Search

In hydrogeology, equations describing exchange flux in sedimentary systems mainly focus on the geometry of the streambed–aquifer system and parameters. However, groundwater flow in fractured crystalline basement and volcanic rocks, which are mainly characterized by restricted flow, receives little attention in groundwater flow equations, possibly due to a lack of appropriate data. This study develops an analytical equation to estimate groundwater inflow into mine pits in volcanic rock, addressing a significant knowledge gap in the literature. The equation was validated through a case study evaluation at the Nsuta Mine, where it accurately estimated groundwater inflow into the pit. Results indicate that estimated inflow at the current pit floor level (−60 MSL) is 38 710 m3/day, which is close to the actual dewatering rate of 39 794 m3/day (error percentage of 2.8%). The study also projects groundwater inflow at a deeper pit level (−200 MSL) to be 82 400 m3/day with a corresponding flux of 0.331 m/day. [ABSTRACT FROM AUTHOR]

Rainfall–runoff characteristics of mountainous catchments are affected by many factors, such as topography and geology. Traditionally, the effects of geology on rainfall–runoff characteristics have been explained using geology, but the differences in runoff characteristics within the same geological settings have not been examined. These differences can be expressed as differences between the hydrological model parameters. However, the effects of geology on the model calculations have not yet been clarified. Thus, this study aims to clarify the effects of topography and geology on model calculations using an improved HYdrologic CYcle (HYCY) model that considers bedrock infiltration. Runoff observations were conducted for approximately 3 years in 19 catchments at 2 sites located in sedimentary rock and granite mountains. Rainfall was recorded at each site. The observed hydrographs were used to optimise the parameters for each catchment using the least‐squares method. The relationship between parameter m and the soil layer storage was calculated using the optimised parameters, representing the percentage of the area contributing to runoff. Furthermore, these results were compared with observational analysis results. The improved HYCY model accurately represented all 19 runoffs. When the total precipitation in 1 event exceeded 200 mm, parameter m became ~1 and ~0.3–0.4 in sedimentary rock and granitic catchments, respectively, which shows the effect of geology. The effects of topography on the parameters were exhibited in Kc and Kb, which calculated the storm flow from the channels and baseflow hydrographs, respectively. However, the parameter distributions exhibited geological differences, namely in parameter Kh, Kb and m. The parameter Kh calculates the overland flow hydrograph. This implies that geological differences affect the probability of the overland flow generation rate and the recession hydrographs of the overland flow and baseflow. [ABSTRACT FROM AUTHOR]

Various hydrogeological problems like groundwater inflow, water table drawdown, and water pressure redistribution may be encountered in the construction of hydraulic projects. How to accurately predict the occurrence of groundwater inflow and assess the drainage effect during construction are still challenging problems for engineering designers. Taking the Jinzhai pumped storage power station (JPSPS) of China as an example, this paper aims to use different methods to calculate the water inflow rates of an underground powerhouse and evaluate the drainage effect caused by tunnel inflow during construction. The methods consist of the analytical formulas, the site groundwater rating (SGR) method, and the Signorini type variational inequality formulation. The results show that the analytical methods considering stable water table may overestimate the water inflow rates of caverns in drained conditions, whereas the SGR method with available hydro-geological parameters obtains a qualitative hazard assessment in the preliminary phase. The numerical solutions provide more precise and reliable values of groundwater inflow considering complex geological structures and seepage control measures. Moreover, the drainage effects, including a seepage-free surface, pore water pressure redistribution, and hydraulic gradient, have been accurately evaluated using various numerical synthetic cases. Specifically, the faults intersecting on underground caverns and drainage structures significantly change the groundwater flow regime around caverns. This comparative study can not only exactly identify the capabilities of the methods for cavern inflow in drained conditions, but also can comprehensively evaluate the drainage effect during cavern construction. [ABSTRACT FROM AUTHOR]

To mitigate unforeseen incidents, such as key block failure or tunnel collapse during excavation, an appropriate support pattern that correlates with the geological conditions of the rock mass at the tunnel face should be designed. Rock mass evaluations should be conducted through geological face mapping during the construction phase, alongside predictions based on field investigations during the design phase. When marked discrepancies are identified, it is customary to convene an on-site evaluation involving a committee of experts. This study develops a digital tunnel face mapping system that utilises mobile devices to facilitate online evaluations during the construction phase. This system effectively replaces the traditional on-site field evaluation method. Tunnel face mapping can be promptly accomplished using images captured at the excavation face, enabling rapid analysis. In conjunction with the mapping capabilities, the developed system was designed to digitally store geological information, which includes parameters such as rock strength distribution, the spacing and length of discontinuities observed during the mapping process, as well as data pertaining to weathering and the groundwater conditions of those discontinuities. This information was then correlated with the rock mass rating sheet to automate the determination of ratings for each parameter, ultimately leading to a conclusive classification of the rock mass quality. By employing this system for tunnel face mapping and rock quality evaluation, we significantly reduced the discrepancies in the evaluation results that often arise due to the subjective judgement of geologists, as well as human errors that can occur throughout the rating process. [ABSTRACT FROM AUTHOR]

