Hydrogeological Changes Research Articles

Genomes of the Orestias pupfish from the Andean Altiplano shed light on their evolutionary history and phylogenetic relationships within Cyprinodontiformes

BackgroundTo unravel the evolutionary history of a complex group, a comprehensive reconstruction of its phylogenetic relationships is crucial. This requires meticulous taxon sampling and careful consideration of multiple characters to ensure a complete and accurate reconstruction. The phylogenetic position of the Orestias genus has been estimated partly on unavailable or incomplete information. As a consequence, it was assigned to the family Cyprindontidae, relating this Andean fish to other geographically distant genera distributed in the Mediterranean, Middle East and North and Central America. In this study, using complete genome sequencing, we aim to clarify the phylogenetic position of Orestias within the Cyprinodontiformes order.ResultsWe sequenced the genome of three Orestias species from the Andean Altiplano. Our analysis revealed that the small genome size in this genus (~ 0.7 Gb) was caused by a contraction in transposable element (TE) content, particularly in DNA elements and short interspersed nuclear elements (SINEs). Using predicted gene sequences, we generated a phylogenetic tree of Cyprinodontiformes using 902 orthologs extracted from all 32 available genomes as well as three outgroup species. We complemented this analysis with a phylogenetic reconstruction and time calibration considering 12 molecular markers (eight nuclear and four mitochondrial genes) and a stratified taxon sampling to consider 198 species of nearly all families and genera of this order. Overall, our results show that phylogenetic closeness is directly related to geographical distance. Importantly, we found that Orestias is not part of the Cyprinodontidae family, and that it is more closely related to the South American fish fauna, being the Fluviphylacidae the closest sister group.ConclusionsThe evolutionary history of the Orestias genus is linked to the South American ichthyofauna and it should no longer be considered a member of the Cyprinodontidae family. Instead, we submit that Orestias belongs to the Orestiidae family, as suggested by Freyhof et al. (2017), and that it is the sister group of the Fluviphylacidae family, distributed in the Amazonian and Orinoco basins. These two groups likely diverged during the Late Eocene concomitant with hydrogeological changes in the South American landscape.

Evaluation of basin-scale hydrogeological changes induced by reservoir operation at the Xiluodu dam site

Impoundment of large-capacity reservoirs has a great impact on groundwater flow in aquifer-aquitard systems. This impact occurs not only at the local scale in the dam area, but also at the regional scale under particular site conditions, causing unexpected geohazards and deformation phenomena. In this study, basin-scale hydrogeological changes induced by reservoir filling and operation at the Xiluodu dam site in southwest China are investigated by hierarchical numerical simulations. Hierarchical groundwater flow models consisting of a basin-scale model (34 km in horizontal dimension) and a site-scale model (4 km) are developed and solved with MODFLOW and a finite element code, respectively, by applying the output of the basin-scale model on the lateral boundaries of the site-scale model. The groundwater level changes in and the groundwater exchange between the confined and unconfined aquifer systems are evaluated. The groundwater level in the confined aquifer has significantly increased by about 96 m beneath the dam site since reservoir filling, and the dimension of the influence zone with an increase over 10 m in groundwater level reaches about 7–9 km in the basin. The rate of vertical leakage from the confined to unconfined aquifer first decreases during the initial filling, and then increases gradually as the pressure propagates into the confined aquifer. It is predicted that the dynamically equilibrated state will be reached in 2027. The local vertical leakage occurring in the plunge pool area along the unplugged boreholes drilled during site investigation is confirmed by a calculation based on the Theis formula. The results are useful for decision-making related to the reservoir operation and safety assessment of the dam.

