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Karst hydrogeology of Lamprechtsofen (Leoganger Steinberge, Salzburg)

Abstract

The Leoganger Steinberge are a heavily karstified massif largely composed of Dachstein dolomite and limestone hosting the deepest through-trip cave in the world, Lamprechtsofen, whose frontal parts are developed as a show cave. Many parts of this 60 km-long and 1724 m-deep system are hydrologically active. 1.5 km behind the lower cave entrance Grüntopf stream and Kneippklamm stream merge to form the main cave stream. Another underground stream, Stainerhallen stream, flows through the eponymous hall of the show cave. Since 2007 water temperature, electrical conductivity and water level have been monitored in the Grüntopf and Kneippklamm stream. Water temperature and water level in the Stainerhallen and main cave stream have been measured since 2016.

The long-term dataset (2013–2017) shows that the water temperature of the cave streams (Grüntopf stream: 3.7–5.2°C; Kneippklamm stream: 5.1–5.9°C) is largely invariant, but the electrical conductivity varies strongly (Grüntopf stream: 107–210 µS/cm; Kneippklamm stream: 131–248 µS/cm) in response to snowmelt and precipitation events. The event water of the Kneippklamm stream is characterized by a low electrical conductivity and is then followed by slightly warmer and higher mineralized water derived from the phreatic zone. This dual flow pattern also explains the asymmetrical changes of the water level during snowmelt: the fast event water flows directly through vadose pathways to the measurement site, whereas the hydraulic (phreatic) response is delayed. The Grüntopf stream reacts to precipitation and snowmelt events by changes in the karst-water table, which can be explained by a piston flow-model. The Kneippklamm stream reveals evidence of a lifter system.

The altitude of the catchments was calculated using δ18O values of water samples from the underground streams and from surface precipitation. The Grüntopf stream shows the highest mean catchment (2280 m a.s.l.), which is in agreement with its daily fluctuations of the water level until August caused by long-lasting snowmelt. The Stainerhallen stream has the lowest catchment (average 1400 m a.s.l.). The catchments of the other two streams are at intermediate elevations (1770–1920 m a.s.l.). The integration of the catchment analyses and observations from tracer tests conducted in the 1970s showed that the latter reflected only one aspect of the karst water regime in this massif. During times of high recharge the water level rises, new flow paths are activated and the karst watershed shifts.

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Recharge and dynamics of a karst groundwater system in Kakheti (Eastern Georgia)

Abstract

Monitoring temporal variations of 18O and 2H isotopes in precipitation, groundwater and surface water was performed in the region of Kakheti (East Georgia). Data were collected from three meteorological stations at altitudes between 400 - 1,100 m a.s.l., from two shallow and one deep hydrogeological boreholes, and from two surface water monitoring stations (Alazani River and Patmasuri karstic stream). 18O values in precipitation show an annual variation between -22 ‰ and +1 ‰ and a distinct altitude effect. A clear correlation exists between the seasonal isotope composition of precipitation, shallow groundwater and surface water. A five-fold amplitude dampening and a delay of 10-15 days was observed. The data show that precipitation in the Caucasus Mountains to the North infiltrates into the Upper Jurassic - Lower Cretaceous karstic aquifer and travels to the Alazani valley towards south-east. The isotopic signature of winter precipitation is reflected in stream water as well as in shallow groundwater isotope data of groundwater in a 2,000-m-deep hydrogeological borehole at Heretiskari show a distinctly different character with δ18O ranging between -2.8 ‰ to -2.2 ‰ and a deuterium excess of -25 ‰.

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Sandstone petrography and geochemistry of the Nayband Formation (Upper Triassic, Central Iran): Implications for sediment provenance and tectonic setting

Abstract

The Upper Triassic (Norian–Rhaetian) Nayband Formation is situated at the southwestern margin of Central East Iranian Microcontinent and records Eo-Cimmerian events. The formation is composed of mixed carbonate-siliciclastic deposits. This study presents information on the tectonic reconstruction and palaeoclimate of the southwestern margin of Central East Iranian Microcontinent during the Late Triassic. Petrography and modal analyses of sandstones show a variety of quartz-rich petrofacies including subarkose, lithic arkose, sublitharenite, feldspathic litharenite and litharenite. The combined modal analysis and geochemical results of major and trace elements of the sandstone samples represents mixed sedimentary, intermediate, felsic igneous rocks and moderate- to high-grade metamorphic provenance areas. The major elements and modal analyses of the Nayband Formation sandstone samples suggest an active continental margin tec-tonic settings. The palaeoclimatic conditions were sub-humid to humid with relatively low to moderate weathering in the source area which is in agreement with the palaeogeography and palaeotectonic history of southwestern margin of Central East Iranian Microcontinent during the Late Triassic.

