Concepts for the sustainable management of multi-scale flow systems: the groundwater system within the Laufen Basin, Switzerland

Many groundwater systems consist of multi-scale aquifer units. The exchange processes and rates between these aquifer units are complex. In order to manage such complex systems, a subdivision into different catchments, sub-catchments or groundwater bodies as manageable units is required. The sustainable management of water resources requires a comprehensive view of water-quality and water-quantity aspects not only for water supply issues, but generally also for flood protection and riverine ecosystem functions. Such transformations require an improved understanding of recharge and exchange processes between different aquifer units as well as aquifer-surface water interaction-processes at different spatiotemporal scales. The main objective of this study is to illustrate concepts by defining the geometry and scales of different aquifer units within a sedimentary basin. The Laufen Basin in the Jura Mountains represents a sub-catchment of the River Birs (Switzerland). Its structure is characterized by a pronounced local relief and a series of aquifer units which are typical for many complex groundwater systems in front of mountain chains such as the alpine foreland and the Jura Mountains of Central Europe. A combination of different concepts is required to understand multi-scale flow systems and to describe the various hydrogeological processes. Three concepts are proposed for the Laufen Basin, including: (1) a regional flow-system analysis, based on the concept of hierarchical groundwater flow systems; (2) the river-corridor concept for understanding aquifer-surface water interaction processes; and (3) the calculation of the dynamic vulnerability index and the aquifer base gradient approach for karst flow and fractured flow system

Faecal Indicator Bacteria: Groundwater Dynamics and Transport Following Precipitation and River Water Infiltration

Faecal contamination of drinking water extracted from alluvial aquifers can lead to severe problems. River water infiltration can be a hazard for extraction wells located nearby, especially during high discharge events. The high dimensionality of river-groundwater interaction and the many factors affecting bacterial survival and transport in groundwater make a simple assessment of actual water quality difficult. The identification of proxy indicators for river water infiltration and bacterial contamination is an important step in managing groundwater resources and hazard assessment. The time resolution of microbial monitoring studies is often too low to establish this relationship. A proxy-based approach in such highly dynamic systems requires in-depth knowledge of the relationship between the variable of interest, e.g. river water infiltration, and its proxy indicator. In this study, continuously recorded physico-chemical parameters (temperature, electrical conductivity, turbidity, spectral absorption coefficient, particle density) were compared to the counts for faecal indicator bacteria, Escherichia coli and Enterococcus sp. obtained from intermittent sampling. Sampling for faecal indicator bacteria was conducted on two temporal scales: (a) routine bi-weekly monitoring over a month and (b) intense (bi-hourly) event-based sampling over 3 days triggered by a high discharge event. Both sampling set-ups showed that the highest bacterial concentrations occurred in the river. E. coli and Enterococcus sp. concentrations decreased with time and length of flow path in the aquifer. The event-based sampling was able to demonstrate differences in bacterial removal between clusters of observation wells linked to aquifer composition. Although no individual proxy indicator for bacterial contamination could be established, it was shown that a combined approach based on time-series of physico-chemical parameters could be used to assess river water infiltration as a hazard for drinking water quality managemen

Single blind randomized Phase III trial to investigate the benefit of a focal lesion ablative microboost in prostate cancer (FLAME-trial): study protocol for a randomized controlled trial

Background: The treatment results of external beam radiotherapy for intermediate and high risk prostate cancer patients are insufficient with five-year biochemical relapse rates of approximately 35%. Several randomized trials have shown that dose escalation to the entire prostate improves biochemical disease free survival. However, further dose escalation to the whole gland is limited due to an unacceptable high risk of acute and late toxicity. Moreover, local recurrences often originate at the location of the macroscopic tumor, so boosting the radiation dose at the macroscopic tumor within the prostate might increase local control. A reduction of distant metastases and improved survival can be expected by reducing local failure. The aim of this study is to investigate the benefit of an ablative microboost to the macroscopic tumor within the prostate in patients treated with external beam radiotherapy for prostate cancer.Methods/Design: The FLAME-trial (Focal Lesion Ablative Microboost in prostatE cancer) is a single blind randomized controlled phase III trial. We aim to include 566 patients (283 per treatment arm) with intermediate or high risk adenocarcinoma of the prostate who are scheduled for external beam radiotherapy using fiducial markers for position verification. With this number of patients, the expected increase in five-year freedom from biochemical failure rate of 10% can be detected with a power of 80%. Patients allocated to the standard arm receive a dose of 77 Gy in 35 fractions to the entire prostate and patients in the experimental arm receive 77 Gy to the entire prostate and an additional integrated microboost to the macroscopic tumor of 95 Gy in 35 fractions. The secondary outcome measures include treatment-related toxicity, quality of life and disease-specific survival. Furthermore, by localizing the recurrent tumors within the prostate during follow-up and correlating this with the delivered dose, we can obtain accurate dose-effect information for both the macroscopic tumor and subclinical disease in prostate cancer. The rationale, study design and the first 50 patients included are described.Biological, physical and clinical aspects of cancer treatment with ionising radiatio

Tools to simulate changes in hydraulic flow systems in complex geologic settings affected by tunnel excavation

