated claystone. In the initial model developed, the claystone was represented by a double structure (micro-macro) expansive clay. Field swelling records were accurately reproduced and the model was used to predict the long-term (40 yr) expected vertical displacements. Years after, it was realized that a more consistent explanation for the observed heave was the precipitation of gypsum crystals in discontinuities. The alternative physical phenomenon led to a re-formulation of an appropriate model, which is described in the paper. The key aspect of the long-term heave was the presence of anhydrite in the claystone mineralogical composition. The paper explains the physics of crystal growth that was triggered by the construction of the power station, the large excavation performed to locate the plant buildings and by the presence of a phreatic level, that was a consequence of the geometry of excavations. The new model, substantially more complex than the first one, is also able to reproduce available laboratory long-term swelling tests and field observations. It is hopefully a more reliable model to predict the long-term behaviour. The positive part of this history is that the initial model inspired the development of successful elastoplastic constitutive models for expansive clays.

Visualization study on preferential flow in highly saturated and super hydrophilic porous media by combining dye tracking and infrared imaging

• New method to track finger flow in highly saturated superhydrophilic porous media. • Preferential flow recurrence was observed at high saturation. • The preferential flow was found to impair desalination efficiency. • The temperature distribution was controlled by preferential flow. Air-gap diffusion distillation (AGDD) is a practical desalination technique. The highly saturated super hydrophilic porous medium as its evaporation surface has a decisive influence on the desalination efficiency of AGDD. In experiments, we found preferential flow in porous media. However, the preferential flow in highly saturated super hydrophilic porous media has not been studied, and the effect of preferential paths on evaporation from porous media surfaces remains poorly understood. The method of combining dye tracking and infrared imaging was used to visualize the process of thermal seepage in highly saturated super hydrophilic porous media. Under the condition of uniform and continuous liquid supply on the upper surface, the preferential flow characteristics of hot stream seepage in porous media are tracked; Point source infiltration experiments were carried out at room temperature to compare the difference between preferential flow in super hydrophilic porous media and general soil (sand). The experimental results of thermal seepage showed that the preferential flow greatly influences the uneven temperature distribution of the porous media, which directly impairs the desalination efficiency of AGDD. According to the coefficient of variation (CV), the preferential flow development process can be divided into three stages: stable development, exponential development, and high-speed growth. As the seepage flow is stabilized, the influence of preferential flow on the flow field and temperature field still exists and is affected by these three stages. Preferential flow characteristics were also captured in the saturated capillary rise zone at the bottom of the porous medium (below the phreatic level). The point source infiltration experiment found that the preferential flow in superhydrophilic porous medium will reappear at high saturation, which is completely different from the soil (sand) studied by previous studies. In addition, the effects of inlet temperature, flow rate, thickness, and hydrophilic, hygroscopicity on preferential flow were discussed. Increasing the flow rate and inlet temperature and reducing the thickness of the porous media can weaken the influence of preferential flow on the temperature field. But increasing the temperature only superficially weakens the preferential flow. Increasing hydrophilicity and hygroscopicity can also reduce the preferential flow.

Unified modelling framework of flowslide triggering and runout

Hydro-mechanical forcing, including sediment deposition, seismic loading, rainfall events and phreatic level rise, can alter the pore water pressure regime and trigger ground failure. In loose sands, such phenomena can manifest with rapid downslope movements displaying signatures of liquefaction and commonly referred to as ‘flowslides’. These can have catastrophic outcomes, yet the use of constitutive models for soils able to quantify the likelihood of liquefaction is usually restricted to triggering analyses, while the quantification of runout distance and velocity tends to be conducted through computationally expensive models based on rheological laws for fluids. To enable a seamless transition from the triggering to the runout stage, in this paper, a spatially condensed modelling framework of low computational cost is proposed, which allows for straightforward use of soil constitutive models in the analysis of the entire life cycle of a flowslide. The proposed framework couples the dynamic motion of a landslide mass with the pore fluid transients taking place within a pre-defined liquefiable zone. The constitutive law modulates the feedback between pore fluid diffusion and landslide movement, encompassing elastoplastic and viscoplastic soil models within the same formulation. Simulations show that partial drainage in the liquefiable zone has considerable effects on the triggering stresses initiating a flowslide. Specifically, the results imply that liquefaction risks are sharply suppressed when the ratio between the characteristic times of loading and pore pressure diffusion falls above a critical threshold influenced by the inelastic deformation response of the soil. Furthermore, it is shown that all the dynamics of flowslide propagation are dominated by the ratio between the characteristic timescales related to fluid consolidation, wave propagation and soil reaction time (i.e. soil viscosity). Although viscosity is not necessary to carry out propagation analyses, ignoring it leads to unrealistic estimates of peak velocity and runout distance. As a result, the model predicts that sand viscosity reflecting the emergence of a microscopic inertial regime is required to explain the flowslide propagation characteristics reported in the literature.

Impacts of underground coal mining on phreatic water level variation in arid and semiarid mining areas: a case study from the Yushenfu mining area, China

Impacts of underground coal mining on phreatic water level variation in arid and semiarid mining areas: a case study from the Yushenfu mining area, China

Assessment of Spatial Distribution and Temporal Variations of the Phreatic Groundwater Level Using Geostatistical Modelling: The Case of Oued Souf Valley—Southern East of Algeria

Since the beginning of the 1980s, several regions in the northern Sahara of Algeria have been confronting the rising groundwater. Among all these regions, Oued Souf Valley represented one of the most acute affected by this phenomenon. Due to the natural topography and the insufficient/weakness of water management and miscoordination between different sectors that are represented by intensive exploitation of deep groundwater reservoirs which returns to the shallow aquifer, absence of sewage and drainage network, leakage from drinking water supply system, the groundwater has raised to the surface or near to the surface, affecting the traditional cultural environment and urban areas and degrading all socio-economic aspects of the Oued Souf habitants. To preserve the Oued Souf environment, a vertical drainage system has been constructed. Consequently, in this research, an evaluation of the vertical drainage system performance and its impact on groundwater level stabilization has been performed by mapping the water table of the phreatic groundwater level using geostatistical modeling using ordinary kriging (OK) interpolation method, which has been applied to analyze the spatial and temporal structure of groundwater level fluctuation. Meanwhile, hierarchical cluster analysis (HCA) was applied for grouping the wells based on the groundwater fluctuations for 2008, 2009, 2014, 2016, 2018, and 2021. However, the vertical drainage system reflected a significant decline of groundwater from 2009 to 2018 due to the important drained volumes through it but another rising phenomenon might be threatening the region in the near future and this is what was indicated in the 2021 groundwater level data. Cluster analysis has generated four groups based on their fluctuation means that are increasing from the first group to the fourth group ascendingly. The first cluster grouped the drains that have a shallow depth (average mean of 5.91 mbgl) and declined over the clusters. The clusters are spatially combined with significant separation of the fourth cluster which represents the deepest group (12.89 mbgl). Based on this research, several factors are influencing the stability of the phreatic groundwater level and even the performance of the drainage system, the most important of which is the overexploitation from deep groundwater reservoirs such as complex terminal and continental intercalary (in drinking and irrigation) and even the illegal use of the phreatic groundwater with important quantities for irrigation and illegal industries.