groundwater circulation
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2021 ◽  
Author(s):  
Hongbing Tan ◽  
Yu Zhang ◽  
Wenbo Rao ◽  
Hongye Guo ◽  
Wanquan Ta ◽  
...  

2021 ◽  
Vol 18 (2) ◽  
pp. 85-89
Author(s):  
Brajesh K. Dwivedi

The physical and chemical characteristics of spring and well water samples were studied for two years to assess the origin of groundwater and determine the factors driving the geochemical composition. The ionic speciation and mineral dissolution/precipitation were calculated. Water wells, characterising groundwater circulation at shallow depths are moderate to high mineralised waters of Na-HCO3 type. In contrast to the shallow environment, the CO2-rich, deeper water is of the Ca-HCO3-SO4 type and undergoes significant changes in the baseline chemistry along flow lines with increasing residence time. The main factors controlling the groundwater composition and its seasonal variations are the geology, because of the presence of carbonate formations, the elevation and the rate of karst development. In both groups, the carbonate chemistry was a diagnostic approach. The super-saturation with respect to calcite indicates CO2 degassing, occurring either inside the aquifer in open conduits or at the outlet in reservoirs. Interaction between groundwater and surrounding rocks is believed to be the main process responsible for the observed chemical characteristics of groundwater in the study area. Mathematical equations were also derived involving the hydro geological variables for better prediction of the aquifer.


Land ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 441
Author(s):  
Sanja Dugonjić Jovančević ◽  
Josip Rubinić ◽  
Igor Ružić ◽  
Maja Radišić

This research focuses on the analysis of soil-water interaction at the carbonate-flysch contact on the Istrian peninsula in Croatia. As a result of the interaction of surface and groundwater and the position of flysch and carbonate rocks in the geotechnical profile, two problems occur in the study area: numerous instabilities and the occasionally high turbidity of drinking water. As an example, the St. Ivan spring was considered. The paper presents a complex mechanism of groundwater circulation in geological structures at carbonate-flysch contacts, differences in runoff through karst aquifers and flysch rocks during heavy rainfall under current and predicted (climate change) conditions, and the mentioned geohazards as a result of extreme precipitation. The analyses carried out showed the decisive influence of the existing geological structure on the dynamics of infiltration and precipitation runoff, as well as the risks of pronounced spring water turbidity and instability events. The main drivers of these geohazards are continuous long-term precipitation for landslides and intense daily precipitation for turbidity. Possible consequences of climate change are the increase in precipitation intensity, amount and higher variation, which subsequently brings risks such as the increase in maximum runoff, i.e., the expected more frequent occurrence of high turbidity and the more frequent occurrence of higher cumulative precipitation triggering instabilities in the area.


Author(s):  
Vladimir Ignatievich Zui

The territory of Belarus belongs to the western part of the Precambrian East European Platform. Its heat flow pattern is representing by alternating low and high heat flow anomalies. An overwhelming majority of heat flow determinations and in general of geothermal observations in Belarus were fulfilled in boreholes finished in the platform cover. Within the Belarusian Anteclise, Orsha Depression, western slope of the Voronezh Anteclise their bottom holes are typically within the zone of active water exchange, where the groundwater circulation sufficiently influences on recorded thermograms. For instance, observed heat flow density for a number of studied boreholes is low and ranges on average from 15–20 until 35–40 mW/m2 within the Orsha Depression. In a number of studied holes in the northern part of the structure, its values are surprisingly low. They are observed within upper horizons of the zone of active water exchange with pronounced groundwater circulation. Permeable rocks within the geologic section comprise the platform cover with a number of freshwater intervals. Their base is spread here up to depths of 150–250 m. The most of heat flow observations within this area were studied in boreholes which depths is only 200–300 m, sometimes less, as deeper wells are seldom within this geologic structure. Groundwater circulation within loose sediments cools them, most of thermograms here have a concaved shape to the depth axis. As a rule, heat flow values are sufficiently lower in a number of intervals in boreholes finished in the freshwater zone, relatively to the heat flow observed within deeper horizons of the platform cover. In some of studied boreholes, the observed heat flow is as low as 5–15 mW/m2. In most cases it has a tendency to stabilise only at intervals deeper than 600–800 m. It is the main reason for observed low heat flow zones.