Highly permeable geological structures such as dissolution channels, open fractures, and faults create environmental challenges regard to hydrological and hydrogeological aspects of underground construction, often causing significant groundwater inflow during drilling due to the limitations of empirical and analytical methods. This study aims to identify the geological factors influencing water flow into the tunnel. High-flow zones' geological features have been identified and examined for this purpose. According to the geological complexity of the Nowsud tunnel, presence of different formations with different permeability and karstification have led to a high volume of underground inflow water (up to 4700 L/s) to the tunnel. The Nowsud tunnel faces significant geological and hydrogeological challenges due to its passage through the Ilam formation's LI2 unit, characterized by dissolution channels, faults, and fractures. The highest inflow rate (4700 L/s) occurred in the Hz-9 zone within the Zimkan anticline. The relationship between geological features and groundwater inflow indicates that anticlines are more susceptible to inflow than synclines. Additionally, different types of faults exhibit varying hydraulic effects, with strike-slip faults having the most significant impact on groundwater inflow, thrust faults conducting less water into the tunnel, and inflow through normal faults being negligible compared to the other two types of faults. The novelty of this paper lies in its detailed analysis of geological features influencing groundwater inflow into the Nowsud tunnel, providing empirical data on high-flow zones and differentiating the hydraulic effects of various fault types, which enhances the understanding and prediction of groundwater inflow in underground constructions. [ABSTRACT FROM AUTHOR]

Evaluating groundwater inflow is greatly significant for ensuring the safety and economy during foundation pit dewatering with suspended waterproof curtains. However, there are limited applicable methods to predict the groundwater inflow of circle foundation pit with waterproof curtains in deep unconfined aquifers. In this study, based on Darcy's law and the continuity of water flow, the impact of suspended waterproof curtains on groundwater seepage was initially analyzed during circle foundation pit dewatering in deep unconfined aquifers. Furthermore, an analytical solution was proposed for groundwater inflow of circle foundation pit with suspended waterproof curtains in the unconfined aquifers. The effect of suspended waterproof curtains on seepage area, seepage direction, and seepage path were respectively considered by introducing the buried depth of waterproof curtain, the anisotropy coefficient, and the seepage path reduction coefficient. Finally, based on the self-conducted indoor seepage experiment and other cases (an indoor seepage experiment and two actual engineering projects), this proposed method was applied to conduct a comparative analysis with the existing methods. Results indicated that the proposed method can more reasonably evaluate the groundwater inflow of circle foundation pit with waterproof curtains in the unconfined aquifer, which can provide a better guidance for the groundwater inflow control in the practical dewatering projects. [ABSTRACT FROM AUTHOR]

The seepage field of a suspended waterproof curtain strip foundation pit in a deep phreatic aquifer is theoretically analyzed, and a calculation method for the foundation pit water inflow and water level outside the curtain is derived. In this paper, it is assumed that the horizontal hydraulic gradient of the seepage field above the aquiclude below the bottom of the waterproof curtain decreases linearly. The separation variable method is used to solve the seepage field in the regular area inside the foundation pit, and the hydraulic head distribution function inside the foundation pit is obtained. According to the hydraulic head distribution function inside the foundation pit, the calculation expression of the water inflow of the foundation pit is further deduced theoretically. On this basis, the improved resistance coefficient method is applied to link the water level outside the pit with the solved hydraulic head inside the pit and solved. In addition, the calculation results presented in this study are compared with the calculation results of the existing model and the measured data of the foundation pit project of Yangwan Station, which proves that the analytical method can effectively meet the requirements of engineering applications. [ABSTRACT FROM AUTHOR]

To mitigate unforeseen incidents, such as key block failure or tunnel collapse during excavation, an appropriate support pattern that correlates with the geological conditions of the rock mass at the tunnel face should be designed. Rock mass evaluations should be conducted through geological face mapping during the construction phase, alongside predictions based on field investigations during the design phase. When marked discrepancies are identified, it is customary to convene an on-site evaluation involving a committee of experts. This study develops a digital tunnel face mapping system that utilises mobile devices to facilitate online evaluations during the construction phase. This system effectively replaces the traditional on-site field evaluation method. Tunnel face mapping can be promptly accomplished using images captured at the excavation face, enabling rapid analysis. In conjunction with the mapping capabilities, the developed system was designed to digitally store geological information, which includes parameters such as rock strength distribution, the spacing and length of discontinuities observed during the mapping process, as well as data pertaining to weathering and the groundwater conditions of those discontinuities. This information was then correlated with the rock mass rating sheet to automate the determination of ratings for each parameter, ultimately leading to a conclusive classification of the rock mass quality. By employing this system for tunnel face mapping and rock quality evaluation, we significantly reduced the discrepancies in the evaluation results that often arise due to the subjective judgement of geologists, as well as human errors that can occur throughout the rating process.

Various hydrogeological problems like groundwater inflow, water table drawdown, and water pressure redistribution may be encountered in the construction of hydraulic projects. How to accurately predict the occurrence of groundwater inflow and assess the drainage effect during construction are still challenging problems for engineering designers. Taking the Jinzhai pumped storage power station (JPSPS) of China as an example, this paper aims to use different methods to calculate the water inflow rates of an underground powerhouse and evaluate the drainage effect caused by tunnel inflow during construction. The methods consist of the analytical formulas, the site groundwater rating (SGR) method, and the Signorini type variational inequality formulation. The results show that the analytical methods considering stable water table may overestimate the water inflow rates of caverns in drained conditions, whereas the SGR method with available hydro-geological parameters obtains a qualitative hazard assessment in the preliminary phase. The numerical solutions provide more precise and reliable values of groundwater inflow considering complex geological structures and seepage control measures. Moreover, the drainage effects, including a seepage-free surface, pore water pressure redistribution, and hydraulic gradient, have been accurately evaluated using various numerical synthetic cases. Specifically, the faults intersecting on underground caverns and drainage structures significantly change the groundwater flow regime around caverns. This comparative study can not only exactly identify the capabilities of the methods for cavern inflow in drained conditions, but also can comprehensively evaluate the drainage effect during cavern construction.