Remote sensing-based deformation monitoring and geological characterisation of an active deep-seated rock slide (Tellakopf/Cima di Tella, South Tyrol, Italy)

This study presents a 5-year long field campaign combined with 75 years of remote sensing data on the active, deep-seated Tellakopf rock slide in South Tyrol, Italy. Detailed field data and remote sensing techniques from airborne and terrestrial laser scanning (ALS, TLS) and orthoimages from federal flight campaigns and a helicopter-based monitoring campaign, allowed the development of a geometrical-kinematical rock slide model to investigate the initial failure and temporal-variable deformation mechanisms. The rock compound slide formed in foliated, highly fractured metamorphic rock masses at the SE-facing Tellakopf slope, directly above the commuter-rich national road SS 41. A total volume of approximately 3–4 Mm3 was estimated based on geographic information system (GIS) analysis by comparing the pre-failure surface topography and the reconstructed basal shear zone. Multi-temporal deformation analyses based on orthoimages, ALS and TLS data show alarmingly high velocities of at least 9 m/month during the initial formation phase in 2014, followed by a continuous velocity reduction to the current mean annual values of 1–2.5 m/year. Results indicate internal slab formation along discrete shear zones displayed on surface as main and minor scarps. These slabs show a translational movement behaviour along a fully persistent, slightly curvilinear basal shear zone. Rock mass yielding and fracturing conditions extensive mass loss manifested by high rock fall activity and large rock scree deposits at the rock slide toe. The cause for rock slide formation is attributed to retrogressive processes caused by long-term stress release due to topographical and hydrogeological changes by adjacent rock slides.

Agricultural land plot reclamation of citrogypsum sediment pool on Belgorod city territory

One of the main society tasks with the rapid development of industry is assigned to nature protection and correct use of natural resources. Therefore, a significant role is put to the hands of land use. Today, the mining industry in the Russian Federation is characterized by huge volumes of mining. The main production is carried out mainly due to the open method of work. The negative consequences of such developments are: taking of large land areas from the economic turnover, their violation in the course of work; changes in hydrogeology and landscapes; development of erosion processes, etc. Thus, as a result of mining operations, the areas of land disturbed by such developments, processing waste and mucks of rocks are rapidly increasing. Moreover, when mucks are formed, unnecessary rocks are mucked, without taking into account their suitability for reclamation, and when creating external mucks, the requirements of rational farming are not always taken into account. As a result, these lands become barren and negatively affect the environment. It follows from this that lands disturbed by open pit mining must be returned to economic circulation with minimal losses and the creation of favorable conditions for the environment. The work relevance lies in the study of work on the land restoration in quarries during their development and extraction of raw materials for construction purposes. Reclamation provides for the restoration of lands disturbed by quarrying, as well as the preservation of the already restored land.

Dating springlines from hydrogeological and archaeological evidence

AbstractThe relationship between prehistoric populations and water is often poorly understood, partly as a function of historical reliance on qualitative and fragmentary datasets in many regions. Here, we adopt a quantitative approach to analyze a specific aspect of the relationship between prehistoric populations and water for the Cotswold Hills, southwest UK; an area of documented hydrogeological change and extensive Neolithic (ca. 5.5 ka) activity. Using a database of all known Neolithic monuments, we interrogate the significance of water to their habitation. By marshaling a large dataset of recent (ca. 100 years) changes in the discharge and elevation of 259 springs, we establish a striking negative relationship between present-day spring discharge and annual elevation change. We then formulate an inverse problem to predict spring elevations in Neolithic times. Spring elevations are predicted to be closer to, and higher than, Neolithic-dated sites relative to the location of modern springs. These results emphasize a utilitarian and/or reverential link between water and prehistoric populations. Our approach of reconciling markedly different datasets and timescales can easily be adapted to other regions. While groundwater had behaved reasonably predictably since Neolithic times, recent human activity is (and will continue to be) far more significant in influencing groundwater behavior.

Synthetic modeling and field GPR survey to understand the near-surface deformation induced by coseismic groundwater dynamics following the 2019 Mirpur earthquake in Pakistan