Author(s):  
Stefano Segadelli ◽  
Maria Filippini ◽  
Anna Monti ◽  
Fulvio Celico ◽  
Alessandro Gargini

AbstractEstimation of aquifer recharge is key to effective groundwater management and protection. In mountain hard-rock aquifers, the average annual discharge of a spring generally reflects the vertical aquifer recharge over the spring catchment. However, the determination of average annual spring discharge requires expensive and challenging field monitoring. A power-law correlation was previously reported in the literature that would allow quantification of the average annual spring discharge starting from only a few discharge measurements in the low-flow season, in a dry summer climate. The correlation is based upon the Maillet model and was previously derived by a 10-year monitoring program of discharge from springs and streams in hard-rock aquifers composed of siliciclastic and calcareous turbidites that did not have well defined hydrogeologic boundaries. In this research, the same correlation was applied to two ophiolitic (peridotitic) hard-rock aquifers in the Northern Apennines (Northern Italy) with well-defined hydrogeologic boundaries and base-outflow springs. The correlation provided a reliable estimate of the average annual spring discharge thus confirming its effectiveness regardless of bedrock lithology. In the two aquifers studied, the measurable annual outputs (i.e. sum of average annual spring discharges) could be assumed equal to the annual inputs (i.e. vertical recharge) based on the clear-cut aquifer boundaries and a quick groundwater circulation inferable from spring water parameters. Thus, in such setting, the aforementioned correlation also provided an estimate of the annual aquifer recharge allowing the assessment of coefficients of infiltration (i.e. ratio between aquifer recharge and total precipitation) ranging between 10 and 20%.


2021 ◽  
Author(s):  
Severine Moune ◽  
Roberto Moretti ◽  
Arnaud Burtin ◽  
David Jessop ◽  
Tristan Didier ◽  
...  

<p>Fumarolic gas survey of dormant volcanoes is fundamental because the compositional and flux changes in gas emissions are recognised signals of unrest and may even be precursors of eruptions on several dormant volcanoes in hydrothermal unrest [1-5].</p><p>Here we report on the chemical compositions (CO<sub>2</sub>, H<sub>2</sub>S, SO<sub>2</sub>, H<sub>2</sub>) and mass fluxes of fumarolic gas emissions from the low-temperature (from 97° to 104°C) volcanic-hydrothermal system of La Soufrière de Guadeloupe (Lesser Antilles). This present study covers the period 2016 to present, encompassing the peak activity of April 2018. Long-term trends are acquired from both portable MultiGAS measurements (performed monthly) and two permanent MultiGAS stations (4 automated 20’ measurements per day). These MultiGAS data are discussed along with other geochemical and geophysical parameters monitored at OVSG, such as complete fumarole chemistry via Giggenbach bottles, fumarole temperatures, volcanic seismicity and deformation in order to track the deep-sourced magmatic signal contribution compared to the one of the hydrothermal system and detect potential signs of unrest [6].</p><p>Dealing with MultiGAS data from a low-T fumarolic system in a tropical environment is not straightforward due to external forcing effect of meteoric water on gas composition. Hence, interpretation of the observed chemical changes must consider (i) the role of water-gas-rock interactions and gas scrubbing processes by the hydrothermal system and the perched volcanic pond [7], which particularly affect sulphur precipitation and remobilization and (ii) how these processes vary with rainfall and groundwater circulation (i.e. rainy vs non-rainy seasons, extreme events).</p><p>[1] Giggenbach and Sheppard, 1989; [2] Symonds et al., 1994; [3] Hammouya et al., 1998; [4] De Moor et al., 2016; [5] Allard et al., 2014; [6] Moretti et al., submitted; [7] Symonds et al., 2001</p>


2021 ◽  
Author(s):  
Stefano Cara ◽  
Silvana Fais ◽  
Paola Ligas ◽  
Carlo Matzuzzi ◽  
Federica Podda

<p>The aim of this work is to combine geological/geophysical techniques with proximal sensing based on Unmanned Aerial System (UAS) for advanced 3D modeling, in a possible post-mining landscape recovery of abandoned mine sites. In this framework a test area in central Sardinia (Italy) was studied. In this area, several talc-chlorite-feldspar bodies have long been mined in open pit operation greatly modifying the original landscape. At present the rearrangement of the mining site and particularly the open pit works that have been occupied by newly formed pools filled with waters from aquifers can be considered an overall project of landscape recovery. The project team have focused on developing a UAS proximal sensing technique for the acquisition of high-definition digital images and by means of photogrammetric algorithms (CMPMVS) in order to generate a dense 3D point cloud and successively high-resolution digital models (DSM and DTM). The proximal sensing survey was performed at different flight heights to obtain a Ground Sample Distance (GSD) according to the scale of investigation. The availability of a detailed topographic dataset is fundamental to characterize a complex morphology and is a basic support for integration with the data resulting from the geological-geophysical survey conducted in the abandoned mine area. Based on this a geophysical investigation by the electromagnetic very low frequency (VLF) method was carefully planned and carried out to localize potential structural discontinuities that can guide groundwater circulation between the newly formed pools encased in the crystalline basement rocks. The VLF method has a high-resolution power in detecting lateral variations in the electrical properties (i.e., conductivity) of the rock formations related to the presence of underground geological structures. To facilitate the interpretation of the VLF-EM anomalies the Karous–Hjelt linear filter was applied on the EM data. Thanks to the application of this filtering procedure, it was possible to obtain the current density pseudosections along the profiles crossing the basement rocks. The pseudosections provide a representation of the various current concentrations in depth and hence the spatial arrangement of subsurface geological features such as faults, fracture zones and geological contacts. The VLF data were also quantitatively interpreted with a 2D code for the VLF data inversion. Both in the pseudosections and in the 2D resistivity models two main conductive zones are present. These conductive zones could be the signature of a preferential path of the water circulation between the newly formed pools encased in the basement rocks. The application of the integrated geological-geophysical and UAV photogrammetric survey approach proved successful in characterizing the basement rocks of the investigated area and allowed to localize structural discontinuities that can guide the groundwater circulation. The results of this study can represent the indispensable knowledge base to contribute to constraining the hydrogeology numerical model needed for the mine site rehabilitation and reasonable planning of the possible post-mining landscape recovery. The methodological sequence used in this study can be reproduced in other similar abandoned mining sites thus giving an important contribution to an efficient and cost-effective performance of the restoration project.</p>


