Hydrogeological Properties Research Articles

Biased Estimation of Groundwater Velocity from a Push-Pull Tracer Test Due to Plume Density and Pumping Rate

The single-well push-pull tracer test is a convenient and cost-effective tool to estimate hydrogeological properties of a subsurface aquifer system. However, it has a limitation that test results can be affected by various experimental designs. In this study, a series of laboratory-scale push-pull tracer tests were conducted under various conditions controlling input tracer density, pumping rate, drift time, and hydraulic gradient. Based on the laboratory test results, numerical simulations were performed to evaluate the effects of density-induced plume sinking and pumping rate on the proper estimation of groundwater background linear velocity. Laboratory tests and numerical simulations indicated that the actual linear velocity was underestimated for the higher concentration of the input tracer because solute travel distance and direction during drift time were dominantly affected by the plume density. During the pulling phase, reasonable pumping rates were needed to extract the majority of injected tracer mass to obtain a genuine center of mass time (tcom). This study presents a graph showing reasonable pumping rates for different combinations of plume density and background groundwater velocity. The results indicate that careful consideration must be given to the design and interpretation of push-pull tracer tests.

Coseismic Groundwater Drawdown Along Crustal Ruptures During the 2016 Mw 7.0 Kumamoto Earthquake

AbstractGroundwater‐level changes after earthquakes provide insight into changes in hydrogeological properties such as permeability and pore pressure. Quantifying such changes, both their location and magnitude, is usually hindered by limited data. Using extensive high‐resolution water‐level monitoring records, we provide direct evidence of significant groundwater drawdown (4.74‐m maximum) over a 160‐km2 area along crustal ruptures after the Mw 7.0, 2016, Kumamoto earthquake. Approximately 106 m3 of water disappeared within 35 min after the main shock. The loss of water was not caused by static‐strain driven pore‐pressure decrease nor by releasing of water through structural pathways, but most likely by water transfer downwards through open cracks. Such changes may impact the security of water resources, the safety of underground waste repositories, and contaminant transport in seismically active areas.

Links between karst hydrogeological properties and statistical characteristics of spring discharge time series: a theoretical study

Physics-based modeling of karst systems remains almost impossible without enough accurate information about the inner physical characteristics. Usually, the only available hydrodynamic information is the spring discharge at the karst outlet. Numerous works in the past decades have used and proven the usefulness of time-series analysis applied to spring discharge, precipitations or even physico-chemical parameters, for interpreting karst hydrological functioning. The main objective of this work is to provide additional insights of to what extent the informative content of the hydrodynamic signal at karst springs is sensitive to karst aquifers internal physical properties. To address this issue, we undertake an empirical approach based on the use of both distributed and physics-based models and on synthetic systems responses. The link between karst hydraulic and physical properties was studied. For this purpose, forward modeling of flow through several simple, constrained and synthetic cases in response to precipitations is undertaken. It allows us to quantify how the statistical characteristics of flow at the outlet are sensitive to changes (1) one hydraulic parameter of the model and (2) in conduit network geometry. The matrix/conduit exchange parameter appeared clearly as a determinant model parameter in the spring discharge simulation. The auto-and cross-correlation functions seem to be of particular interest for the understanding of the karst inner physics. Indeed, these functions are always different, despite not so pronounced configuration differences. This would highlight that there is an informative content within the spring discharge time series and the usefulness of such analysis methods.

The development of conceptual models for the functioning of geothermal systems using hydrogeological, hydrogeochemical and isotopic data: case studies from Rize (NE Turkey)

