Influences of hydraulic boundary conditions on the deep fluid flow in a 3D regional model (central Upper Rhine Graben)

Knowledge of groundwater flow is of high relevance for groundwater management or the planning of different subsurface utilizations such as deep geothermal facilities. While numerical models can help to understand the hydrodynamics of the targeted reservoir, their predictive capabilities are limited by the assumptions made in their setup. Among others, the choice of appropriate hydraulic boundary conditions, adopted to represent the regional to local flow dynamics in the simulation run, is of crucial importance for the final modelling result. In this work, we systematically address this problematic in the area of the central part of the Upper Rhine Graben. We quantify how and to which degree different upper boundary conditions and vertical cross-boundary fluid movement influence the calculated deep fluid flow conditions in the area under study. Robust results, which are insensitive to the choice of boundary condition, are: (i) a regional groundwater flow component descending from the graben shoulders to rise at its centre and (ii) the presence of heterogeneous hydraulic potentials at the rift shoulders. Contrarily, results affected by the chosen boundary conditions are: (i) calculated flow velocities, (ii) the absolute position of the upflow axis, and (iii) the evolving local flow dynamics. If, in general, the investigated area is part of a supra-regional flow system—like the central Upper Rhine Graben is part of the entire Upper Rhine Graben—the inflow and outflow across vertical model boundaries need to be considered.

Mapping Transboundary Climate Change Risk: the case study of the Trinational Metropolitan Area Upper Rhine Area

In this study we examine the spatial patterns of risk towards climate change and climatic extremes in the “Trinational Metropolitan Region Upper Rhine” (TMU). Following the concept of risk analysis, we identify the regional dimension of climatic stressors in relation to the socio-economic dimension. We present an indicator-based assessment, which operationalizes risk as a product of its subcomponents climatic stressors, spatial occurrence, sensitivity and impact.We map them individually and aggregate them into a composite index. We also address the specific challenges of the trinational situation, which has an impact on the availability, homogeneity and resolution of comparable data sets. We show that risk can be approximated and mapped despite the uncertainties and additionally we explore to what extent the subcomponents contribute to the overall index. The results show differentiated spatial patterns of risk with cross-border clusters i.e. transnational corridors. Risk is amplified depending on the driving climate scenario for 2021–2050, 2041–2070 and 2071–2100, and increases during the course of the century, especially in the transnational metropolitan corridors of the TMU. Further focus on transnational spatial planning and cooperation is needed in future adaption research and practice.

Characterizing the taxonomic status of Sphingonotus caerulans in the upper Rhine Valley of Alsace (France) (Orthoptera, Acrididae, Oedipodinae)

Sphingonotus is a genus of grasshoppers that contains species groups with several closely related species, among which Sphingonotus caerulans and an unnamed Sphingonotus that are found in continental France. The exact distribution of both species is still under investigation, but it is believed that S. caerulans might be restricted to the northern part of the country, and that Sphingonotus sp. occurs in the southern half and might reach the north east. We explored the genetic identity of Sphingonotus grasshoppers in the upper Rhine Valley of Alsace (northeastern France) using combined fragments of mtDNA ND5 and cytb genes included with other available samples in ML and Bayesian phylogenetic analyses. The results indicate that the five specimens sampled within this region belong to S. caerulans. The actual distribution of Sphingonotus sp. in France remains to be investigated with wider sampling, especially to get a better knowledge on its northern limit.

Citizen Energy Cooperatives in the Upper Rhine Region: Energy Transition and Social Transactions

Based on a sociological fieldwork study (on-site observations, about a hundred interviews and five participatory workshops) in the three French, German and Swiss parts of the Upper Rhine Region (URR), this paper focuses on citizen energy cooperatives through a relational approach (between different actors, between production and consumption, etc.), as pointed out by the literature both in terms of socio-technical systems and of social transactions, including hybridisations when moving from enunciations to practical and territorialised experiences.

Hydro-Thermal Modeling for Geothermal Energy Extraction from Soultz-sous-Forêts, France

The deep geothermal energy project at Soultz-sous-Forêts is located in the Upper Rhine Graben, France. As part of the Multidisciplinary and multi-contact demonstration of EGS exploration and Exploitation Techniques and potentials (MEET) project, this study aimed to evaluate the possibility of extracting higher amounts of energy from the existing industrial infrastructure. To achieve this objective, the effect of reinjecting fluid at lower temperature than the current fluid injection temperature of 70 °C was modeled and the drop in the production wellhead temperature for 100 years of operation was quantified. Two injection-production rate scenarios were considered and compared for their effect on overall production wellhead temperature. For each scenario, reinjection temperatures of 40, 50, and 60 °C were chosen and compared with the 70 °C injection case. For the lower production rate scenario, the results show that the production wellhead temperature is approximately 1–1.5 °C higher than for the higher production rate scenario after 100 years of operation. In conclusion, no significant thermal breakthrough was observed with the applied flow rates and lowered injection temperatures even after 100 years of operation.