The Mirpur earthquake of Mw 5.8 on 24 September 2019 severely damaged villages in the epicentral area. The earthquake-triggered ground dynamics produced widespread liquefaction features on the surface (e.g., fractured road structure and sand boils) and in the shallow subsurface (e.g., elevated groundwater table, fractures, and sand dikes). Due to complexity of liquefaction-induced deformation and timing of field surveys, the structural and hydrogeologic features that develop in the near surface during seismic events are often poorly resolved on ground-penetrating-radar (GPR) profiles. To track and delineate the internal architecture and coseismic changes in groundwater levels and/or pressures due to liquefaction, a GPR survey was carried out soon after the Mirpur earthquake. The sudden pore water pressure changes in the shallow aquifer system caused a rise in the water table via upward groundwater movement and fracturing followed by rapid infiltration. This cascade phenomenon has adverse effects on soil, water resources, civil infrastructure, and public health and safety. To better understand induced changes in the physical properties of road infrastructure and the shallow subsurface, we performed synthetic modeling of electromagnetic wave propagation by employing the finite-difference time-domain method. Based on the available information at multiple scales (borehole and geophysical), subsurface physical models representing the most common and important coseismic features were considered for synthetic modeling. Likewise, synthetic tests of paved road were conducted to simulate the radar response of structural discontinuities (fractures) developed at different angles. To validate synthetic results by identifying a similar dynamic response of the induced hydrogeologic changes in the form of coseismic liquefaction features, a field GPR survey was conducted. Our results clearly demonstrate that the GPR technique is a potential candidate for hydrogeophysical detection and characterization of features of interest in the case of paved roads as well as agricultural and residential areas. Additionally, the successful application of GPR proves it to be a cost-effective, high-resolution, and speedy tool for better assessment of hydrogeologic hazard, socioeconomic consequences, and mitigation in the Mirpur area. The proposed approach may find applications in other seismically active regions around the world.

Groundwater Rise and Associated Flooding in Coastal Settlements Due To Sea‐Level Rise: A Review of Processes and Methods

AbstractCoastal settlements are experiencing the effects of climate change‐induced sea‐level rise, including a significant but often poorly‐characterized impact on groundwater. The shallow water tables present in the built coastal environment contribute to an increased risk from natural hazards such as groundwater flooding and saltwater intrusion. Historical urban development was accompanied by impacts on shallow groundwater, and in the future subsurface environments, including underground infrastructure, will face additional pressure. This article reviews processes of the coastal groundwater zone and simulation tools used to evaluate possible impacts of sea‐level rise. The benefits and limitations of the two main methods to assess coastal groundwater rise and contribution to flooding are discussed using studies and investigations up to 2021. The review addresses challenges associated with the simulation tools to evaluate changes in urban hydrogeology due to sea‐level rise. The models reviewed do not specifically estimate groundwater contribution to land‐surface flooding. We highlight a critical need for methodology comparisons between spatial interpolation and numerical tools that will guide future work. An adequate validation of assessment methods is required and will be supported by improved coastal groundwater monitoring networks focused on water quality, saltwater intrusion, and continuous groundwater levels records. From current monitoring practices, evidence for groundwater rise with rising sea level is not widely observed at present. New monitoring sites are recommended near the coastline and tidally influenced surface water bodies, to better evaluate the rise of the water table and impacts on infrastructure.

An Appraisal of Ground Failure and Hydrogeological Changes Associated with the 28 April 2021 Mw 6 Sonitpur Earthquake, Assam, India, Using Field Evidences and InSAR Measurements

Abstract Widespread damage and coseismic ground disturbances are generally associated with large magnitude and/or shallow focus earthquakes. Surprisingly, a deep focus (34 km), moderate magnitude earthquake (Mw 6) occurred near the Kopili fault zone in Sonitpur district, Assam, India, on 28 April 2021 and created intense ground shaking and extensive damage along the Brahmaputra Valley. We undertook a field survey within a day after the earthquake and carried out Interferometric Synthetic Aperture Radar (InSAR) analysis to map any coseismic ground deformation features. Our field survey revealed extensive liquefaction features and several coseismic secondary ground cracks along the alluvial tracts of the Brahmaputra River system. InSAR analysis revealed a sinistral slip up to ∼60 mm along a north-northwest–south-southeast-oriented previously unmapped lineament or fault. Field investigations revealed coseismic hydrological changes including a sudden rise and fall in the water level by 0.3–0.5 m followed by the injection of sand materials up to a thickness of 1.25 m in dug wells and the appearance of water in seasonally dried river channels and ponds. Interferometric coherence analysis during pre-, co-, and postseismic periods further confirmed the coseismic surge in water at five major tributary rivers of the Brahmaputra River. We speculate that the pressure difference at the shallow unconfined aquifer system of the mountain-front alluvial fan induced by coseismic stresses must have caused channeling of groundwater to the rivers and the contemporaneous water level fluctuations in wells. Amplification of seismic waves at the thick, unconsolidated sedimentary strata of the Brahmaputra Valley could have enhanced the extensive damage due to the 2021 Sonitpur earthquake. The present study has implications in estimating damage potential along the Brahmaputra Valley for future earthquakes.