A thermal system in the very deep Lake Tazawa (maximum depth, 423 m) was investigated by estimating the heat budget. In the heat budget estimate, the net heat input at the lake's surface and the heat input by river inflow and groundwater inflow were considered. Then, the heat loss by snowfall onto the lake's surface was taken into account. Meanwhile, the lake water temperature was monitored at 0.2 m to the bottom by mooring temperature loggers for more than two years. The heat storage change of the lake from the loggers was calibrated by frequent vertical measurements of water temperature at every 0.1 m pitch by a profiler with high accuracy (±0.01 °C). The heat storage change (W/m2) obtained by the temperature loggers reasonably accorded to that from the heat budget estimate. In the heat budget, the net heat input at lake surface dominated the heat storage change, but significant heat loss by river inflow sporadically occurred, caused by the relatively large discharge from a reservoir in the upper region. How deeply the vertical water circulation in the lake occurs in winter was judged according to the differences between water temperatures at 0.2 m depth and at the bottom and between vertical profiles of dissolved oxygen over winter. It is strongly suggested that the whole water circulation process does not occur every winter, and if it does, it is very weak. A consistent increase in the water temperature at the bottom is probably due to the conservation of geothermal heat by high frequency of incomplete vertical water circulation. [ABSTRACT FROM AUTHOR]

The seepage field of a suspended waterproof curtain strip foundation pit in a deep phreatic aquifer is theoretically analyzed, and a calculation method for the foundation pit water inflow and water level outside the curtain is derived. In this paper, it is assumed that the horizontal hydraulic gradient of the seepage field above the aquiclude below the bottom of the waterproof curtain decreases linearly. The separation variable method is used to solve the seepage field in the regular area inside the foundation pit, and the hydraulic head distribution function inside the foundation pit is obtained. According to the hydraulic head distribution function inside the foundation pit, the calculation expression of the water inflow of the foundation pit is further deduced theoretically. On this basis, the improved resistance coefficient method is applied to link the water level outside the pit with the solved hydraulic head inside the pit and solved. In addition, the calculation results presented in this study are compared with the calculation results of the existing model and the measured data of the foundation pit project of Yangwan Station, which proves that the analytical method can effectively meet the requirements of engineering applications.

A thermal system in the very deep Lake Tazawa (maximum depth, 423 m) was investigated by estimating the heat budget. In the heat budget estimate, the net heat input at the lake’s surface and the heat input by river inflow and groundwater inflow were considered. Then, the heat loss by snowfall onto the lake’s surface was taken into account. Meanwhile, the lake water temperature was monitored at 0.2 m to the bottom by mooring temperature loggers for more than two years. The heat storage change of the lake from the loggers was calibrated by frequent vertical measurements of water temperature at every 0.1 m pitch by a profiler with high accuracy (±0.01 °C). The heat storage change (W/m2) obtained by the temperature loggers reasonably accorded to that from the heat budget estimate. In the heat budget, the net heat input at lake surface dominated the heat storage change, but significant heat loss by river inflow sporadically occurred, caused by the relatively large discharge from a reservoir in the upper region. How deeply the vertical water circulation in the lake occurs in winter was judged according to the differences between water temperatures at 0.2 m depth and at the bottom and between vertical profiles of dissolved oxygen over winter. It is strongly suggested that the whole water circulation process does not occur every winter, and if it does, it is very weak. A consistent increase in the water temperature at the bottom is probably due to the conservation of geothermal heat by high frequency of incomplete vertical water circulation.

The article reviews the issues concerned with correctness of the engineering-geological and hydrogeological assessment of the Upper Kotlin clays, which serve as the foundation or host medium for facilities of various applications. It is claimed that the Upper Kotlin clays should be regarded as a fissured-block medium and, consequently, their assessment as an absolutely impermeablestratum should be totally excluded. Presence of a high-pressure Vendian aquifer in the lower part of the geological profile of the Vendian sediments causes inflow of these saline waters through the fissured clay strata, which promotes upheaval of tunnels as well as corrosion of their lining. The nature of the corrosion processes is defined not only by the chemical composition and physical and chemical features of these waters, but also by the biochemical factor, i.e. the availability of a rich microbial community. For the first time ever, the effect of saline water inflow into the Vendian complex on negative transformation of the clay blocks was studied. Experimental results revealed a decrease in the clay shear resistance caused by transformation of the structural bonds and microbial activity with the clay’s physical state being unchanged. Typification of the Upper Kotlin clay section has been performed for the region of Saint Petersburg in terms of the complexity of surface and underground building conditions. Fissuring of the bedclays, the possibility of confined groundwater inflow through the fissured strata and the consequent reduction of the block strength as well as the active corrosion of underground load-bearing structures must be taken into account in designing unique and typical surface and underground facilities and have to be incorporated into the normative documents.

Lake Tazawa, the deepest lake (423.4 m depth at maximum) in Japan underwent drastically changed water quality in 1940, because volcanic water from two active volcanos was then drawn into the lake for power generation and irrigation. Thereby, the pH of lake water decreased from 6.7 to 4.2, which exterminated a land-locked type of sockeye salmon, Oncorhynchus nerkakawamurae (locally called Kunimasu trout). Additionally, the mean residence time of lake water changed from 195 years to 8.9 years by rapidly increasing the outflow for power generation and irrigation. In this study, long-term chemical fluxes controlling lake water chemistry were obtained, and a groundwater water cycle system between the lake and the volcano was explored by estimating hydrological and chemical budgets of the lake. In the chemical budget estimate, two ionic species, SO42− and Cl−, in volcanic fluids were chosen and each mass conservation equation was yielded. The hydrological budget estimate gave us the net groundwater inflow at −1.36 m3/s on average over three periods in 2020–2021, and then the simultaneous equation coupled with the chemical budget equation allowed us to separate into groundwater inflow and outflow at 6.01 m3/s and 7.37 m3/s, averaged over the three periods, respectively. The evaluated groundwater inflow and outflow were compared with those of the other crater or caldera lakes. The linear relationship between the lake volume and the magnitude of groundwater inflow or outflow suggests that the groundwater cycle scale in such a lake increases with the magnitude of the volcanic eruption to have formed the lake. [ABSTRACT FROM AUTHOR]

