scholarly journals Simulation of Groundwater Flow in Fractured-Karst Aquifer with a Coupled Model in Maling Reservoir, China

2021 ◽  
Vol 11 (4) ◽  
pp. 1888
Author(s):  
Jinbang Cai ◽  
Yue Su ◽  
Huan Shen ◽  
Yong Huang
Keyword(s):  
Groundwater Flow ◽  
Water Level ◽  
Karst Aquifer ◽  
Coupled Model ◽  
Geometrical Parameters ◽  
Underground Powerhouse ◽  
Groundwater Levels ◽  
Seepage Control ◽  
Fractured Medium ◽  
Karst Systems

A coupled model has been developed to simulate groundwater flow in fractured karst systems according to the complex geological and karst hydrogeological conditions of the dam site, where a 3D mathematical model based on Boussinesq equation was used to describe the movement of groundwater flow in fractured medium, and a 1D conduit model for karst medium. The model was solved with the continuous hydraulic heads at the common boundaries. The hydraulic conductivities of karst medium were determined by geometrical parameters and flux of pipes. Furthermore, the permeability parameters for fractured medium were calibrated by the measured and calculated groundwater levels. The calibrated model was employed to predict the variation of groundwater flow field and leakage from the karst pipes and underground powerhouse during the reservoir operation. The simulated results showed that the groundwater level of the powerhouse had decreased by about 2–5 m. The water level of conveyance pipeline had risen by 10–20 m, and the water level on both banks had risen by 15–25 m. The leakage of karst conduits for impervious failure was larger than that for normal seepage control. In addition, the leakage of the powerhouse was estimated to be about 1000–3000 m3/d, and the seepage control of karst pipes had little influence on the leakage of underground powerhouse.

Borehole-based study of CO2-rich air transport in the vadose zone of a Mediterranean karst system (Malaga, southern Spain)

2020 ◽  
Author(s):  
Lucía Ojeda ◽  
José Benavente ◽  
Iñaki Vadillo ◽  
Cristina Liñán ◽  
Enrique P. Sanchez-Cañete
Keyword(s):  
Vadose Zone ◽  
Karst Aquifer ◽  
Field Measurements ◽  
Temporal Variations ◽  
Groundwater Levels ◽  
Sources And Sinks ◽  
Global Carbon Budget ◽  
Vertical Heterogeneity ◽  
Test Linking ◽  
Karst Systems

<p>The characterization of CO<sub>2 </sub>transport, and other C compounds (CH<sub>4</sub>, DIC, organic matter, etc.), in the vadose zone of a karst aquifer is key in order to quantify sources and sinks of carbon. In karst environments, most of the studies are focused on the dynamics of CO<sub>2</sub> in caves, but only a few studies are related to field measurements of the CO<sub>2</sub> content in boreholes, which provides direct insights about the vadose zone. Located at the east of the Nerja Cave (Malaga, Andalusia), one of the most important tourist caves in Spain, the vadose zone was accessed by 9 boreholes drilled into the vadose zone of a Triassic carbonate aquifer, with depths ranging between 15 and 30 m. The karst network in the study area is characterized by a great vertical heterogeneity, with significant cavities and voids at specific intervals. Groundwater levels at different altitudes are a consequence of this heterogeneity. Similarly, CO<sub>2</sub> distribution and transport are clearly determined by the complex karst network.</p><p>Our study aims to identify significant horizontal gradients of CO<sub>2</sub> in the karst vadose air, both spatial and temporally. We present monthly measurements of CO<sub>2</sub> concentration, relative humidity, air temperature and <sup>222</sup>Rn inside boreholes. In addition, we present CO<sub>2</sub> results from an 18 hours-atmospheric air injection test. Linking them to the geophysical knowledge of voids in the study area, the results allow us to identify lateral fluxes of CO<sub>2</sub>-rich air in the vadose zone and how these fluxes are favoured by the incidence of the main karst discontinuity orientations. We observe different ventilation patterns:  in spring the vadose air seems to be stored in specific orientations, while in summer there is a lower convective ventilation. The results contribute to explain the temporal variations of the chemical composition of recharge water in karst systems, as well as to support studies on the global carbon budget.</p>