The AD 1755 Lisbon Earthquake-Tsunami: Seismic source modelling from the analysis of ESI-07 environmental data

This work presents a macroseismic analysis of the AD 1755 Lisbon Earthquake-Tsunami event by means of the combination of intensity data derived from the EMS-98 scale and the ESI-07 scale (Environmental damage). About 600 records of secondary earthquake environmental effects (EEEs) for the whole Spain have been used to define intensities, focused on the SW portion of the Iberian Peninsula. The Spanish data have been complemented with 308 EEEs records from Portugal. The analyses indicate maximum intensities of X EMS-ESI along the Atlantic margin of the Iberian Peninsula with 76 records of Tsunami environmental effects (TEEs). An important amplification (VIII – VII) occurred all along the Guadalquivir basin and the adjacent Betic front at epicentral distances of 300–700 km. In these zones 55 records of ground effects (ground cracks, Liquefactions and slope movements) are catalogued. In the rest of the territory of the Peninsula the most widespread effects were hydrogeological changes with 505 records in Spain and 196 in Portugal (total 701 records) covering all the intensity levels. Increase of flow discharges in springs and elevation of water level in wells was the common groundwater response to seismic shacking, especially in SW Iberia. In this zone water elevation in wells was between 5 and 3 m and persistent increases of discharges long-lasting (several days to two months). Persistent discharges on springs were linked in 143 cases to important SW-NE crustal faults (e.g., Alentejo-Plasencia Fault). From the Intensity distribution the historic seismic scenarios are explored by means of the development of empirical ShakeMaps. These consider the three classical seismic sources proposed for this earthquake: Gorringe Bank (G); Marques de Pombal Fault (M) and Atlantic delamination beneath the Gulf of Cadiz (C). However, individually these seismic sources are too small and unable to generate the resulting seismic scenario depicted by the intensity map developed in this work, with onshore seismic accelerations (PGA) up to 0.82 g. These acceleration values and the great amplification experienced throughout the Guadalquivir basin (0.34–0.52 g) are only possible considering a combination of the three seismic sources (GMC Source) probably related to shallow subduction or lithospheric delamination beneath SW Iberia and the Gulf of Cadiz. This will suggest an NNE-SSW offshore rupture length of 350–360 km with an overall rupture area of c. 84,500 km2 resulting in an event magnitude 8.6 Mw calculated from empirical relationships. The results demonstrate the efficacy of these kind of approaches for better identifying and modelling seismic sources for historical events.

Influence of Hydrogeological Changes on Engineering Geology

Influence of Hydrogeological Changes on Engineering Geology

Conventional and UAV-Based Aerial Surveys for Long-Term Monitoring (1954–2020) of a Highly Active Rock Glacier in Austria

Rock glaciers are creep phenomena of mountain permafrost. Speed-up has been observed on several rock glaciers in recent years and attributed to climate change. Although rare, related long-term studies are nevertheless essential to bring a climate perspective to creep velocity changes. In the present study, we focused on changes both in the surface creep velocity and volume of the Leibnitzkopf rock glacier (Hohe Tauern Range, Austria) in the period 1954–2020. We applied 3D change detection using aerial images of both conventional (12 epochs between 1954 and 2018) and unmanned aerial vehicle (UAV)-based aerial surveys (2 epochs, 2019 and 2020), and combined this with ground and air temperature data. Photogrammetric processing (structure-from-motion, multi-view stereo) of the multi-temporal dataset resulted in high-resolution digital orthophotos/DOPs (5–50 cm spatial resolution) and digital elevation models/DEMs (10–50 cm grid spacing). Georeferencing was supported by five externally triangulated images from 2018, bi-temporal aerial triangulation of the image data relying on stable ground around the rock glacier, measured ground control points (2019 and 2020), and measured camera locations (PPK-GNSS) of the UAV flight in 2020. 2D displacement vectors based on the multi-temporal DOPs and/or DEMs were computed. Accuracy analyses were conducted based on geodetic measurements (2010–2020) and airborne laser scanning data (2009). Our analyses show high multi-annual and inter-annual creep velocity variabilities with maxima between 12 (1974–1981) and 576 cm/year (2019–2020), always detected in the same area of the rock glacier where surface disintegration was first observed in 2018. Our volume change analyses of the entire landform for the period 1954–2018 do not indicate any significant changes. This suggests little permafrost ice melt and/or general low ice content of the rock glacier. Analyses of the temperature data reveal a close relationship between higher temperatures and rock glacier acceleration despite the high probability of low ice content. This suggests that hydrogeological changes play an important role in the rock glacier system. The paper concludes with a summary of technical improvements and recommendations useful for rock glacier monitoring and a general view on the kinematic state of the Leibnitzkopf rock glacier.