Due to the existence of a large number of discontinuous fractures and interfaces in tunnel surrounding rocks, the groundwater inflow into tunnel generally presents significant anisotropy. Therefore, it is of great significance to consider the anisotropic permeability when dealing with water gushing-induced engineering accidents in water-rich mountain tunnels with large burial depth. In this study, based on the complex variable method and the seepage flow theory, a theoretical model of water inflow into a deep-buried circular tunnel in a fully saturated, anisotropic and semi-infinite aquifer is developed. The influence of grouted zone, initial support and secondary lining is fully considered. By comparison to the existing analytical methods and numerical results, the reliability of this proposed analytical solution is well validated. It is indicated from the parametric study that the groundwater inflow into tunnel presents an upward trend with an increasing value of the strata permeability in the vertical direction. Moreover, the water inflow rate and the total water head decrease with the growth of the thickness of grouting circle. It is suggested that reasonable grouting thickness and permeability should be controlled to enhance the grouting effect. This study provides a practical method for estimating the water inflow into a deep-buried, grouted and lined mountain tunnel considering the anisotropic strata permeability. [ABSTRACT FROM AUTHOR]

The Çeltikçi Coal Basin is a newly discovered coal basin in Central Anatolia where 11 years of open-cut mining has been planned. The bulk of the mining will be conducted below the regional water table; hence, determination of the dewatering requirements and proper design of the dewatering wells plays a critical role. This study (i) defined the dewatering requirements of the open-pit mine, (ii) established a dewatering well design for the area, and (iii) assessed the anticipated impacts of the dewatering activities. For this purpose, a 3-D numerical groundwater flow model was developed using the FEFLOW software. Yearly dewatering requirements were determined under transient conditions. For the dewatering well simulations, two types of dewatering wells were considered: permanent wells located at the open pit boundary that would increase in number as the excavation proceeds and wells located at the periphery of the yearly excavated area that would be operational for about two years. The simulation results indicated that 894 wells were required to satisfy dry working conditions; the average pumping rate throughout the mine life was calculated as 322 L/s. The impacts of open-pit dewatering on groundwater resources were assessed in terms of spring discharge and base flow rates in the nearby Kirmir stream. As a result of dewatering, most of the village water supply springs and fountains will dry up in the area. In addition, the base flow rates to the Kirmir stream will be decreased by 15%. [ABSTRACT FROM AUTHOR]

Due to the existence of tiny cracks in rock, underground engineering has begun to consider how to divert a large amount of groundwater. To divert groundwater more effectively, it is necessary to master the seepage characteristics of fluids in the micropores of rocks. Based on rock samples obtained from an underground engineering site, this paper analyzes the microscopic pore structure of the rock through a combination of laboratory tests and numerical simulations and inputs this information into a computer model. The fluid seepage state in the rock under different conditions is simulated in the computer model, and parameters such as the fluid seepage velocity in the rock are obtained. Afterwards, it has been verified by engineering practice that the smallest remaining water inflow can reach 0.06‰. The results of this paper can effectively guide the discharge of groundwater to better manage water resources, greatly reduce the pollution of groundwater in construction and production environments, and reduce the pollution caused by grouting projects. Furthermore, the cleanliness and safety of underground engineering construction and production could be ensured. [ABSTRACT FROM AUTHOR]

The main objective of this study is to estimate the amount of groundwater inflow into Dorud-Khorramabad railway tunnel. To this end, in the first place, existing approaches of predicting groundwater inflow into tunnel was reviewed. According to the literature, up to now, a wide range of approaches have been proposed in order to predict the groundwater inflow into tunnel which can be classified into three distinct groups including, analytical solutions, empirical equations, and numerical modeling. Analytical solutions and empirical equations are mainly developed based on the given hypotheses and specific data sets, respectively, and should be applied in similar conditions. On the other hand, results obtained from numerical modeling are generally dependent on a wide range of parameters. Literature review revealed that one of the most effective parameters on the numerical modeling results is model extent, which controls not only final results but also numerical runtime. Hence, a sensitivity analysis is performed in order to investigate the effect of model extent on numerical results. The results demonstrated that increasing model extent decreases the groundwater inflow rate, and for a large model extent (greater than 1000), the amount of groundwater inflow tends to a constant value. In the second part, analytical solutions and finite element numerical modeling are applied for estimating the amount of groundwater inflow into Dorud–Khorramabad railway tunnel. The results indicate that the groundwater inflow into the tunnel, based on analytical methods, gives higher values than the numerical modeling. Assumptions and simplifications may justify this difference in analytical methods, accordingly, it can be inferred that if an appropriate model extent selected, the results of the numerical model based on the fact in the project can be more reliable.