The hydrogeological and hydrogeochemical properties and isotopic composition of hot and cold water springs in the Ilicakoy and Ayder geothermal areas were investigated and a conceptual model was developed to explain their function. Characteristics of hot groundwater from the Ilicakoy area were: temperature, 63 °C; EC, 6913 µS/cm; pH, 7.2, DO content, 0.75 mg/L; and water type, Na–Ca–HCO3. Characteristics of hot groundwater from the Ayder area were: temperature, 55 °C; EC, 255 µS/cm; pH, 9.2, DO content, 1.9 mg/L; and water type, Na–Ca–CO3–SO4. Ilicakoy has acidic pH values, while those of the Ayder area are alkaline. Carbon in hot water in both areas was derived from inorganic carbon in groundwater and from CO2 in pore spaces in the unsaturated zone. SO2 in hot water was derived from Cenozoic-aged gypsum. Low tritium and high Cl contents in hot waters indicate deep circulation, and Sr was passed from granitic rocks to waters by simple dissolution. High total alpha and total beta values were obtained in the hot waters from the Ilicakoy geothermal area. Ilicakoy and Ayder geothermal spring formation occurred by infiltration of precipitation through fractures in granitic bedrock from the Kackar granitoid, which forms a regionally significant geothermal reservoir. Water of meteoric origin is heated under by a locally steep geothermal gradient, and it rises through bedrock fractures and re-emerges at the ground surface. In the Ilicakoy and Ayder geothermal fields, which are low temperature geothermal systems, the reservoir rock temperature was 80 °C and 149 °C, respectively.

Hydraulic conductivity of quaternary surficial units within the Eklutna Valley, southcentral Alaska

Eklutna Lake is the primary water supply for Anchorage, Alaska; therefore the hydrogeologic properties of Eklutna surficial deposits are important to characterize. However, there is limited data on the hydraulic conductivity of surficial deposits in the Eklutna basin. This study presents hydraulic conductivity (Kfs and Ksat) measurements using two methods: the bottomless bucket and particle size distribution methods. Statistically, the two methods produced similar results; however, the large range in values obtained for Kfs and Ksat suggests there is a great degree of natural variation. One method used a bottomless bucket in place of a ring infiltrometer to measure field-saturated hydraulic conductivity (Kfs). The other method used a sieve-derived particle size distribution to solve a modified Hazen equation for Ksat. Of 47 samples collected in nine surficial geologic units, from poorly-sorted to well-sorted soils, the means of the two datasets were statistically similar: 49 m/day (Kfs) vs. 41 m/day (Ksat). Although the variability between the datasets was significantly different, with a standard deviation ranging from 44 m/day (Kfs) to 75 m/day (Ksat), the Wilcoxon paired-samples and paired t-test results suggest the datasets are statistically similar. Additionally, 98% of the 47 paired values were within one order of magnitude of each other. The methods presented herein can be used for surficial geologic unit delineation, planning purposes and optimizing hydrological models.

Effect of interaction between fluid and fault zone on triggering earthquakes in the shallow crust

Reservoir induced seismicity provides a suitable method for studying the roles of fluid in inducing earthquakes. The fault structure plays a predominant role in the occurrences of earthquakes, and the influences of fluid also cannot be disregarded. In this study, we investigate the active Fairy Mount fault in the Three Gorges Reservoir. Since water impoundment in 2003, more than 4000 detectable earthquakes have occurred along the fault. The vast majority of these earthquakes are associated with the fault and water impoundment. To explore the effects of water-fault interactions on induced earthquakes, a permeability structure of the fault zone is established by a series of geological experiments. Fault rocks, including unconsolidated breccias and fault gouges, collected from a presentative outcrop are employed for detailed microstructural and mineralogical analyses. The results reveal a complex internal fault structure and widespread fluid-rock interactions. The hydrogeological property of the fault exhibits a typical conduit/barrier permeability structure. Highly permeable damage zones act as fluid conduits for the infiltration of reservoir water to the subsurface, while the low permeable fault core renders the fault core as a potential fluids storage area to weaken the fault in the shallow crust. In sum, both the pore pressure changes due to water infiltration and the long-term chemical effect of water on the fault plane promote instability of the fault and induce earthquakes.