Toward Using Seismic Interferometry to Quantify Landscape Mechanical Variations after Earthquakes

ABSTRACT In mountainous terrain, large earthquakes often cause widespread coseismic landsliding as well as hydrological and hydrogeological disturbances. A subsequent transient phase with high landslide rates has also been reported for several earthquakes. Separately, subsurface seismic velocities are frequently observed to drop coseismically and subsequently recover. Consistent with various laboratory work, we hypothesize that the seismic-velocity changes track coseismic damage and progressive recovery of landscape substrate, which modulate landslide hazard and hydrogeological processes, on timescales of months to years. To test this, we analyze the near-surface seismic-velocity variations, obtained with single-station high-frequency (0.5–4 Hz) passive image interferometry, in the epicentral zones of four shallow earthquakes, for which constraints on landslide susceptibility through time exist. In the case of the 1999 Chi-Chi earthquake, detailed landslide mapping allows us to accurately constrain an exponential recovery of landslide susceptibility with a relaxation timescale of about 1 yr, similar to the pattern of recovery of seismic velocities. The 2004 Niigata, 2008 Iwate, and 2015 Gorkha earthquakes have less-resolved constraints on landsliding, but, assuming an exponential recovery, we also find matching relaxation timescales, from ∼0.1 to ∼0.6 yr, for the landslide and seismic recoveries. These observations support our hypothesis and suggest that systematic monitoring of seismic velocities after large earthquakes may help constrain and manage the evolution of landslide hazard in epicentral areas. To achieve this goal, we end by discussing several ways to improve the link between seismic velocity and landscape mechanical properties, specifically by better constraining time-dependent near-surface strength and hydrogeological changes. Hillslopes displaying coseismic surface fissuring and displacement may be an important target for future geotechnical analysis and coupled to passive geophysical investigations.

A Multi‐Hydrogeophysical Study of a Watershed at Kaiwi Coast (Oʻahu, Hawaiʻi), using Seismic Ambient Noise Surface Wave Tomography and Self‐Potential Data

AbstractWe study a watershed containing an old stream valley at the Kaiwi Coast on Oʻahu, Hawaiʻi. The study site has undergone significant hydrogeological changes throughout its history, and at present displays complex interactions of a variety of geological formations. We highlight an innovative and efficient combination of two hydrogeophysical methodologies for studying groundwater systems: ambient noise surface wave tomography (ANSWT), and self‐potential (SP) measurements. We collected (1) 5 days of continuous seismic data, using a total of 54 autonomous seismic nodes, exploiting both ocean wave and traffic noise sources and (2) 386 SP measurements with an average 20 m spacing, in the same area. We showcase how these two data sets complement each other in a joint‐interpretation framework. The SP data display the distribution of groundwater in the region, as well as zones of higher infiltration and/or flow rates. Using ANSWT, we identify the structural contact between the older Koʻolau basalt formation and the younger post‐erosional Honolulu volcanics, as well as the distribution of sedimentary valley fill and coastal deposits. The joint interpretation of the SP and seismic data clearly illustrates that groundwater flow occurs in the identified paleo‐channels at the erosional surface of the basaltic bedrock. Furthermore, it highlights that the basaltic bedrock of the ridges likely forms an important groundwater flow unit. Some flow may occur in the shallower valley fill material. Complementing SP data with seismic data enables us to place groundwater flow inferences, as made from SP data, at depth.