Author(s):  
Elisa Sacchi ◽  
Emilio Cuoco ◽  
Harald Oster ◽  
Vittorio Paolucci ◽  
Dario Tedesco ◽  
...  

AbstractThe Riardo basin hosts groundwater exploited for the production of high quality, naturally sparkling, bottled water (e.g., Ferrarelle water), and circulating in a system constituted by highly fractured Mesozoic carbonates, overlain by more impervious volcanic rocks of the Roccamonfina complex. The two formations are locally in hydraulic connection and dislocated by deep-rooted faults. The study aimed at elucidating groundwater origin and circulation, using isotopic tracers (δ18O, δ2H, δ11B and 87Sr/86Sr) coupled to groundwater dating (Tritium, CFCs and SF6). Besides recharge by local precipitation over the Riardo hydrogeological basin, stable isotope ratios in water indicated an extra-basin recharge, likely from the elevated surrounding carbonate reliefs (e.g., Maggiore and Matese Mts.). The mineralization process, promoted by the deep CO2 flux, controls the B and Sr contents. However, their isotopic ratios did not allow discriminating between circulation in the volcanic and in the carbonate aquifers, as in the latter the isotopic composition differed from the original marine signature. Groundwater model ages ranged from ~ 30 years for the volcanic endmember to > 70 years for the deep, mineralized end-member, with longer circuits recharged at higher elevations. Overall, the results of this study were particularly relevant for mineral water exploitation. A recharge from outside the hydrogeological basin could be evidenced, especially for the more mineralized and valuable groundwater, and an active recent recharge was detected for the whole Riardo system. Both findings will contribute to the refinement of the hydrogeological model and water budget, and to a sustainable development of the resource.


2021 ◽  
Vol 80 (5) ◽  
Author(s):  
Stefan Scheidler ◽  
Peter Huggenberger ◽  
Horst Dresmann ◽  
Adrian Auckenthaler ◽  
Jannis Epting

AbstractIn regional scale aquifers in the Rhine Valley and Tabular Jura east of Basel (Switzerland), the groundwater circulation was investigated using regional-scale geological and hydraulic 3D models. The main aquifers in the area comprise the Quaternary aquifer of unconsolidated gravel deposits along the River Rhine and its tributaries, as well as the regional scale karst aquifer within the Upper Muschelkalk. Land subsidence, a process likely associated with salt solution mining, indicates further subordinate groundwater bearing segments and complex groundwater interactions along fault zones. In the aquifer systems we investigated, regional-scale groundwater circulation was simulated and visualized in relation to the geological settings. Lithostratigraphic units and fault structures were parameterized and analyzed, including the sensitivity of hydraulic properties and boundaries. Scenario calculations were used to investigate the sensitivity that the aquifer systems had to hydraulic parameter changes during Quaternary aggradation and degradation in the main valley. Those calculations were also done for base-level changes in the Rivers Rhine and Birs. For this purpose, this study considered probable historic base-levels before river regulation occurred, and before river dams and power plants were constructed. We also focused on scenarios considering increased groundwater recharge rates, e.g. due to exceptional long-lasting precipitation, or heavy rainfall events in the catchment area. Our results indicate that increased groundwater recharge rates in the catchment areas during such events (or periods) are associated with orders of magnitude increases of regional inflow into the Upper Muschelkalk karst aquifer. Furthermore, the groundwater fluctuations and groundwater saturated regions within the karst aquifer shift to places where high densities of sinkholes are documented. When the surface water base-levels adapt to probable historic levels, it leads to increased hydraulic gradients (i.e. local lowering of the groundwater level by up to 7 m). Those increased gradients are associated with increased groundwater flow within some aquifer regions that are particularly prone to karst development.


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