Hamburg Institute of International Economics

Effective groundwater exploration is fundamental to the identification and assessment of subsurface water resources, particularly in challenging geological conditions. In such cases, conventional drilling-based approaches are costly and provide only limited one-dimensional information for characterizing the three-dimensional subsurface. Hydrogeophysical techniques offer efficient, non-invasive means of imaging the subsurface and can significantly reduce the need for extensive drilling campaigns. Among these, Electrical Resistivity Tomography (ERT) is one of the most widely used geophysical methods for investigating groundwater systems. However, conventional smoothness-constrained ERT inversion often fails to resolve sharp stratigraphic boundaries or represent internal heterogeneity, limiting its effectiveness in complex geological settings. Structural and geostatistical constraints have each been proposed as enhancements, but when applied separately, they often struggle to simultaneously achieve structural accuracy and inversion stability.We introduce a novel inversion strategy that integrates seismic-derived structural horizons with unit-specific geostatistical constraints within the open-source PyGIMLi framework. This approach balances structural alignment and internal heterogeneity by enforcing sharp boundaries and applying region-specific spatial continuity models.This hybrid strategy is evaluated at two glacially influenced groundwater study sites in northern Germany, where complex Quaternary deposits include interbedded sands, tills, and clays. Results demonstrate enhanced delineation of aquifers and aquitards, improved agreement with borehole resistivity logs, and a reduction in inversion artifacts such as over-smoothing or artificial layering. Compared to conventional and single-constraint inversions, the integrated method more effectively resolves thin confining units, anthropogenic disturbances, and laterally variable aquifer geometries with enhanced structural clarity.This framework offers a transferable solution for hydrogeophysical characterization in heterogeneous environments, particularly where seismic or borehole data are available to guide inversion.

For governments, the occurrence of natural disasters creates the opportunity to demonstrate their willingness and competence in providing prompt and efficient disaster aid. A number of studies has investigated the political consequences of providing disaster aid by analyzing the effects of such aid on subsequent election results. However, the findings of these studies have not yielded a coherent picture. This paper makes a contribution to the existing literature by employing high-frequency (daily) survey data on presidential approval. The combination of this data with wildfire data and information on Federal Emergency Management Agency (FEMA) aid approvals and denials reveals that Barack Obama gained in support among survey respondents for whom FEMA aid was approved by the president, while he was not punished for denials of FEMA assistance. We show that this effect is exclusively driven by respondents without party affiliation and that the effect is temporary. • We combine survey data on presidential approval with disaster information on wildfires. • Our analysis is based on low-scaled, high-frequency US data combined with FEMA data. • Individuals receiving disaster aid have a higher probability of presidential approval. • The effect is temporary and largely driven by independent voters.

The transition towards sustainable economic growth has gained increasing attention due to the urgency of the climate crisis and the need to reduce resource dependency. This study examines the relationship between green energy production and green total factor productivity (GTFP), a metric incorporating environmental factors into traditional productivity measures. Using a panel dataset of 221 European NUTS2 regions across 10 sectors from 2009 to 2021, we estimate GTFP through the Malmquist-Luenberger productivity index. Our analysis focuses on green energy production, particularly hydrogen energy, and its potential impact on GTFP by reducing emissions and optimizing resource use. To ensure robustness, we apply an instrumental variable (IV) approach. The results indicate a positive relationship between green energy production and GTFP. While hydrogen energy also exhibits a positive effect, it does not reach statistical significance. However, we find that the interaction between green and hydrogen energy enhances GTFP, suggesting spillover effects between these technologies. These findings offer valuable policy insights, emphasizing the importance of integrating green energy sources into economic growth and reducing emissions while supporting the successful adoption of renewable technologies.

Abstract Partial sealing of surfaces of test specimens is essential for determining direction-dependent water absorption of wood. Preliminary tests with existing sealants showed limited applicability particularly for standardisation. The objective was to find new sealer material. The suitability of four different materials (bitumen, polyurethane acrylic resin, liquid rubber spray, aluminium tape) was investigated. Their sorption capacity and water vapor tightness were determined with an automated sorption balance. The experiments revealed that most of the used sealers were not diffusion-tight or showed outgassing. Only the aluminum tape seems to be suitable.