Hydrogeological monitoring of karst activity based on regime observations in the territory of karst lakes

This article shows that the most sensitive indicator of local and regional karst activity in territories of apparent karst processes is the behaviour of karst lakes. The authors propose a hydrogeological monitoring methodology for the karst pro-cess based on the phase-measuring geoelectric control method in the coastal zone of karst lakes. The geoelectric current control of hydrogeological changes in the medium at local levels uses a multi-frequency vertical electric sounding com-bined with a phase-measuring method of registering the geoelectric signal. These proven methods permit to distinguish var-iations of spatial parameters and the electric conductivity of several layers at a time. Moreover, they significantly increase the noise resistance and sensitivity of the measuring system. An adaptive algorithm function of the measuring complex for geoelectric monitoring of karst lakes’ coastal zones was developed to control the operation of facilities and data collection systems. Based on an example of a lake where karst processes are active, the key zones of hydrogeological control were identified depending on karst manifestations. The research confirmed the possibility of local and regional monitoring of the development and forecasting of destructive karst-suffosion processes based on hydrogeological regime observations of karst lakes.

Multilocus phylogeny and historical biogeography of Hypostomus shed light on the processes of fish diversification in La Plata Basin

Distribution history of the widespread Neotropical genus Hypostomus was studied to shed light on the processes that shaped species diversity. We inferred a calibrated phylogeny, ancestral habitat preference, ancestral areas distribution, and the history of dispersal and vicariance events of this genus. The phylogenetic and distribution analyses indicate that Hypostomus species inhabiting La Plata Basin do not form a monophyletic clade, suggesting that several unrelated ancestral species colonized this basin in the Miocene. Dispersal to other rivers of La Plata Basin started about 8 Mya, followed by habitat shifts and an increased rate of cladogenesis. Amazonian Hypostomus species colonized La Plata Basin several times in the Middle Miocene, probably via the Upper Paraná and the Paraguay rivers that acted as dispersal corridors. During the Miocene, La Plata Basin experienced marine incursions, and geomorphological and climatic changes that reconfigured its drainage pattern, driving dispersal and diversification of Hypostomus. The Miocene marine incursion was a strong barrier and its retraction triggered Hypostomus dispersal, increased speciation rate and ecological diversification. The timing of hydrogeological changes in La Plata Basin coincides well with Hypostomus cladogenetic events, indicating that the history of this basin has acted on the diversification of its biota.

Optimal ways to develop ecological and energy-efficient construction

The construction industry has a significant impact on our environment. When erecting buildings and structures, building materials, energy, water and other resources, the production of which violates the ecological balance, are used. The construction process itself has also negative effect on environment and the nearby objects with noise, vibration exposure, waste incineration, groundwater and soil pollution in general. However, the time period required for the construction of the building is insignificant compared to the period of operation. Experts estimate the service life of modern monolithic buildings at 125 - 150 years, and in some cases this index reaches 300 years. During this time, a new problem arises - the ecological balance violation: insufficient insolation, changes in natural wind flows, hydrogeology, vegetation reduction, soil and vegetation layer pollution, air masses stagnation, etc. All this creates the prerequisites for the creation of special environmental protection measures aimed at maintaining ecological balance. Thus, at each stage of the life cycle of a building, it is necessary to carry out the measures to protect the environment and minimize harmful effects on the environment. Today the prerequisites for the green building development are being laid in Russia. The main idea is to reduce energy intensity and increase energy efficiency in construction.

Monitoring after the conclusion of mining works

Abstract After mining works are completed and the mine is permanently closed, the holder of the mining rights must carry out monitoring in accordance with the applicable legislation and for the purpose of controlling the extraction area. This includes monitoring of the changes that have occurred during the process of mining, both on the surface and below it. This article presents an example of a monitoring program after the mining works are completed. The extraction of raw mineral material in an underground mine results in various impacts on the surface and underground space. The areas or segments of monitoring are divided into two parts in this article: The underground part includes monitoring of the geomechanical, climatic, and hydrogeological changes, while monitoring on the surface requires special attention to be paid to the stability conditions of the surface above old mine works and hydrogeological conditions in the area above the extraction or impact area. A practical example of the monitoring program that needs to be made when a mine closes is given in the article. The program covers areas, presents the ways and methods of measurement, as well as reporting of the measurements. The analysis procedure of already existing measurements, which need to be analyzed and included in the preparation of the monitoring program, is also presented.

