Local Hydrogeological Conditions Research Articles

Detección de roca intrusiva alterada mediante tomografía de resistividad eléctrica: El caso del área de San Luis, zona central de Panamá

This work investigates the potentiality of the 2D electrical resistivity tomography method to delineate an altered intrusive rock domain. The detection and characterization of such altered domains are crucial to understanding local hydrogeological conditions. Here, the target is the San Luis area, located in the northern part of the Estibaná River watershed, within the Los Santos Province in the central region of the Isthmus of Panama. First, a detailed geological survey was carried out to better constrain the tectonic structures. Then, two geological sections were developed based on two 2D electrical resistivity tomographies. A geoelectrical simulation process was conducted in both sections to set theoretical models whose model responses (synthetic field data set) would be consistent with the observations. After appropriate selection of the inversion parameters by using the Boundless Electrical Resistivity Tomography (BERT) code, the observations were processed, resulting in low calculation errors (2 < 0.51). Based on the superficial geological information and the results of the geophysical modelling, two profiles were established, depicting the lateral and in-depth distribution of rocks and sediments. The limit of the Ocú-Parita fault zone was identified as well. The results of the 2D inversion of the synthetic data, obtained with the established theoretical models, are consistent with the 2D inversion of the observations. Electrical resistivity tomography studies can be useful in establishing groundwater management models, particularly in areas that experience severe water scarcity during the dry season.

Feasibility of riverbank filtration in Vietnam

Riverbank filtration (RBF) could contribute to meeting the growing demand for drinking water in Vietnam. This study investigates the feasibility of implementing RBF in different regions of Vietnam, with a focus on the Red River Delta (RRD) and Binh Dinh (a province in central Vietnam). Although Vietnam’s extensive river network and shallow aquifers generally provide favorable hydrogeological conditions for RBF, regional variations in hydrogeology introduce specific challenges. In the RRD, complex hydrogeological settings, such as thick clay layers near the surface and low hydraulic conductivity in the Holocence aquifer, can limit the effectiveness of RBF in maximizing the portion of bank filtrate and improving water quality. In contrast, Binh Dinh generally presents more favorable conditions, with absence of clay layers on top and higher hydraulic conductivity leading to successful RBF implementation. Water quality issues such as high concentrations of ammonium, arsenic, and other pollutants persist in both RBF and groundwater in the RRD, requiring careful site-specific evaluations. The study also highlights that while surface water remains underutilized compared to groundwater, its use may be economically preferable in regions where groundwater quality is compromised. Lessons learned from the RRD and Binh Dinh can serve as good practice for RBF implementation in other parts of Vietnam. The findings indicate that while RBF holds significant promise for enhancing water supply in Vietnam, its application needs to be carefully tailored to local hydrogeological and water quality conditions.

AI-Driven Groundwater Level Enhancement System using Advanced Prediction Algorithms

This research focuses on predicting water sources in various areas by analyzing historical data on groundwater levels, rainfall, and borewells. The study explores the relationships between groundwater levels and environmental factors, emphasizing the influence of rainfall on aquifer recharge. Borewell data, including depth and water quality, is incorporated to identify potential water sources. The research involves data cleaning, exploratory analysis, and machine learning to predict groundwater levels based on diverse features such as rainfall patterns and geographical characteristics. Spatial analysis using GIS tools visualizes the distribution of groundwater levels and rainfall. The model's performance is evaluated, considering metrics and local hydrogeological conditions, with an emphasis on integrating borewell data. Continuous monitoring and updates ensure the model's ongoing relevance. This integrated approach aims to provide insights for sustainable water resource management, assisting decision-makers in planning water sources in diverse areas.