Aftershock Patterns in Recent Central Apennines Sequences

AbstractDuring the last 20 years, three seismic sequences affected the Apenninic belt (central Italy): Colfiorito (1997–1998), L'Aquila (2009), and Amatrice Visso‐Norcia Campotosto (2016–2017). They lasted for a long time, with a series of moderate‐to‐large earthquakes distributed over 40‐ to 60‐km‐long Apenninic‐trending segments. Their closeness in space and time suggested to study their aftershock sequences to highlight similarities and differences. Aftershock space migration and the distribution of aftershock interarrival times were studied. Mathematical Morphology and nonparametric statistics were applied to reduce the effect of spatial noise. Parametric analysis in time domain and spectral analysis were performed. Two different types of aftershock sequences were found. The L'Aquila sequence presented a continuous and periodic temporal variation (period ≃120 days) of aftershock activity center along the sequence axis, while the other two sequences showed a piecewise continuous pattern and a shorter duration. We also found two different types of temporal evolution of the mean radial distance between the aftershock hypocenters and the one of a reference event corresponding to the start of a large and fast increase of daily energy release. One type was well described by a simple exponential model, while a power law model was more appropriate for the other one. Furthermore, in the first case, the aftershock interarrival time was very well fitted by an exponential model, while noticeable deviations were present in the other case. A possible explanation was provided in terms of the local geological and hydrogeological properties, which depend on the region location with respect to the Ancona‐Anzio tectonic lineament.

Conditions for shallow geothermal energy utilization in Dinaric karst terrains in Croatia

Hydrogeological and thermogeological properties of the shallow subsurface in the Dinaric karst area of Croatia were investigated in the context of its utilization for ground- and water-source heat pumps (GSHPs and WSHPs). The research encompassed four 100 m deep boreholes with GSHP installations in both coastal and inland Dinaric karst (different limestones and evaporitic rocks at one location), and a set of six exploratory boreholes, abstraction and reinjection wells for WSHP heating and cooling using seawater on the coast (fractured and karstified limestones). It was determined that rock thermal conductivities are favourable for GSHP utilization, but dependent on the wider rock mass characteristics which are hard to predict (size of karst voids and their saturation status). In addition, wells with high enough yield and stabile seawater or groundwater temperatures for WSHP utilization can be designed in appropriate structural settings (tensional fractures and fracture set intersections). Advantages and disadvantages of the utilized methodology have been pointed out, as well as methods which should prove useful in the future, especially if larger systems are planned. Hydrogeological, geotechnical, and thermal risks expected during the drilling, installation, and operational phases have also been identified. Presented case studies have given the insight into heat pump installation options and conditions in Croatian part of the Dinarides, but can be useful to other researchers and engineers both in the Dinarides and in similar karst regions.

Groundwater Storage in High Alpine Catchments and Its Contribution to Streamflow

AbstractThere is limited knowledge about groundwater storage in alpine catchments, although it might strongly influence how these catchments react to earlier snowmelt due to climate change. The objective of the study was to develop and test a method to quantify seasonal groundwater storage in alpine catchments and evaluate how groundwater storage is related to hydrogeological properties. As representative water table observations are challenging to acquire in such environments, we used a water balance approach targeting the main snowmelt period when most groundwater recharge is expected to occur. Based on a detailed quantification of the snow water equivalent at the onset of snowmelt combined with discharge measurements, it is possible to quantify groundwater storage with a low uncertainty even if other terms of the water balance are less well constrained. The application of the method to an 11‐km2 research catchment revealed a large seasonal increase of groundwater storage by 300 mm or 45% of the premelt snow water equivalent. An independent quantification of groundwater storage depletion during the 7‐month‐long recession period provided a similar value of 330 mm, demonstrating that the stored groundwater is available to sustain streamflow. At the end of the recession, catchment outflow still amounted to 0.9 mm/day with a composite bedrock aquifer providing a disproportionally high share as demonstrated by hydrochemical data. The study demonstrates that high alpine aquifers can seasonally redistribute water and stabilize catchment outflow in an otherwise very dynamic environment and thus might strongly influence the response of such catchments to climate change.

Hydraulic properties of injection formations constrained by surface deformation

Wastewater injection over the past decade has increased seismicity in the central USA, in some cases accompanied by detectable surface uplift. Here, we use this uplift to constrain subsurface properties and pore pressure evolution. We apply an advanced multitemporal interferometric algorithm to 35 synthetic aperture radar images acquired by ALOS satellite over four years before the 2012 earthquake sequence in east Texas, where large volumes of wastewater are disposed at depths of ∼800 m and ∼1800 m. To solve for the hydraulic diffusivity of the injection layers, we jointly inverted the injected volume and uplift data, considering a poroelastic layered half space. We find diffusivity values of 0.3±0.1 m2/s and 0.7±0.15 m2/s for shallow and deep injection layers, respectively, which combined with seismically-derived bulk moduli yields permeability values of 5.5±2.6×10−14 m2 and 1.9±0.25×10−13 m2 for these layers, consistent with permeability range reported for Rodessa formation and well test values. Hydraulic conductivity determines the evolution of pore pressure and thus the origin and location of induced seismicity. This study highlights the value of geodetic observations to constrain key hydrogeological properties of injection layers and to monitor the evolution of the subsurface pressure change.