Hydrogeological Changes along a Fault Zone Caused by Earthquakes in the Moncayo Massif (Iberian Chain, Spain)

The response of springs to earthquakes in the zone of moderate seismicity associated with the fault under study (the Talamantes–Castilruiz fault, Soria, Spain) always leads to a flow decrease regardless of the magnitude of the earthquake and the distance from the epicenter. The sensitivity of the springs is explained by the different degrees of the confinement of their aquifers. The semi-confined aquifer of the Vozmediano spring (1100 L/s) experiences short post-seismic events with a variable decrease in flow and an increase in turbidity, depending on the intensity of the earthquakes felt at the site (Intensity). These changes are likely due to elastic deformation and an increased permeability in their aquifers. This spring is an example of how previous (historical) earthquakes can break the aquifer through the fault causing horizontal movements of the groundwater and displacing the discharge point to a different fracture site located six kilometers from the initial point.

New observations in Central Italy of groundwater responses to the worldwide seismicity

Chemical and physical responses of groundwater to seismicity have been documented for thousands of years. Among the waves produced by earthquakes, Rayleigh waves can spread to great distances and produce hydrogeological perturbations in response to their passage. In this work, the groundwater level, which was continuously recorded in a monitoring well in Central Italy between July 2014 and December 2019, exhibited evident responses to dynamic crustal stress. In detail, 18 sharp variations of the groundwater level due to worldwide Mw ≥ 6.5 earthquakes were observed. Apart from earthquakes that occurred in Papua New Guinea and those with a hypocentral depth > 150 km, all far away Mw ≥ 7.6 earthquakes produced impulsive oscillations of groundwater. As the earthquake magnitude decreased, only some earthquakes with 6.5 ≤ Mw < 7.6 caused groundwater level perturbations, depending on the data acquisition frequency and epicentral distance from the monitoring well. A clear correlation between earthquake distance and magnitude in hydrogeological responses was found. Our results shed light on the hydrosensitivity of the study site and on the characteristics of fractured aquifer systems. Detecting the water table variations induced by distant earthquakes is another step towards a correct identification of (preseismic) hydrogeological changes due to near-field seismicity.

Repeated Subsurface Thermal Profiling to Reveal Temporal Variability in Deep Groundwater Flow Conditions

AbstractReliably quantifying groundwater fluxes to and from confined aquifers in sedimentary basins is increasingly recognized as a critical challenge that impedes sustainable groundwater management. One approach to quantify such fluxes is through the analysis of deep (e.g., &gt;50 m) borehole thermal profiles penetrating through aquifer‐aquitard systems. Recently developed methods to interpret such data exploit the relationship between vertical groundwater flow and the downward propagation of surface temperature disturbances resulting from climate warming. In this note, we advance beyond prior studies that assumed steady‐state groundwater flow by demonstrating how hydrogeological regime shifts on decadal time scales can be quantitatively inferred from temperature‐depth profiles (TDPs). We use a set of repeated temperature‐depth profiles from one site in an unconsolidated sedimentary aquifer system, recorded in 1980 and 2016/2018 to tentatively infer a minimum of a threefold increase in groundwater downwelling to deeper aquifers (i.e., from 100 to 350 mm/year). The enhanced flux likely results from intensified, deep groundwater abstraction in the vicinity since the mid‐1980s. We reach this conclusion through analyzing the occurrence and downward propagation of the minimum temperature in the profiles as well as the temporal trend in deeper groundwater temperatures. We conclude that repeated temperature‐depth profiles can be suitable to archive hydrogeological changes. Our results provide the impetus for more systematic collection of present‐day TDPs to provide a historical benchmark from which to assess future groundwater flow alterations, especially in areas that lack traditional aquifer monitoring via hydraulic head measurements.