Brook trout Salvelinus fontinalis populations inhabiting groundwater‐fed, headwater streams are sensitive to biotic and abiotic changes caused by anthropogenic actions in their native range but can be very resilient in their introduced range. Brook trout have maintained a self‐sustaining population in the Little Plover River, Wisconsin, despite fish kills during extreme low flows between 2005 and 2009 caused by groundwater pumping and limited precipitation. Increased understanding of brook trout sensitivity and resilience in headwater streams can aid restoration, conservation and eradication efforts. Therefore, we evaluated their movements, survival and spawning behaviours in the Little Plover River using a PIT antenna array (July 2016–July 2019) and spawning redd surveys (2017–2018) paired with estimated groundwater inputs. Tagged individuals often exhibited localised, nocturnal movements for most of the year. However, movements increased and shifted to a diurnal pattern with decreased photoperiod and water temperature beginning during spawning and continuing throughout winter (November–February). Spawning movements primarily (90%) occurred in the upstream direction, with consistent patterns of short (rkm <0.9, 64.8.9–70.7%), moderate (rkm =0.9 – 3.5, 20.0–30.2%) and long (rkm ≥4.5, 4.5–6.2%) distance movements across the three spawning periods. Monthly survival estimates ranged from 72.1 to 98.9% throughout the study (mean =91.5%) and were consistently lowest during winter and spring. Redd surveys indicated spawning peaked in mid‐November and redds were more concentrated in upstream reaches and in areas with higher estimated groundwater inflows in 2017 but not in 2018 when surface flows were higher. Our results increase understanding of brook trout daily and seasonal movements, monthly and seasonal survival, and spawning behaviours including relative to groundwater and surface flows in headwater streams, further informing management, conservation, and eradication efforts. [ABSTRACT FROM AUTHOR]

Properly accounting for the effect of heterogeneity of aquifers and accurately predicting mine water inflow during the mining process is still a challenging problem in China. We developed a stochastic modelling methodology that considers a large range of possible multi-scale fracture configurations and heterogeneous porous rock to predict mine water inflow close to the observed data. The coupled discrete fracture–rock matrix models were built for the Binhu coal mine 16,112 working face with the Monte Carlo method. The models were solved using the embedded discrete fracture model to calculate groundwater inflow from the aquifer beneath the coal seam floor. The calculated results and the observed groundwater inflows in the field agreed well. Sensitivity analysis indicates that groundwater inflow increases with increased fracture length and fracture density. The effect of natural fractures introduces a large uncertainty for the models, due to the existence of long fractures that could act as conduits between the Ordovician limestone and no. 14 aquifers. The results highlight the importance of multi-scale fractures on modeling and simulating flow in the mine area. [ABSTRACT FROM AUTHOR]

The project of interest involving a hydroelectrical diversion tunnel through a crystalline rock massif in the Alps required a detailed hydrogeological study to forecast the magnitude of water inflows within the tunnel and possible effects on groundwater flow. The tunnel exhibits a length of 9.5 km and is located on the right side of the Toce River in Crevoladossola (Verbania Province, Piedmont region, northern Italy). Under the geological framework of the Alps, the tunnel is located within the Lower Penninic Nappes in the footwall of the Simplon Normal Fault, and the geological succession is mostly represented by Antigorio gneiss (meta-granites) and Baceno metasediments (metacarbonates). Due to the presence of important mineralized springs for commercial mineral water purposes, the abovementioned hydrogeological study focused on both quantity and quality aspects via rainfall data analysis, monitoring of major spring flow rates, monitoring of hydraulic heads and pumping rates of existing wells/boreholes, hydrochemical and isotopic analysis of springs and boreholes and hydraulic tests (Lefranc and Lugeon). The resulting conceptual model indicated dominant low-permeability (aquitard) behavior of the gneissic rock masses, except under conditions of intense fracturing due to tectonization, and aquifer behavior of the metasedimentary rocks, particularly when interested by dissolution. Groundwater flow systems are mainly controlled by gravity. The springs located near the Toce River were characterized by high mineralization and isotopic ratios, indicating long groundwater flow paths. Based on all the data collected and analyzed, two parametric methods were applied: 1) the Dematteis method, slightly adapted to the case study and the available data, which allows assessment of both potential inflows within the tunnel and potential impacts on springs (codified as the drawdown hazard index; DHI); 2) the Cesano method, which only allows assessment of potential inflows within the tunnel, thereby discriminating between major and minor inflows. Contemporarily, a groundwater flow model was implemented with the equivalent porous medium (EPM) approach in MODFLOW-2000. This model was calibrated under steady-state conditions against the available data (groundwater levels inside wells/piezometers and elevation and flow rate of springs). The Dematteis method was demonstrated to be more reliable and suitable for the site than was the Cesano method. This method was validated considering a tunnel through gneissic rock masses, and this approach considered intrinsic parameters of rock masses more notably than morphological and geomorphological factors were considered. The Cesano method relatively overestimated tunnel inflows, considering variations in the topography and overburden above the tunnel. Sensitivity analysis revealed a low sensitivity of these parametric methods to parameter values, except for the rock quality designation (RQD) employed to represent the fracturing degree. The numerical model was calibrated under ante-operam conditions, and sensitivity analysis evaluated the influence of uncertainties in the hydraulic conductivity (K) values of the different hydrogeological units. The hydraulic head distribution after tunnel excavation was forecasted considering three scenarios, namely, a draining tunnel, tunnel as a water loss source, and tunnel sealed along its aquifer sectors, considering 3 levels of K reduction. Tunnel impermeabilization was very effective, thus lowering the drainage rate and impact on springs. The model quantitatively defined tunnel inflows and the effects on spring flow at the surface in terms of flow rate decrease. The Dematteis method and numerical model were combined to obtain a final risk of impact on the springs. This study likely overestimated the risk because all the values assigned to the parameters were chosen in a conservative way, and the steady-state numerical simulations were also very conservative (the transient state in this hydrogeological setting supposedly lasts 1–3 years). Monitoring of the tunnel and springs during tunnel boring could facilitate the feedback process.