Geoelectrical investigations for aquifer characterization and geoenvironmental assessment in northern Morocco

The Mediterranean mountains of Morocco (“Rif”) show an intense sensitivity to hydro-climatic hazards. Hydrologic achievements are thwarted by a series of constraints that request strategic consolidation. The acceleration of socioeconomic activities is causing an increasing pressure on water resources that are already facing insufficiency and degradation problems. This paper aims at geophysical characterization of the most important intramountainous alluvial aquifer on the Rif, Ghis–Nekor. Its electrical and hydrogeological properties are investigated through a correlation of 2D electrical resistivity tomography (ERT), vertical electrical sounding (VES) and borehole data. The results have shown that this monolayer coastal aquifer is constituted of large coarse sand, gravel and pebble deposits that overlay substrata of different hydrogeological and electrical types. A geoenvironmental survey was also carried out in the coastal zone and near the uncontrolled waste landfill of Beni Bouayach. The 2D ERT profiles indicate an increase of marine water intrusion (over 2 km) particularly on the eastern bank of the Nekor river. They also show a spread of the landfill leachate flow path beyond 1 km in the direction of the groundwater flow (to the North), towards an area of hydrogeological interest located east of the city of Imzouren. These results imply a socioeconomic and environmental vulnerability that evokes an immediate intervention to restore weakened equilibrium.

Geotechnical Terrain Models and Types of Instabilities in the Durmitor Flysch Complex

Abstract The Durmitor flysch complex represents a specific formation both in lithological and engineering geological sense. In the engineering geological sense this lithological formation is characterized by anisotropic and heterogeneous geotechnical properties, which depend on the dominant members within each individual package, as well as their spatial position.The Durmitor flysch complex consists of five superposition bed packages, which are mutually substantially different in their lithological, hydrogeological and geotechnical properties. For the first time in geological literature, this paper distinguishes five types of terrain construction within the Durmitor flysch complex. Contemporary geodynamic processes and their character within the flysch formation are defined. Particular emphasis is put on landslides, which represent a contemporary geodynamic phenomenon with certain specificities.

Fluid Circulations at Structural Intersections through the Toro-Bunyoro Fault System (Albertine Rift, Uganda): A Multidisciplinary Study of a Composite Hydrogeological System

Regional fault structures along rift basins play a crucial role in focusing fluid circulation in the upper crust. The major Toro-Bunyoro fault system, bounding to the east of the Albertine Rift in western Uganda, hosts local fluid outflow zones within the faulted basement rocks, one of which is the Kibiro geothermal prospect. This major fault system represents a reliable example to investigate the hydrogeological properties of such regional faults, including the local structural setting of the fluid outflow zones. This study investigated five sites, where current (i.e., geothermal springs, hydrocarbon seeps) and fossil (i.e., carbonate veins) fluid circulation is recognized. This work used a multidisciplinary approach (structural interpretation of remote sensing images, field work, and geochemistry) to determine the role of the different macroscale structural features that may control each studied fluid outflow zones, as well as the nature and the source of the different fluids. The local macroscale structural setting of each of these sites systematically corresponds to the intersection between the main Toro-Bunyoro fault system and subsidiary oblique structures. Inputs from three types of fluid reservoirs are recognized within this fault-hosted hydrogeological system, with “external basin fluids” (i.e., meteoric waters), “internal basin fluids” (i.e., hydrocarbons and sediment formation waters), and deep-seated crustal fluids. This study therefore documents the complexity of a composite hydrogeological system hosted by a major rift-bounding fault system. Structural intersections act as local relative permeable areas, in which significant economic amounts of fluids preferentially converge and show surface manifestations. The rift-bounding Toro-Bunyoro fault system represents a discontinuous barrier for fluids where intersections with subsidiary oblique structures control preferential outflow zones and channel fluid transfers from the rift shoulder to the basin, and vice versa. Finally, this work contributes to the recognition of structural intersections as prime targets for exploration of fault-controlled geothermal systems.