Hydrogeochemical characteristics and solute sources of groundwater in the Yuhengbei mining area, Shaanxi Province, China

In mining areas, groundwater resources are crucial for providing drinking water, as well as water needed for plant growth and mining. The Yuhengbei mining area is situated in arid and semi-arid areas in Western China. As there are a number of large-scale mining fields in the area, their exploitation may affect both the quality and quantity of groundwater. The hydraulic connection between aquifers directly determines whether deep coal mining activities affect water quality in shallow aquifers. This study investigates the hydrogeochemical characteristics and the solute sources of groundwater (including surface water, Quaternary water, water from Cretaceous and Jurassic coal strata aquifer) in the Yuhengbei mining area. The study uses conventional, multivariate statistical analysis, and dissolved organic matter (DOM) analysis. The results suggest that all water samples were slightly alkaline, while the water from the shallow aquifers (surface water, Quaternary and Cretaceous aquifers) was predominantly of the HCO3-Ca type. Furthermore, the groundwater in the deep Jurassic aquifer was mostly of the SO4-Na type. Major ion and DOM concentrations appeared to decrease with increasing aquifer depth. Moreover, the groundwater circulation is regulated by natural processes. Namely, rock weathering was the main mechanism controlling the chemical constituents of groundwater in the shallow aquifers, while groundwater quality in deep aquifers was mainly governed by the dissolution of evaporation. Water–rock interaction and cation exchange were the main mechanisms controlling the chemical constituents of groundwater. The R-mode HCA revealed that natural processes controlled the chemical composition of groundwater, as well as that the evolution of groundwater is primarily controlled by the nature of the geological structures and the local hydrogeological conditions. The TOC and UV254 results suggest that the coal strata aquifer had a weak hydraulic connection with the overlying aquifers. The DOM was mainly derived from autogenous biological sources. Based on the indicator values, the hydraulic connection between the deep aquifers and the upper shallow aquifers was weak overall. These results show that in this area, although drinking water and irrigation water come predominantly from shallow groundwater, mining activities temporarily have little impact on the quality of shallow groundwater. Better understanding hydrogeochemical characteristics and formation mechanisms will provide a technical basis for local groundwater management and support the sustainable use of water resources.

The challenge of developing ecohydrological metrics for vegetation communities in calcareous fen wetland systems

Calcareous fens are peat-wetlands fed mainly by groundwater, located in topographic hollows and served by springs or seepages of water derived by contact with base-rich mineral ground. In the European Union they are protected habitats requiring special conservation measures. To better understand the environmental supporting conditions of alkaline fen habitat found in Ireland, a 2-years hydrological and hydrochemical monitoring programme was carried out on four contrasting fen sites that covered an ecohydrological gradient representing intact to highly degraded conditions. This paper presents a methodology (and its limitations) of how the evaluation of the temporal and spatial variability of the quality and hydrological dynamics associated with different representative vegetation communities within the four fens can be used to develop ecohydrological metrics for fen habitat. The conditions supporting fen habitat in “good” ecological condition, indicative of a functioning alkaline habitat, were determined and contrasted with conditions found in habitats deemed to be in “poor” ecological condition. Results indicate that an annual water level always above the ground surface within a threshold depth envelope of between 0.030 and 0.28 m is required for at least 60% of the year for healthy fen vegetation. In terms of hydrochemistry, higher concentrations of nutrients were found in the sediments at depth and the groundwater feed compared to the phreatic water table. This suggests the fens may be incorporating the incoming nutrients into their internal biogeochemical cycles and that there is a net accumulation of nutrients within the wetlands. Although envelopes of nutrient concentrations in the surface water of the fen associated with habitat in good ecological condition can be defined (e.g., dissolved reactive phosphorus concentrations of between 6 and 37 µg-P/l for PF1 habitat), these levels should be regarded as the water quality after the fen vegetation has effectively interacted with the higher incoming nutrient levels in the groundwater. Moreover, the local hydrogeological conditions that define groundwater pathways (and associated water quality impacts) in such calcareous fens, allied to the localized nature of these measurements in these field studies, makes it difficult to define groundwater water quality threshold values with any confidence.