Geophysical measurements in an abandoned old railway tunnel located in a karst area

2021 ◽  
Author(s):  
Enzo Rizzo ◽  
Luigi Capozzoli ◽  
Gregory De Martino ◽  
Giacomo Fornasari ◽  
Valeria Giampaolo
Keyword(s):  
Karst Aquifer ◽  
Geophysical Methods ◽  
Water Reservoir ◽  
Test Site ◽  
Point Of View ◽  
Karst Area ◽  
Fluid Circulation ◽  
Railway Tunnel ◽  
Interdisciplinary Field ◽  
Karst Systems

<p>Carbonate aquifers in karst systems are very important water reservoir and are recognized as the most difficult to characterize. The purpose of this article is to present a project aimed to understand the circulation of fluids in carbonate reservoirs through innovative hydrogeophysical methodologies both in the laboratory and in the field. The test site is located in the Castel di Lepre karst system, which is disposed in the Mezo-Cenozoic carbonate substratum of the Monti della Maddalena ridge (Southern Appenines). In the karst area are located several caves, but the presence of an artificial tunnel (disused railway tunnel) could give the opportunity to characterize the whole area and the fluid circulation by multisensors geophysical sensors installed inside the karst aquifer. This natural laboratory permits to define an Applied Geophysics strategy developing several main topics from an engineering to hydrogeological point of view. Firstly, the geophysical investigations conducted, without altering the structure and in a fast manner, obtains important information concerning the construction of the tunnel, and the interaction between the infrastructure and surrounding rock, in that area that we define infrastructural critical zone. The study conducted aims to highlight the potential and any limitations of the use of geophysical techniques applied to infrastructures, emphasizing the emerging role of urban geophysics for the importance and topicality of its contents as well as the important innovations that the use of these techniques they can contribute to the hazardous processes. Secondly, the geophysical methods are used as a tool to characterize the fluid circulation by hydrogeophysal sensors installed inside the karst aquifer. The hydrogeophysics arose as an interdisciplinary field that focuses on the improved understanding of hydrological processes through geophysical observation. These approaches aimed at mitigating the detrimental effects of environmental problems.</p>

scholarly journals Improved representation of groundwater at a regional scale – coupling of mesocale Hydrologic Model (mHM) with OpeneGeoSys (OGS)

2017 ◽  
Author(s):  
Miao Jing ◽  
Falk Heße ◽  
Wenqing Wang ◽  
Thomas Fischer ◽  
Marc Walther ◽  
...  
Keyword(s):  
Time Series ◽  
Groundwater Flow ◽  
Groundwater Recharge ◽  
Large Scale ◽  
Groundwater Modeling ◽  
Coupled Model ◽  
Hydrologic Model ◽  
Source Modeling ◽  
Prediction Ability ◽  
Groundwater Head

Abstract. Most of the current large scale hydrological models do not contain a physically-based groundwater flow component. The main difficulties in large-scale groundwater modeling include the efficient representation of unsaturated zone flow, the characterization of dynamic groundwater-surface water interaction and the numerical stability while preserving complex physical processes and high resolution. To address these problems, we propose a highly-scalable coupled hydrologic and groundwater model (mHM#OGS) based on the integration of two open-source modeling codes: the mesoscale hydrologic Model (mHM) and the finite element simulator OpenGeoSys (OGS). mHM#OGS is coupled using a boundary condition-based coupling scheme that dynamically links the surface and subsurface parts. Nested time stepping allows smaller time steps for typically faster surface runoff routing in mHM and larger time steps for slower subsurface flow in OGS. mHM#OGS features the coupling interface which can transfer the groundwater recharge and river baseflow rate between mHM and OpenGeoSys. Verification of the coupled model was conducted using the time-series of observed streamflow and groundwater levels. Moreover, we force the transient model using groundwater recharge in two scenarios: (1) spatially variable recharge based on the mHM simulations, and (2) spatially homogeneous groundwater recharge. The modeling result in first scenario has a slightly higher correlation with groundwater head time-series, which further validates the plausibility of spatial groundwater recharge distribution calculated by mHM in the mesocale. The statistical analysis of model predictions shows a promising prediction ability of the model. The offline coupling method implemented here can reproduce reasonable groundwater head time series while keep a desired level of detail in the subsurface model structure with little surplus in computational cost. Our exemplary calculations show that the coupled model mHM#OGS can be a valuable tool to assess the effects of variability in land surface heterogeneity, meteorological, topographical forces and geological zonation on the groundwater flow dynamics.