Quantitative hydro-geophysical analysis of a complex structural karst aquifer in Eastern Saudi Arabia

The Umm er Radhuma (UER) Formation is a major karst aquifer in Saudi Arabia. This study investigated the hydraulic and petrophysical characteristics of the folded UER carbonate aquifer using integrated hydrological and geophysical logging datasets to understand its complex hydraulic setting as well as detect possible water flow. Petrophysical analysis showed that the UER aquifer has three zones with different lithologic and hydraulic properties. The upper zone attains the best properties with average values of 20%, >100 mD, 3.30 × 10−5–1.34 × 10−3 m/s, and 1.49 × 10−3–6.04 × 10−2 m2/s, with respect to effective porosity, permeability, hydraulic conductivity and transmissivity. The gamma-ray logs indicate a good fracture system near the upper zone of the UER Formation. Pumping test measurements of transmissivity, hydraulic conductivity and storage coefficients were matched with those from geophysical logs and found to be within the expected range for confined and leaky aquifers. Hydrogeological properties were mapped to detect possible groundwater flow in relation to the dominant structure. The underground water of the folded UER aquifer was forced along meandering flow patterns from W-E to SW-NE through the anticlinal axes. The integrated approach can be further used to enhance local aquifer models and improve strategies for identifying the most productive zones in similar aquifer systems.

Variability of hydrogeological parameters in the environment of new nuclear power plant in Lithuania

The groundwater flow and radionuclide (3H, 14C and 137Cs) transport model was performed for the model domain of the experiment site near Ignalina nuclear power plant (INPP) in Lithuania assuming that the radionuclides will reach groundwater straight after the new NPP operation begins. The task of the study is to predict the transportation of radionuclide from the hypothetical reactor of the new NPP and perform a sensitivity analysis in order to predict the effects of radiation on the environment. The main focus of attention was the evaluation of ranges of the parameters, such as effective porosity, hydraulic conductivity and dispersivity, mostly influencing the assessment results.The obtained results show that the activity concentration of the modelled radionuclides strongly depends on the hydrogeological properties of the aquifer. The largest variability of activity concentration is established for the radiocarbon determined by the dispersivity and hydraulic conductivity.

Tracking of geological structures and detection of hydrothermal intrusion by geo-electrical methods in the highlands of Bolivia

Oruro city in the Bolivian highlands depends solely on groundwater to supply domestic consumption and irrigation. The top porous aquifer currently exploited is not fully understood in aspects like geometry, hydrogeological properties and interaction with other aquifers in the region. Recent studies detected traces of fractures in the bedrock beneath the porous aquifer; these geological structures seem to be part of a fractured aquifer in contact with thermal sources. The present study aims to fill the gap between those recently detected fractures and the well-mapped fault system to the east of the study area and identify hydrothermal flows by using geo-electrical methods like Electrical Resistivity Tomography and Transient Electromagnetic soundings. Thirteen tomographic lines, placed transversely to the direction of three main faults, were meant to identify prolongations of those structures by tracking distinctive low resistivity in sectors where saline water saturates the subsoil. This type of water is also present in some hot springs near Capachos, where hydrothermal flows discharge under artesian conditions. Two of the investigated faults seem extending to the northwest, in agreement with the expected linkage towards the recently detected fractures. These two faults appear to reach a volcanic formation since the hydrothermal flows, going mainly upwards, align with their strikes. The remaining fault seems not to be connected to any hydrothermal source. The study presents new information, data and interpretations intending to improve the knowledge about the geological structures in a sensitive part of the local aquifer system.

Using Color Coherence Vectors to Evaluate the Performance of Hydrologic Data Assimilation

AbstractAn inadequate characterization of hydrogeological properties can significantly decrease the trustworthiness of subsurface flow and transport model predictions. A variety of data assimilation methods have been proposed in order to estimate hydrogeological parameters from spatially scarce data by incorporating them into the governing physical models. In order to quantify the accuracy of the estimations, several metrics have been used such as Rank Histograms, root‐mean‐square error (RMSE), and Ensemble Spread. However, these commonly used metrics do not regard the spatial correlation of the aquifer's properties. This can cause permeability fields with very different spatial structures to have similar histograms or RMSE. In this paper, we propose an approach based on color coherence vectors (CCV) for evaluating the performance of these estimation methods. CCV is a histogram‐based technique for comparing images that incorporate spatial information. We represent estimated fields as digital three‐channel images and use CCV to compare and quantify the accuracy of estimations. The appealing feature of this technique is that it considers the spatial structure embedded in the estimated fields. The sensitivity of CCV to spatial information makes it a suitable metric for assessing the performance of data assimilation techniques. Under various factors, such as numbers of measurements and structural parameters of the log conductivity field, we compare the performance of CCV with the RMSE.