Complex 3D Migration and Delayed Triggering of Hydraulic Fracturing‐Induced Seismicity: A Case Study Near Fox Creek, Alberta

AbstractEarthquakes resulting from hydraulic fracturing (HF) can have delayed triggering relative to injection commencement over a varied range of time scales, with the majority of M ≥ 4 mainshocks occurring near/after well completion. This poses serious challenges for risk mitigation and hazard assessment. Here, we document a high‐resolution, three‐dimensional source migration process with delayed mainshock triggering that is controlled by local hydrogeological conditions near Fox Creek, Alberta, Canada. Our results reveal that poroelastic effects might contribute to induced seismicity, but are probably insufficient to activate a large fault segment not critically stressed. The rapid pore‐pressure build‐up from HF can be very localized and capable of producing large, felt earthquakes if adequate hydrological paths exist. We interpret the delayed triggering as a manifestation of pore‐pressure build‐up along pre‐existing faults needed to facilitate seismic failure. Our findings can explain why so few injection operations are seismogenic.

Impact Assessment of Artificial Recharge Structures on Kakatiya University Campus, Warangal Urban District, Telangana

The artificial recharge structures (ARS) project was taken up on Kakatiya University campus, Warangal urban district, Telangana state with the dual purpose of meeting the growing demand for water supply on campus and to demonstrate the benefits of artificial recharge to the students and society at large. Different types of site-specific recharge structures were developed in tune with the local hydrogeological conditions. 9 check dams, 2 mini-percolation tanks (MPT), 2 percolation tanks, 1 Gabion structure, 1 farm pond, and a series of continuous contour trenches, staggered contour trenches, and 69 rooftop rainwater harvesting structures at 19 different buildings were constructed. These structures together contributed 27.62 ham of water to the local aquifer in the year 2013; the estimate is substantiated by applying GEC methodology-1997. The mean water levels have risen by 8.41 m between 2012 and 2014 and a rising trend of 3.05 m is displayed on an average in hydrographs of the observed wells. Efficacy of ARS was visible in terms of feeble adverse effect in 2014 (the change in the head was −0.71 m) despite a deficit rainfall of 42%. Water chemistry displayed a mixed response to induced recharge; cation content was reduced in some samples whereas anions were added in about half of the tested samples. Hydrological properties, together with solute load and absorption-desorption capacity of percolating water, might have led to hydrochemical variability. The locations and appropriate designs enabled to harvest the rainwater in the most effective way leading to a net rise in depth of water levels by 3.24 m and 2.30 m between pre-monsoon of 2012–2013 and 2013–14 respectively. In the post-monsoon season, it was 1.68 m and −3.22 m for the same years (in the 2014 monsoon the area received 171 mm deficit rainfall). Despite poor rainfall in 2014, due to the completion of the ARS scheme, the bore wells yields stabilized at 4.07 lakh liters/day which was about 40% more than the pre-project year, May 2012.

Assessment of Groundwater Resources in Coastal Areas of Pakistan for Sustainable Water Quality Management Using Joint Geophysical and Geochemical Approach: A Case Study

