The southeastern border of the Upper Rhine Graben: a 3D geological model and its importance for tectonics and groundwater flow

A 3D geological model of the area east of Basel on the southeastern border of the Upper Rhine Graben, consisting of 47 faults and six stratigraphic horizons relevant for groundwater flow, was developed using borehole data, geological maps, geological cross sections, and outcrop data. This model provides new insight into the discussions about the kinematics of the area between the southeastern border of the Upper Rhine Graben and the Tabular Jura east of Basel. A 3D analysis showed that both thin-skinned and thick-skinned tectonic elements occur in the modeled area and that the Anticline and a series of narrow graben structures developed simultaneously during an extensional stress-field varying from E-W to SSE-NNW, which lasted from the Middle Eocene to Late Oligocene. In a new approach the faults and horizons of the 3D geological model were transferred into discrete elements with distributed hydrogeological properties in order to simulate the 3D groundwater flow regime within the modeled aquifers. A three-layer approach with a horizontal regularly spaced grid combined with an irregular property distribution of transmissivity in depth permitted the piezometric head of the steady-state model to be automatically calibrated to corresponding measurements using more than 200 piezometers. Groundwater modeling results demonstrated that large-scale industrial pumping affected the groundwater flow field in the Upper Muschelkalk aquifer at distances of up to 2km to the south. The results of this research will act as the basis for further model developments, including salt dissolution and solute transport in the area, and may ultimately help to provide predictions for widespread land subsidence risk

Tail Risk Hedging and Regime Switching

In this paper, we analyze futures-based hedging strategies which minimize tail risk measured by Value-at-Risk (VaR) and Conditional-Value-at-Risk (CVaR). In par- ticular, we first deduce general characterizations of VaR- and CVaR-minimal hedging policies from results on quantile derivatives. We then derive first-order conditions for tail-risk-minimal hedging in mixture and regime-switching (RS) models. Using cross hedging examples, we show that CVaR-minimal hedging can noticeably deviate from standard minimum-variance hedging if the return data exhibit nonelliptical features. In our examples, we find an increase in hedging amounts if RS models identify a joint crash scenario and we confirm a reduction in tail risk using empirical and EVT-based risk estimators. These results imply that switching from minimum-variance to CVaR- minimal hedging can cut losses during financial crises and reduce capital requirements for institutional investors

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

VaR- and CVaR-minimal futures Hedging Strategies: An Analytical Approach

Although Value at Risk (VaR) and Conditional Value at Risk (CVaR) have been established as standard techniques in many fields of risk management and portfolio selection, the literature rarely applies these risk measures to futures hedging. The purpose of this paper is to characterize analytically VaR- and CVaR-minimal hedging strategies. We apply results about quantile derivatives to obtain first order conditions that hold under weak assumptions on the underlying return distribution. We then focus on conditionally elliptical return processes, which enables us to derive closed form expressions for these conditions. In the case of hedging with a single futures contract, these expressions can explicitly be solved for (C)VaR-minimal hedge ratios. Hedging strategies based on these results account for the risk caused by the fat tails of return distributions. In a further step, we extend our characterizations of optimal hedging strategies to mixtures of elliptical distributions. This generalization allows capturing distributional asymmetries, which was found to be highly important for tail based risk measurement. Overall, our findings can be used to implement (C)VaR-minimal hedging rules for most econometric models employed in the futures hedging literature, including multivariate GARCH and regime switching models

Effects of tunneling on groundwater flow and swelling of clay-sulfate rocks

[1] Swelling of clay-sulfate rocks is a major threat in tunneling. It is triggered by the transformation of the sulfate mineral anhydrite into gypsum as a result of water inflow in anhydrite-containing layers after tunnel excavation. The present study investigates the hydraulic effects of tunneling on groundwater flow and analyzes how hydraulic changes caused by excavation lead to water inflow into anhydrite-containing layers in the tunnel area. Numerical groundwater models are used to conduct scenario simulations that allow one to relate hydrogeological conditions to rock swelling. The influence of the topographic setting, the excavation-damaged zone around the tunnel, the sealing effect of the tunnel liner, and the geological configuration are analyzed separately. The analysis is performed for synthetic situations and is complemented by a case study from a tunnel in Switzerland. The results illustrate the importance of geological and hydraulic information when assessing the risk of swelling at an actual site

Risikoorientierte Bewilligung von Erdwärmesonden

Zusammenfassung: Die Zahl an Erdwärmesonden nimmt in ganz Europa stetig zu. Wie mit anderen Technologien der Energiegewinnung sind auch mit Erdwärmesonden Risiken verbunden. Deshalb bedarf es Leitlinien als Grundlage für die Bewilligungsverfahren, die den Bau und Betrieb einer solchen Anlage regeln. Um dabei den zu erwartenden Nutzen gegen mögliche Risiken abwägen zu können, sind Kenntnisse über die hydrogeologischen Verhältnisse am Standort und die dort stattfindenden Prozesse erforderlich. Am Beispiel des Erdwärmenutzungskonzepts des Kantons Basel-Landschaft wird gezeigt, wie die Bewilligung von Erdwärmesonden differenziert geregelt werden kann, und wie die geologischen Merkmale einer Region in ein Erdwärmenutzungskonzept integriert werden können. Dabei werden insbesondere Karstgebiete, Gebiete mit der Gefahr des Gebirgsquellens und der Subrosion, Gewässerschutzbereiche, und Gebiete mit Grundwasserstockwerkbau oder gespannten Grundwasserverhältnissen berücksichtigt. Der Artikel will damit einen Beitrag zur derzeit stattfindenden gesellschaftlichen Diskussion über den Nutzen und die Risiken der untiefen Geothermie leisten, indem er Risiken durch den Bau und Betrieb von Erdwärmesonden beschreibt, und Möglichkeiten aufzeigt, diese Risiken in der Bewilligungspraxis zu berücksichtige

Effects of tectonic structures, salt solution mining, and density-driven groundwater hydraulics on evaporite dissolution (Switzerland)

Subsurface dissolution (subrosion) of evaporites such as halite and gypsum can lead to extensive land subsidence. Recent land subsidences have been surveyed at six separate locations in northwestern Switzerland. The diameters of the affected surface areas range from 100 to 1,500 m, and corresponding subsidence rates reached more than 100 mm/year. Based on a geometrical model, three sites could be outlined where land subsidence can likely be attributed to salt solution mining. The effects of increased hydrostatic gradient due to both groundwater withdrawal and fluid density contrasts were evaluated in more detail for the remaining sites with a series of 2D density-coupled solute-transport simulations along an approximately 1,000-m-long and 150-m-deep 2D cross section. Simulation results indicate that the upconing process of saline groundwater into the main aquifer occurs under different distributions of subsurface parameters and hydraulic boundary conditions. For the presented setup, the simulations also revealed that the most sensitive factor for the dissolution rate is the structure or dip of the halite formation, which leads to an increase of dissolution rate with increasing dip. Due to the increased density of the brine, an intrinsic flow dynamic develops which follows the direction of the di

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