Thermo-Physical and Geo-Mechanical Characterization of Faulted Carbonate Rock Masses (Valdieri, Italy)

Water in rock masses is a key factor in geo-mechanics, hydrogeology, mining, geo-thermics, and more. It is relevant in interpreting rock mass behavior (e.g., water-rock interaction or slope stability), as well as in defining heat transfer mechanisms. Pointing out the contribution of secondary porosity in increasing advective heat transfer instead of the conduction phenomenon, this study aims to highlight a different thermal response of sound rocks and faulted zones. Moreover, it provides some methodological suggestions to minimize environment disturbance in data collection and a robust interpretation of the results. An interesting outcrop was identified in a carbonate quarry near Valdieri (north-west Italian Alps): it was studied coupling a geo-mechanical and a thermo-physical approach. In particular, geo-mechanical and photogrammetric surveys, InfraRed Thermography (IRT), and Thermal Conductivity (TC) measurements were conducted. The rationale of the research is based on the fact that, when a substantial temperature difference between flowing groundwater and rocks was detected, IRT can reveal information about geo-mechanical and hydrogeological properties of the rock masses such as a degree of fracturing and joint interconnection. A comparative field and laboratory analysis using different devices enabled a more detailed insight providing values in both dry and wet conditions. A different thermal response was highlighted for the cataclastic zone as well. IRT results showed an evident inverse relationship among the number of joints per meter and the detected surface temperature. This is probably caused by the higher water flow within the cataclastic fault zone. Moreover, low fractured portions of the rock mass presented higher cooling rates and conducted heat far more than those with poor geo-mechanical characteristics (difference up to 40%). A negligible ratio between wet and dried thermal conductivity (about 1%) was also detected in lab measurements, which confirmed that primary porosity is not usually relevant in influencing thermal properties of the sound rock.

Geoelectrical parameters for the estimation of hydrogeological properties

Excessive groundwater extraction could cause environmental degradation such as surface water depletion, saltwater intrusion, and many more. Therefore, groundwater should be extracted in sustainable way to avert the harmful consequences. An accurate amount of sustainable groundwater yield can be obtained through the groundwater flow model that has low uncertainty. It is important to incorporate the actual hydrogeological properties into groundwater flow modeling to reduce the uncertainty. The purpose of this study is to estimate hydrogeological properties, namely, hydraulic conductivity (K) and transmissivity (T), by combining the electrical resistivity (ER) and induced polarization (IP) methods into an analytical equation. This study used an analytical equation that relates the geoelectrical parameters to the hydrogeological properties. The ER and IP methods were applied to improve the accuracy of geoelectrical parameters using the ABEM Lund Imaging system. The developed analytical equation was compared with other studies for verification. The results showed that the analytical equation model developed in this study had the lowest error compared to that of other published analytical equation models. Therefore, the combination of the ER and IP methods with a new proposed constant value for the analytical equation increased the accuracy of hydrogeological properties.

Installation of Deep Groundwater Wells as Solution to Water Resources Problem in Panggang Subsystem, Gunungsewu Karst Area, Indonesia

The karst area in Panggang Subsystem, Gunungsewu has specific hydrogeological properties, including predominant epikarst springs with minimal discharge in dry seasons. Since this situation inevitably leads to drought, the installation of deep wells to extract water from deep aquifers is proposed as an alternative solution to water provision. This study determined the location of these wells using general geological and geomorphological surveys, followed by analyzing the results of geophysical measurements. The results showed potential aquifers in the sand layer of tertiary volcanic aquifers under the limestone formation that makes the karst region. Although three borewells were constructed at three different points, only two of them succeeded and are ready for use to meet the clean water needs of the population at the research site.