Delineation of fresh/saline groundwater is essential for sustainable water quality management, especially in the coastal areas all around the globe. Seawater intrusion causes substantial degradation in quality of freshwater resources in the coastal areas. The main reason for saltwater intrusion is the changing environment in terms of sea-level rise, climate change, and over-extraction of freshwater resources to meet the growing demands. In this study, an integrated approach of geophysical and geochemical methods was used to assess saltwater intrusion in the coastal areas of Bela Plain, Pakistan. The inverted electrical resistivity computed from 50 vertical electrical sounding (VES) constrained the subsurface into five layers and two aquifers through 3D imaging, such as silty clay and sandy clay containing saline water, and sand, sandy gravel, and gravel containing freshwater. However, the narrow range of resistivity values shows an overlap of saline/fresh groundwater. Such ambiguity in the resistivity interpretation was removed by Dar-Zarrouk (D-Z) parameters. D-Z parameters, namely transverse unit resistance (Tr), longitudinal unit conductance (Sc), and longitudinal resistivity (ρL) estimated from VES, marked a clear distinction between saline and fresh aquifers with a wide range of values. The geochemical method was performed using 20 water samples for the main cations (K+, Ca2+ Na+, and Mg2+), anions (SO42−, HCO3−, Cl−, and NO3−), and other parameters (TDS, EC, and pH). Fresh/saline aquifers revealed by D-Z parameters are in good agreement with those delineated by physicochemical parameters and local hydrogeological conditions. This study delineates seawater intrusion of about 13–42 km from Sonmiani Bay in the Arabian Sea towards the inlands of Bela Plain. Therefore, it is expected that this investigation will be helpful in future planning for the management and exploitation of freshwater resources in the study area. Our study suggests that D-Z parameters can be used as the most inexpensive alternative to the traditional geotechnical and environmental tests for the demarcation of fresh/saline groundwater with a large coverage in any coastal or contaminated area under a homogeneous or heterogeneous setting.

Climate Change Yields Groundwater Warming in Bavaria, Germany

Thermodynamic coupling between atmosphere and ground yields increasing aquifer temperatures as a consequence of global warming. While this is expected to manifest as a gradual warming in groundwater temperature time series, such continuous long-term recordings are scarce. As an alternative, the present work examines the use of repeated temperature-depth profiles of 35 wells in southern Germany, that were logged during campaigns in the early 1990s and in 2019. It is revealed that the temperatures have increased in nearly all cases. We find a moderate to good depth-dependent correlation to trends in air temperature, which however is strongly influenced by local hydrogeological and climate conditions. While during the last three decades, air temperatures have increased by a rate of 0.35 K (10a)-1 on average, the temperature increase in the subsurface is decreasing with depth, with median values of 0.28 K (10a)-1 in 20 m and only of 0.09 K (10a)-1 in 60 m depth. Still, the slow and damped warming of the groundwater bodies are remarkable, especially considering naturally very minor temperature changes in pristine groundwater bodies and predictions of atmospheric temperatures. This entails implications for temperature-dependent ecological and hydro-chemical processes, and also for the heat stored in the shallow ground. Moreover, it is demonstrated that the annual heat gain in the groundwater bodies below 15 m due to climate change is in the range of 10% of the state’s total heat demand, which underlines the geothermal potential associated with the change in natural heat fluxes at the ground surface.

Effect of Water Content on Dynamic Fracture Characteristic of Rock under Impacts

Water contents in rocks vary with local hydrogeological conditions and may significantly affect the stability of rock mass engineering. For example, geological disasters are usually occurring after rainfall, such as landslides, karst collapse. In this paper, drop plate impact (DPI) tests were performed on single cleavage triangle (SCT) red sandstone specimens with dry, natural, absorbed and saturated conditions, which has a great guiding significance for deep understanding of dynamic failure of rock materials. The crack initiation time was obtained by crack propagation gauges (CPGs), and crack propagation speeds were computed by fractal method. The dynamic stress intensity factors (DSIFs) were calculated by ABAQUS code. Meanwhile, the microstructure of the fracture surface was scanned and was analyzed. The results show that the average critical DSIFs and crack propagation speeds vary with water content significantly. For the dry sandstone, the average critical DSIF is the highest, whereas the average crack speed is the lowest. For the natural sandstone, the average critical DSIF is the lowest, whereas the average crack speed is the highest. For the water-bearing sandstone, i.e., the natural, absorbed and saturated sandstone, the average critical DSIF increases with water content, whereas the crack speed decreases with increasing water content.

Land Subsidence due to Leakage of Aquitard-aquifer Pore Water in an Under-construction Tunnel of East-West Metro Railway Project, Kolkata

Palaeo-geographical conditions control the sedimentological and hydrological heterogeneity within the upper aquitard and late Pleistocene aquifers beneath Kolkata. Such complexity at Bowbazar was unmapped prior to the Tunnel Boring Machine (TBM) of East-West metro project which hit the local aquifer at 14 m depth. This led to development of cracks in tens of buildings due to land subsidence; few of which collapsed immediately, and some stood in such a precarious position to be eventually razed. Mass evacuation was undertaken from the area. This paper assesses the local hydrogeological conditions and hydrostatic pressure of the aquitard-aquifer system that caused the disastrous land subsidence.