scholarly journals Is hydrotectonics influencing the thermal spring in Eisensteinhöhle (Bad Fischau, Lower Austria)?

2019 ◽  
Vol 112 (2) ◽  
pp. 166-181
Author(s):  
Jonas Hardege ◽  
Lukas Plan ◽  
Gerhard Winkler ◽  
Bernhard Grasemann ◽  
Ivo Baroň
Keyword(s):  
Water Temperature ◽  
Water Level ◽  
Pumping Test ◽  
Normal Faults ◽  
Central Basin ◽  
Sandy Bottom ◽  
Vienna Basin ◽  
High Resolution Data ◽  
Western Margin ◽  
Groundwater Levels

AbstractEisensteinhöhle is a 2 km long crevice cave that is significantly overprinted by hydrothermal karst processes. It was opened during quarrying in the Fischauer Vorberge, at the western margin of the Vienna Basin. This pull-apart basin cuts the eastern foothills of the Alps and is formed by a major NE-SW striking, sinistral transform fault. The western margin consists of NNE-SSW striking normal faults creating paths for thermal water to rise from the central basin. The deepest part of the cave, 73 m below the entrance, hosts a pond with 14.6 ±0.2 °C warm water that occasionally acts as a spring. The water level and temperature fluctuate and at a certain level, water visibly discharges into a nearby narrow fissure. As sporadic observations of the water level since 1992 gave no obvious connection to precipitation events, the connection to an aquifer and the origin of the water remained unknown. A pumping test, conducted on 13/7/2016, yielded a volume of the spring/pool of about 2.8 m3 that is fed by a very small inlet at the sandy bottom. At the time of the pumping test, the discharge was only 4.5 l/h but during previous overflow events, discharge values of up to 289 l/h were recorded.Water temperature and hydrochemistry hint towards a mixture of an old thermal component and a young meteoric component. During continuous monitoring of water level and temperature from October 2015 until November 2018, the water level was almost stable with few periods of high level (almost at overflow) that lasted for about 3 to 4 weeks each. The water temperature increased during most high stands and is positively correlated with the water level. Correlation of the high-resolution data on water level and temperature fluctuations with precipitation measurements at the nearest meteorological stations show a relation of water level to certain rainfall events and the sporadically taken long time records show a correlation with annual precipitation sums. Long-term observations also indicate a connection to groundwater levels in the Vienna Basin with a delay of about 8 weeks in Bad Fischau. In July 2017, the water level dropped suddenly and then recovered simultaneously in the time of several weak earthquakes in the vicinity. The data suggest that the spring in Eisensteinhöhle is influenced by precipitation. For one seismic event, there is a correlation with unusual water level changes at Eisensteinhöhle, but the rareness of earthquakes demands for a longer time series to confirm this observation.

scholarly journals Analysis of Water Cycle in Weizhou Island of Beihai City, Guangxi Province, Part II: Study On Groundwater Exploitation Plan