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Study region: Two giant pockmarks in Lake Banyoles (NE Spain) have been surveyed over the last 35 years. The giant pockmark ‘B1’ has maintained an ‘eruptive’ mode with permanent groundwater discharge, whereas, the giant pockmark ‘B2’ has displayed alternating quiescent and eruptive phases. Study focus: Interannual variability of lake-subsurface groundwater discharge in both pockmarks and the main lake aquifer level correlates with changes in the accumulated rainfall during the previous 10 months in the north-east of Spain. In the eruptive phase, the lutocline, marking the top of suspended sediments, is warmer than the ambient lake water and generates a turbid hydrothermal plume.New hydrological insights for the Region: Results show that the permanent hydrothermal plume at pockmark B1 is no longer penetrating the lake's background stratification due to the loss of plume buoyancy. The available data demonstrate that current climate change coupled with a depletion of groundwater resources has strongly impacted the hydrogeology and limnology of the main pockmark of the lake and also the distribution of suspended sediment in the water column.

When estimating groundwater inflow into lined tunnels in water-rich regions, waterproofing and drainage systems (WDS) are usually ignored or not fully considered in existing analytical solutions. In this study, a water drainage seepage model considering drainage pipes, waterproof membranes, and geotextiles was developed. An analytical solution was then derived to predict groundwater inflow into composite-lined tunnels. The proposed analytical solution can be reduced to Goodman's solution for an unlined tunnel. When only the initial lining was considered, the difference between the proposed analytical solution and Wang's solution (Tunn Undergr Sp Tech 23(5):552–560, 2008) was less than 0.5%. Subsequently, the proposed analytical solution was further verified using a numerical model and good agreement between both models was observed. Finally, the relationships between groundwater inflow and the parameters of composite linings were investigated. The results of this study suggest the following: (1) groundwater inflow significantly decreases with an increase in the distance between two circular drainage pipes; (2) the higher the rock permeability, the more significant the WDS effect on groundwater inflow; and (3) when the rock permeability exceeds 1 × 10−6 m/s, WDS effects should be considered in the design of WDS. The results of this study are helpful for the optimal design of WDS for tunnels, such as the estimation of the initial lining permeability and thickness, distance between circular drainage pipes, and geotextile hydraulic conductivity. Additionally, the application of the proposed solution could provide a basis for analyzing potential adverse environmental impacts caused by tunnel drainage. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to the existence of tiny cracks in rock, underground engineering has begun to consider how to divert a large amount of groundwater. To divert groundwater more effectively, it is necessary to master the seepage characteristics of fluids in the micropores of rocks. Based on rock samples obtained from an underground engineering site, this paper analyzes the microscopic pore structure of the rock through a combination of laboratory tests and numerical simulations and inputs this information into a computer model. The fluid seepage state in the rock under different conditions is simulated in the computer model, and parameters such as the fluid seepage velocity in the rock are obtained. Afterwards, it has been verified by engineering practice that the smallest remaining water inflow can reach 0.06‰. The results of this paper can effectively guide the discharge of groundwater to better manage water resources, greatly reduce the pollution of groundwater in construction and production environments, and reduce the pollution caused by grouting projects. Furthermore, the cleanliness and safety of underground engineering construction and production could be ensured.

Healthy river ecosystems require the interaction of many physical and biological processes to maintain their status. One physical process supporting biogeochemical cycling is hydrologic exchange (i.e., hydrologic exchange flows, HEFs) between relatively fast-flowing channel waters and slower-flowing surface and subsurface waters (lateral and vertical). Land uses adjacent to rivers have the potential to alter the water quality of off-channel surface and subsurface waters, and HEFs therefore have the potential to deliver solutes associated with river-adjacent land uses to rivers. HEFs can be nonpoint, diffuse sources of pollution, making the ultimate pollution source difficult to identify, especially in large rivers. Here, we seek to identify HEFs in the Columbia River near Richland, WA by looking for anomalies in temperature and electrical conductivity (EC) along the bed of the river in February, June, July, August, and November 2018. These are ultimately the “ends” of HEFs as they are locations of subsurface inflow to the river. We found these anomalies to be a combination of warmer or colder and higher (but not lower) EC than river water. We identified a majority of warm anomalies in February and July 2018, and majority cold anomalies in June, August, and November 2018. High-EC anomalies were found mostly in February, August, and November. Combined, we observe a shift from warm, high EC anomalies dominating in February to equivalent EC, warm anomalies in June, to equivalent EC, cool anomalies dominating July. In August, we also measured dissolved nitrate (NO3-) in-situ to determine whether anomalies were associated with increased NO3- loading to the river, especially along the eastern shoreline, which is dominated by agricultural land use. Inflows along the eastern shoreline have greater concentrations of nitrate than river water (up to 10 mg N–NO3-/L). This research demonstrates that HEFs are temporally and spatially dynamic transferring heat and solutes to rivers.

Understanding groundwater–surface water (GW–SW) interactions is vital for water management in karstic catchments due to its impact on water quality. The objective of this study was to evaluate and compare the applicability of seven environmental tracers to quantify and localize groundwater exfiltration into a small, human‐impacted karstic river system. Tracers were selected based on their emission source to the surface water either as (a) dissolved, predominantly geogenic compounds (radon‐222, sulphate and electrical conductivity) or (b) anthropogenic compounds (predominantly) originating from wastewater treatment plant (WWTP) effluents (carbamazepine, tramadol, sodium, chloride). Two contrasting sampling approaches were compared (a) assuming steady‐state flow conditions and (b) considering the travel time of the water parcels (Lagrangian sampling) through the catchment to account for diurnal changes in inflow from the WWTP. Spatial variability of the concentrations of all tracers indicated sections of preferential groundwater inflow. Lagrangian sampling techniques seem highly relevant for capturing dynamic concentration patterns of WWTP‐derived compounds. Quantification of GW inflow with the finite element model FINIFLUX, based on observed in‐stream Rn activities led to plausible fluxes along the investigated river reaches (0.265 m3 s−1), while observations of other natural or anthropogenic environmental tracers produced less plausible water fluxes. Important point sources of groundwater exfiltration can be ascribed to locations where the river crosses geological fault lines. This indicates that commonly applied concepts describing groundwater–surface water interactions assuming diffuse flow in porous media are difficult to transfer to karstic river systems whereas concepts from fractured aquifers may be more applicable. In general, this study helps selecting the best suited hydrological tracer for GW exfiltration and leads to a better understanding of processes controlling groundwater inflow into karstic river systems. [ABSTRACT FROM AUTHOR]