A 3D Geodatabase for Urban Underground Infrastructures: Implementation and Application to Groundwater Management in Milan Metropolitan Area

The recent rapid increase in urbanization has led to the inclusion of underground spaces in urban planning policies. Among the main subsurface resources, a strong interaction between underground infrastructures and groundwater has emerged in many urban areas in the last few decades. Thus, listing the underground infrastructures is necessary to structure an urban conceptual model for groundwater management needs. Starting from a municipal cartography (Open Data), thus making the procedure replicable, a GIS methodology was proposed to gather all the underground infrastructures into an updatable 3D geodatabase (GDB) for the metropolitan city of Milan (Northern Italy). The underground volumes occupied by three categories of infrastructures were included in the GDB: (a) private car parks, (b) public car parks and (c) subway lines and stations. The application of the GDB allowed estimating the volumes lying below groundwater table in four periods, detected as groundwater minimums or maximums from the piezometric trend reconstructions. Due to groundwater rising or local hydrogeological conditions, the shallowest, non-waterproofed underground infrastructures were flooded in some periods considered. This was evaluated in a specific pilot area and qualitatively confirmed by local press and photographic documentation reviews. The methodology emerged as efficient for urban planning, particularly for urban conceptual models and groundwater management plans definition.

Streamflow depletion from groundwater pumping in contrasting hydrogeological landscapes: Evaluation and sensitivity of a new management tool

Groundwater pumping can reduce streamflow by reducing groundwater discharge and/or inducing streamflow infiltration, which together are referred to as streamflow depletion. Recently, analytical depletion functions (ADFs) have been suggested as rapid and accurate tools for streamflow depletion assessment, but their performance has only been tested in a few hydrogeological settings. To evaluate whether they will be useful tools for other regions with contrasting stream network and hydrogeological characteristics, we compared ADFs to calibrated MODFLOW models in BX Creek and Peace region with distinct hydrogeological settings (interior plateaus & highlands, and boreal plains, respectively) and spatial scales (165 km2 and 1952 km2, respectively) in British Columbia, Canada. Results showed that ADFs can accurately identify most affected streams by pumping for 100% and 83% of wells in the BX Creek and Peace region, respectively, and had small prediction errors compared with MODFLOW. Specifically, the mean absolute error of predicted depletion ranged from 2% to 14% of the highest simulated pumping rate over the study period of 30 years, with improved accuracy during the pumping season. We also found different responses of ADF performance to hydrostratigraphic properties such as hydraulic conductivity, aquifer thickness, streambed conductance, and well depth across two domains, indicating that different factors control ADF accuracy in different hydrogeological settings. Therefore, we conclude that ADFs are useful tools for conjunctive water management, but a good understanding of local hydrogeological conditions is needed to address the potential uncertainty of ADFs for decision-making.

Methods used to construct underwater pile caps on the Hong Kong–Zhuhai–Macao Bridge

The embedded pile-cap design in the Hong Kong–Zhuhai–Macao Bridge project meant that prefabricated pier shafts and pile caps had to be installed under water. This posed a host of daunting construction-related challenges. The designer for the bridge – the Highway Planning and Design Institute, Beijing, China – proposed a method using temporary retaining structures to assist in the underwater installation. According to the local hydrogeological conditions and the capacity of the equipment available in each section, three methods of construction for these temporary works were used. Following completion of the project in 2018, this paper provides a technical comparison of the three methods with the aim that it will serve as a reference for similar projects in the future.