2018 ◽  
Vol 246 ◽  
pp. 02047
Author(s):  
Shunfu Zhang ◽  
Changjun Liu ◽  
Chuanke Li ◽  
Sili Long ◽  
Jian Zhou ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
Ground Water ◽  
Seawater Intrusion ◽  
Groundwater Level ◽  
Water Cycle ◽  
Variable Density ◽  
Analysis Model ◽  
Guangxi Province ◽  
Groundwater Exploitation ◽  
Groundwater Levels

To relieve the drop of groundwater and seawater intrusion in Weizhou Island caused by overexploitation, the analysis model of precipitation-runoff and variable-density groundwater flow in Weizhou Island was established and the model’s parameter identification results were used to investigate groundwater level and seawater/freshwater interface changes under different groundwater exploitation plans. Thereafter, a rational groundwater exploitation plan could be made to prevent the lowering of groundwater levels caused by ground water overexploitation and ecological deterioration caused by seawater intrusion. This could help accelerating the recovery of ground water and maintaining ecological system.

scholarly journals A numerical geotechnical model for computing soil slides at banks of water reservoirs

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Nils Reidar B. Olsen ◽  
Stefan Haun
Keyword(s):  
Numerical Model ◽  
Water Level ◽  
Stokes Equations ◽  
Limit Equilibrium ◽  
Three Dimensional ◽  
Field Measurements ◽  
Navier Stokes ◽  
Adaptive Grids ◽  
Groundwater Levels ◽  
Before And After

AbstractSoil slides can occur when the water level in a lake or a reservoir is lowered. This may take place in situations when a reservoir is flushed to remove sediments. The current study describes a three-dimensional numerical model used for the simulation of reservoir flushing that includes the slide movements. The geotechnical failure algorithms start with modelling the groundwater levels at the banks of the reservoir. A limit equilibrium approach is further used to find the location of the slides. The actual movement of the sediments is computed by assuming the soil to be a viscous liquid and by solving the Navier–Stokes equations. The resulting bed elevation changes from the slides are computed in adaptive grids that change as a function of water level, bed erosion and slide movements. The numerical model is tested on the Bodendorf reservoir in Austria, where field measurements are available of the bank elevations before and after a flushing operation. The results from the numerical simulations are compared with these observations. A parameter test shows that the results are very sensitive to the cohesion and less sensitive to the E and G modules of the soil.

scholarly journals Taking into Account both Explicit Conduits and the Unsaturated Zone in Karst Reservoir Hybrid Models: Impact on the Outlet Hydrograph

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3221
Author(s):  
Lucie Dal Soglio ◽  
Charles Danquigny ◽  
Naomi Mazzilli ◽  
Christophe Emblanch ◽  
Gérard Massonnat
Keyword(s):  
Unsaturated Zone ◽  
Numerical Models ◽  
Karst Aquifer ◽  
Hybrid Models ◽  
Model Parameters ◽  
Transit Times ◽  
The Matrix ◽  
Karst Reservoir ◽  
Karst Systems ◽  
The One

The main outlets of karst systems are springs, the hydrographs of which are largely affected by flow processes in the unsaturated zone. These processes differ between the epikarst and transmission zone on the one hand and the matrix and conduit on the other hand. However, numerical models rarely consider the unsaturated zone, let alone distinguishing its subsystems. Likewise, few models represent conduits through a second medium, and even fewer do this explicitly with discrete features. This paper focuses on the interest of hybrid models that take into account both unsaturated subsystems and discrete conduits to simulate the reservoir-scale response, especially the outlet hydrograph. In a synthetic karst aquifer model, we performed simulations for several parameter sets and showed the ability of hybrid models to simulate the overall response of complex karst aquifers. Varying parameters affect the pathway distribution and transit times, which results in a large variety of hydrograph shapes. We propose a classification of hydrographs and selected characteristics, which proves useful for analysing the results. The relationships between model parameters and hydrograph characteristics are not all linear; some of them have local extrema or threshold limits. The numerous simulations help to assess the sensitivity of hydrograph characteristics to the different parameters and, conversely, to identify the key parameters which can be manipulated to enhance the modelling of field cases.

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