Understanding the hydrologic connectivity between kettle holes and shallow groundwater, particularly in reaction to the highly variable local meteorological conditions, is of paramount importance for tracing water in a hydro(geo)logically complex landscape and thus for integrated water resource management. This article is aimed at identifying the dominant hydrological processes affecting the kettle holes' water balance and their interactions with the shallow groundwater domain in the Uckermark region, located in the north‐east of Germany. For this reason, based on the stable isotopes of oxygen (δ18O) and hydrogen (δ2H), an isotopic mass balance model was employed to compute the evaporative loss of water from the kettle holes from February to August 2017. Results demonstrated that shallow groundwater inflow may play the pivotal role in the processes taking part in the hydrology of the kettle holes in the Uckermark region. Based on the calculated evaporation/inflow (E/I) ratios, most of the kettle holes (86.7%) were ascertained to have a partially open, flow‐through‐dominated system. Moreover, we identified an inverse correlation between E/I ratios and the altitudes of the kettle holes. The same holds for electrical conductivity (EC) and the altitudes of the kettle holes. In accordance with the findings obtained from this study, a conceptual model explaining the interaction between the shallow groundwater and the kettle holes of Uckermark was developed. The model exhibited that across the highest altitudes, the recharge kettle holes are dominant, where a lower ratio of E/I and a lower EC was detected. By contrast, the lowest topographical depressions represent the discharge kettle holes, where a higher ratio of E/I and EC could be identified. The kettle holes existing in between were categorized as flow‐through kettle holes through which the recharge takes place from one side and discharge from the other side. [ABSTRACT FROM AUTHOR]

Summary: This paper presents an analytical evaluation on the influence of foam conditioning on groundwater inflow at shield tunnel cutting face by the force‐equilibrium principle. Three key variables are highlighted, namely, the maximum foam infiltration distance, the critical infiltration distance, and the hydraulic conductivity of foam‐conditioned soil or rock fissure. To capture the variation of water level induced by foam injection, a dynamic water‐level equation is considered in the force‐equilibrium principle. The proposed analytical equations are employed to analyze a water inflow case during shield tunneling in a weathered mylonite fault. The results indicate that the hydraulic conductivity of foam‐conditioned mylonite and the infiltration distance decrease with an increase of shear stress of foam fluid. A three‐dimensional finite element model is employed to validate the analytical solutions. The comparison between the observed and calculated results confirms that the proposed method can predict groundwater inflow in foam‐conditioned soils. [ABSTRACT FROM AUTHOR]

To investigate the hydrology of Utah Lake, we analyzed the hydrogen (δ2H) and oxygen (δ18O) stable isotope composition of water samples collected from the various components of its system. The average δ2H and δ18O values of the inlets are similar to the average values of groundwater, which in turn has a composition that is similar to winter precipitation. This suggests that snowmelt-fed groundwater is the main source of Utah Valley river waters. In addition, samples from the inlets plot close to the local meteoric water line, suggesting that no significant evaporation is occurring in these rivers. In contrast, the lake and its outlet have higher average δ-values than the inlets and plot along evaporation lines, suggesting the occurrence of significant evaporation. Isotope data also indicate that the lake is poorly mixed horizontally, but well mixed vertically. Calculations based on mass balance equations provide estimates for the percentage of input water lost by evaporation (~47%), for the residence time of water in the lake (~0.5 years), and for the volume of groundwater inflow (~700 million m3) during the period April to November. The short water residence time and the high percentage of total inflow coming from groundwater might suggest that the lake is more susceptible to groundwater pollution than to surface water pollution.

The objective of this study is to make a comparison among different methods used for evaluation of steady state groundwater inflow to a shallow circular cross section tunnel. These methods include: analytical solutions, empirical methods and numerical modelling. Analytical formulas provide an estimation of inflow rate based on some simplifying assumptions which are somehow unrealistic. Therefore, their results are over/underestimated. Empirical methods are presented based on the experiences of different tunnel projects and they mostly provide an appropriate qualitative estimation; while, their quantitative predictions are not desirable. Despite analytical and empirical approaches, numerical modelling is a suitable tool for solving complex geomechanical and hydrogeological conditions. Hence, their results are more reliable and precise for designation of efficient drainage systems. In this study, groundwater inflow into Tabriz Metro-Line 2 ( TML2 ) is evaluated by means of these methods and their results were compared. The results indicated that all of the methods provide consistent results, however, it is inferred that in the absence of sufficient data, Raymer equation can provide more reliable estimation of inflow rate for shallow tunnels in comparison to other analytical and empirical solutions due to its higher correlation with numerical results. [ABSTRACT FROM AUTHOR]

The flow of water into a tunnel, through the surrounding rock mass and the tunnel lining, has important implications for tunnel design and tunnel condition assessment. The hydraulic conductivity of the lining is a major controlling factor on the water inflow rate. Previous work had been mainly based on the assumption of constant hydraulic conductivity of the lining. In this work, the existing analytical models of water flow through a tunnel lining under steady-state, saturated conditions are extended to incorporate a linear variation of hydraulic conductivity with distance from the tunnel wall. The inhomogeneity of a lining is shown to have a significant impact on water inflow rate and water pressure distribution according to the model. The relation between lining inhomogeneity and other hydraulic parameters was established. This model can be used to predict the hydraulic pressure and crack condition at the outer face of the lining based on measured water inflow rate and the crack condition at the inner face, with significantly increased accuracy compared with the existing models based on constant hydraulic conductivity. Design charts are also developed for engineering applications. [ABSTRACT FROM AUTHOR]