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Structural evidence of in-sequence and out-of-sequence thrusting in the Karwendel mountains and the tectonic subdivision of the western Northern Calcareous Alps

Abstract

We present the results of a field study in the Karwendel mountains in the western Northern Calcareous Alps, where we analysed the boundary between two major thrust sheets in detail in a key outcrop where nappe tectonics had been recognized already at the beginning of the 20th century. We use the macroscopic structural record of thrust sheet transport in the footwall and hanging wall of this boundary, such as folds, foliation and faults. In the footwall, competent stratigraphic units tend to preserve a full record of deformation while incompetent units get pervasively overprinted and only document the youngest deformation.

Transport across the thrust persisted throughout the deformation history of the Northern Calcareous Alps from the late Early Cretaceous to the Miocene. As a consequence of transtensive, S-block down strike-slip tectonics, postdating folding of the major thrust, new out-of-sequence thrusts formed that climbed across the step, and ultimately placed units belonging to the footwall of the initial thrust onto its hanging wall.

One of these out-of-sequence thrusts had been used to delimit the uppermost large thrust sheet (Inntal thrust sheet) of the western Northern Calcareous against the next, tectonically deeper, (Lechtal) thrust sheet. Based on the structural geometry of the folded thrust and the age of the youngest sediments below the thrust, we redefine the thrust sheets, and name the combined former Inntal- and part of the Lechtal thrust sheet as the new Karwendel thrust sheet and the former Allgäu- and part of the Lechtal thrust sheet as the new Tannheim thrust sheet.

Open access
Application of the WetSpass simulation model for determining conditions governing the recharge of shallow groundwater in the Poznań Upland, Poland

Abstract

Assessments of the infiltration recharge of groundwater are performed using various methods and on different scales. Infiltration is dependent of climatic factors, aspects of water circulation, as well as on quasi-stationary and variable environmental features of a specific area, which are frequently difficult to determine on the basis of direct measurements or observations. The objective of the present study was to identify factors conditioning recharge of shallow groundwater in selected catchment areas of the Poznań Upland using the WetSpass simulation water balance model with spatially distributed parameters. Our analysis has indicated favourable and unfavourable conditions for recharge of groundwater in the annual period and in both half-year periods, which are the result of mutual relationships between the physical qualities of these catchment areas and their climatic and hydrological characteristics. The results obtained also confirmed the impact of surface runoff and actual evapotranspiration on the spatial distribution of effective infiltration. With soil types and groundwater depth distributions being similar in the catchment areas, changes in relationships between components of water balance are caused by differences in the type of land usage. Application of the WetSpass model has made it possible to arrive at a more accurate assessment of groundwater recharge. The results obtained may be used for erification of recharge areas and values of effective infiltration, set as a boundary condition in groundwater flow models.

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A comparison of the efficiency of riverbank filtration treatments in different types of wells

Abstract

In the paper, a comparison of the efficiency of riverbank treatments is outlined for the Krajkowo well field, where different methods of water abstraction are used. The water is extracted from 29 vertical wells that are located at a distance of 60–80 m from the channel of the River Warta and from a horizontal well with radial drains located 5 m below the bottom of the river. The results of a two-year water-quality investigation indicate that the water quality in both types of abstraction system is influenced by the quality of river water. The water quality observed in the horizontal well is closely similar to that of the river water, with similar concentrations of sulphates, nitrates and micropollutants, but a reduction in bacteriological contamination and plankton is clearly seen. The reduction in contaminants is mainly the result of physical processes, such as mechanical entrapment of suspended material and colloids as well as bacteria and plankton. In the vertical wells, the influence of contamination from river water is also visible, but the reduction in contamination is more significant, especially in cases of bacteria, plankton, micropollutants and nitrates, and is determined by both physical and chemical processes, such as sorption, dissolution, red-ox processes and denitrification. The present research shows that river water treatment is more effective in the case of vertical wells. The most favourable distance of a well from the channel of the river, from the perspective of water quality, is 150–200 m, which corresponds to a residence time of about six months.

Open access
Construction of a numerical groundwater flow model in areas of intense mine drainage, as exemplified by the Olkusz Zinc and Lead Ore Mining Area in southwest Poland

Abstract

Areas of intense mine drainage that are subjected to numerical modelling require the construction of a complex model structure that will properly reflect actual conditions. This paper presents the process and results of constructing such a structure for the Olkusz Zinc and Lead Ore Mining Area, an area situated in a cone of depression the extent of which reaches 500 km2. This size range calls for a selection of appropriate external boundaries, properly separated from these of the mine drainage area. The complex geological structure of the Olkusz area, associated with considerable variation in the thickness of rock formations, discontinuities of rock levels and occurrence of numerous faults, must be schematised so that calculation layers can be identified. The faults in the study area have to be reflected in the regional model structure, although only those faults that actually affect groundwater flows should be selected. The model structure needs to include detailed recognition and reflection of hydraulic contacts between aquifer levels, together with a selection of hydrogeological parameters that are different for particular formations. Only a complex structure built in such a manner may be the foundation of further model studies.

Open access
Open access