Geotechnical problems during and after tunnel construction are often related to groundwater circulation. In tunnelling projects, however, groundwater flow systems are often only partly known. This uncertainty is manifested by the typically scarce hydraulic data that limits the understanding of subsurface hydrogeological processes. In particular, there is a general lack of data documenting groundwater flow changes caused by tunnelling. The present paper presents a concept involving an iterative understanding of subsurface hydrogeological systems influenced by tunnelling. A major challenge of our approach consists of integrating complex geological geometries from a 3D geological model (GOCAD) into a numerical groundwater flow model (COMSOL Multiphysics). The starting point is a 3D geological model representing a regional tectonic system located in the Jura Mountains in Switzerland. This geological model is transferred into regional and local-scale groundwater flow models. Due to the lack of hydrogeological data, a 3D view of geological–hydrogeological systems is often required to respond to groundwater-induced geotechnical problems in tunnelling. Numerical groundwater flow models make it possible to perform sensitivity analysis and to test how boundary conditions and hydraulic property distributions influence calculated groundwater flow regimes. In addition, our approach enables testing the effects of changes of hydraulic regimes due to tunnel excavation at different scales

Swelling potential of clay-sulfate rocks in tunneling in complex geological settings and impact of hydraulic measures assessed by 3D groundwater modeling

Swelling of clay-sulfate rocks is a feared problem in tunneling in such rock, causing heave of the tunnel invert and leading to swelling pressures that seriously damage the tunnel lining. Prediction of the swelling potential of rocks in different tunnel sections and tools to evaluate measures that aim at reducing the swelling risk would be a major aid for designers of tunneling projects and rehabilitation works in order to respond adequately to the swelling problem. The study presents a hydrogeological approach to assess the swelling potential of clay-sulfate rocks in tunneling, using the Belchen tunnel in Switzerland as a case study. It shows that this approach can be applied to complex geological settings using structurally consistent 3D numerical models to simulate groundwater flow influenced by tunneling. The models are in particular used to evaluate hydraulic measures that aim at preventing or minimizing water inflow into clay-sulfate rocks after tunneling. Analyzed hydraulic measures include pumping shafts connected to the tunnel drainage, sealing structures applied to the rock zone around the tunnel damaged by the excavation process (excavation damaged zone), as well as groundwater level drawdown in aquifers crossing the tunnel. A sensitivity study addresses model uncertainties and evaluates the impact of model parameters on the swelling potential. Promising measures include the installation of pumping shafts in tunnel sections of clay-sulfate rocks at the border to aquifers and permeable fault zones. The study shows that monitoring of hydraulic heads as well as of groundwater volumes drained by the tunnel would increase the predictive capability of the models. Presented results are site specific. However, the approach to assess the swelling potential of clay-sulfate rocks in tunneling, and to assess hydraulic measures to respond to the swelling problem, can be transferred to other tunneling projects. (C) 2017 Elsevier B.V. All rights reserved

Regional groundwater flow and karst evolution-theoretical approach and example from Switzerland

In 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

Geothermal use of an Alpine aquifer - Davos pilot study

Topographically induced Alpine regional groundwater flow systems below the unconsolidated valley fillings constitute a substantial unused geothermal resource. Within the framework of the INTERREG VB project GRETA (shallow geothermal energy in the Alpine region), we developed a method to quantify the groundwater flux of complex alpine aquifers. The basis of the study is a regional-scale hydraulic groundwater model, which is based on a 3D tectonic model of the Davos region in Switzerland. Based on data from a large pumping test, we were able to calibrate the hydraulic model and to calculate basics for various usage scenarios of energetic exploitation for the Arosa Dolomite aquifer. Favourable conditions for an energetic exploitation are related to large-scale topography differences between groundwater recharge and potential exfiltration areas in the valleys, thanks to the 3D geometry of the large-area tectonic nappe units with their root zone located within river valleys. In general, the proposed concept could be applied to manifold similar geological and hydrogeological settings of the Alpine belt

A 3D spatial planning tool – application examples from the Basel region

The Swiss contribution to the EU project “GeORG” (www.geopotenziale.eu) is the geological 3D-model of the Basel region (600 km2). The 3D-model was developed as a flexible tool for subsurface planning to account for the diversity of subjects which require detailed geological information of the subsurface in densely urbanized areas.  The designed modular data management combines database, 3D-modeling and GIS. During the last years environmental agencies and engineering departments have acknowledged the advantage of such a planning tool. The possibility to flexibly generate exports and to combine hydro-geological information with infrastructural data for a detailed analysis gave rise to repeated requests concerning local subsurface development issues. Two examples illustrate the successful application of the tool: In cooperation with the Canton Basel-Landschaft a map was developed showing the general possibilities for the installation of heat-pumps. This multi-layer GIS map contains surface and subsurface information. For example, it delineates land-use data as groundwater protection areas and information extracted from the geological 3D-model as fault zones or units containing salt or anhydrite. During the planning of a highway tunnel below the city of Basel the 3D-tool aided to find a layout of the tunnel road and to avoid use conflicts with existing subsurface installations. Furthermore, data-gaps and potential geological and hydrological risks could be identified in an early planning phase. This allows planning security-precautions for the construction site more accurately and to prevent unexpected hazards after completion of the tunnel