The main purpose of this research is to introduce a new method for estimating the groundwater inflow rate into tunnels excavated in rock environments. The Groundwater Seepage Rate (GSR) is a novel analytical method that has the capability to assess the rock mass potential in conducting the groundwater into tunnels. Geological and hydraulic parameters and radius of the tunnel are the main parameters used in the GSR method. In this method, geological parameters are defined based on the characteristics of the joint sets including the strike, number, spacing and aperture of joints of each joint set. In addition, hydraulic head and hydraulic conductivity are other principle inputs of the proposed model. In GPR method, the rate of groundwater inflow has been evaluated in 3D dimensions and efforts were made to obtain acceptable values by creating rational correlations among input data. The taking account of joints condition in tunnel and the direct effect of tunnel radius, the separate study of the joint sets and the role of fracture systems in the groundwater conductivity into excavated openings are the main advantages of this model. According to the results of this study, GSR method can provide better estimations of the inflow volume for rock masses with elastic behavior in which fracture systems have been developed. Finally, in the end this paper for validation of GSR values, the results of this method were compared with the obtained results of empirical methods and observed groundwater inflow in various geological units of the Zagros tunnel in Iran. Additionally, the calculated value of groundwater inflow based on GSR method shows good compatibility with empirical methods. [ABSTRACT FROM AUTHOR]

The spatial and temporal scales of hyporheic exchange within the stream corridor are controlled by stream discharge and groundwater inflow interacting with streambed morphology. While decades of study have resulted in a clear understanding of how morphologic form controls hyporheic exchange at the feature scale, we lack comparable predictive power related to stream discharge and the spatial structure of groundwater inflows at the reach scale, where spatial heterogeneity in both geomorphic setting and hydrologic forcing are present. In this study, we simulated vertical hyporheic exchange along a 600 m mountain stream reach under high, medium, and low stream discharge while considering groundwater inflow as negligible, spatially uniform, or proportional to upslope accumulated area. Most changes to hyporheic flow path residence time or length in response to stream discharge were small (<5%), suggesting that discharge is a secondary control relative to morphologically driven hyporheic exchange. Groundwater inflow was a primary control and mostly caused decreases in hyporheic flow path residence time and length. This finding generally agrees with expectations from the literature; however, flow path response was not consistent across the study reach. Instead, we found that flow paths driven by large hydraulic gradients coinciding with large morphologic features were less sensitive to changes in groundwater inflow than those driven by hydraulic gradients similar to the valley gradient. Our results indicate that consideration of heterogeneous arrangement of morphologic features is necessary to differentiate between hyporheic flow paths that persist in time and those that are sensitive to changing hydrologic conditions. [ABSTRACT FROM AUTHOR]

Estimation of groundwater inflow into underground opening is of critical importance for the design and construction of underground structures. Groundwater inflow into a pilot underground storage facility in China was estimated using analytical equations, numerical modeling and field measurement. The applicability of analytical and numerical methods was examined by comparing the estimated and measured results. Field geological investigation indicated that in local scale the high groundwater inflows are associated with the appearance of open joints, fractured zone or dykes induced by shear and/or tensile tectonic stresses. It was found that 8 groundwater inflow spots with high inflow rates account for about 82% of the total rate for the 9 caverns. On the prediction of the magnitude of groundwater inflow rate, it was found that could both (Finite Element Method) FEM and (Discrete Element Method) DEM perform better than analytical equations, due to the fact that in analytical equations simplified assumptions were adopted. However, on the prediction of the spatial distribution estimation of groundwater inflow, both analytical and numerical methods failed to predict at the present state. Nevertheless, numerical simulations would prevail over analytical methods to predict the distribution if more details in the simulations were taken into consideration. [ABSTRACT FROM AUTHOR]

As an indispensable component of groundwater circulation, groundwater evapotranspiration rate ( ET G ) estimation using water table fluctuations is a hot research topic in the past decades. However, most existing methods for estimating ET G using either diurnal or seasonal water table fluctuations are based on the assumptions that groundwater recharge equals 0 in the whole period and ET G equals 0 in a specific duration of time. The aim of the current study is to develop a method to estimate ET G when both assumptions do not apply. In the discharge area of a semi-arid catchment in the Ordos Plateau, NW China, it is found out that the water table fluctuations are influenced greatly by recharge, ET G and the vertical inflow rate ( q in ) in the seasonal scale but are controlled by atmospheric pressure instead of evapotranspiration in the diurnal scale, which implies that the existing methods are not applicable. Therefore, we propose a method to estimate ET G and q in using the seasonal water table fluctuations based on the assumptions that q in is stable throughout the year and ET G has a linear relationship to the reference evapotranspiration ( ET 0 ). It is found out that q in is around 1.12 mm/d, and the ratio of ET G to ET 0 is around 0.4. ET G in April through July with the highest ET 0 of the year is found to be around 3 mm/d, which is much larger than q in , thus leads to significant decline in water table. ET G in November with the lowest ET 0 of the unfrozen period is found to be 1.0 mm/d, which is slightly smaller than q in , thus results in a weak increase in water table. The vertical component of regional groundwater inflow is found to exceed precipitation recharge, indicating that regional groundwater inflow plays the major role on maintaining the shallow water table in the discharge area. Groundwater evapotranspiration is also found to exceed precipitation recharge in most time of the unfrozen period, indicating a specified-flux upper boundary with water loss in the discharge area of an arid catchment. The proposed method could be applied to similar study areas and is critical to understand the budget of groundwater. [ABSTRACT FROM AUTHOR]