Numerical Simulation of Multi-Water-Source Artificial Recharge of Aquifer: A Case Study of the Mi-Huai-Shun Groundwater Reservoir

Artificial recharge is an effective way to alleviate water shortages and excessive groundwater exploitation. In this study, to explore environmental changes of surface water and groundwater during multi-water-sources recharge process, numerical simulation method was applied. Local reclaimed water, treated by wetland, and water from the South-to-North Water Transfer Project (SNWTP) were used to recharge groundwater reservoir in Mi-Huai-Shun District (Miyun District, Huairou District and Shunyi District). The Flow Model results showed that the accumulated loss of the groundwater resource in the Mi-Huai-Shun area from 2007 to 2016 reached – 1.784 × 109 m3. All the water sources contribute to the recharge of groundwater, raising the groundwater level and increasing the groundwater reserves. Meanwhile, the Solute Transport Model results show that different water source has different effects on the local groundwater environment. chloride concentration of reclaimed water source and wetland water source are higher than groundwater, and the artificial recharge caused the chloride concentration of groundwater in receiving area to rise. The water from the SNWTP played an important role on reducing chloride concentration due to dilution. In addition, Multi-Water-Source artificial recharge is also related to the local hydrogeological conditions. This study provides a comprehensive analysis of the impact of multi-water-source recharge on groundwater quantity and quality.

Developing a novel biofiltration treatment system by coupling high-rate infiltration trench technology with a plug-flow porous-media bioreactor

The sequence of two infiltration steps combined with an intermediate aeration named ‘sequential managed aquifer recharge technology (SMART)’ proved to be a promising approach to replenish groundwater using treated wastewater effluents or impaired surface waters due to efficient inactivation of pathogens and improved removal of many trace organic chemicals. To minimize the physical footprint of such systems and overcome limitations through site-specific heterogeneity at conventional MAR sites, an engineered approach was taken to further advance the SMART concept. This study investigated the establishment of plug-flow conditions in a pilot scale subsurface bioreactor by providing highly controlled hydraulic conditions. Such a system, with a substantially reduced physical footprint in comparison to conventional MAR systems, could be applied independent of local hydrogeological conditions. The desired redox conditions in the bioreactor are achieved by in-situ oxygen delivery, to maintain the homogenous flow conditions and eliminate typical pumping costs. For the time being, this study investigated hydraulic conditions and the initial performance regarding the removal of chemical constituents during baseline operation of the SMARTplus bioreactor. The fit of the observed and simulated breakthrough curves from the pulse injection tracer test indicated successful establishment of plug-flow conditions throughout the bioreactor. The performance data obtained during baseline operation confirmed similar trace organic chemical biotransformation as previously observed in lab- and field-scale MAR systems during travel times of <13 h.

Study of Challenges Faced by Farmers Related to Irrigation Water for Increasing Crop Production

The objective of this study was to evaluate the groundwater scenario in Haveli block of Pune district in Maharashtra, India. An interdisciplinary approach and techniques in both natural and social sciences was used, to unravel how local hydrogeological conditions and institutional arrangements interact and contribute to water problems. The study also attempted to understand the sources of water available for irrigation, methods of irrigation followed by farmers and to suggest how to improve the surface water use for increasing crop yield and area coverage. The study helped to understand the scope for conservation and protection of natural water resources, reduce overexploitation of groundwater and mitigation of water scarcity faced by the community. Fortunately the present government policy encourages the use of micro-irrigation for promoting sustainable agriculture and to cover larger areas under assured irrigation.

Processes of ‘hummocky moraine’ formation in the Gaick, Scotland: insights into the ice‐marginal dynamics of a Younger Dryas plateau icefield

Younger Dryas ice‐marginal (‘hummocky’) moraines in Scotland represent valuable terrestrial archives that can be used to obtain important information on ice‐marginal dynamics and glacier thermal regimes during a period of rapid climatic change. In this paper, we present detailed sedimentological studies of Younger Dryas ice‐marginal moraines in the Gaick, central Scotland, the former site of a spatially restricted plateau icefield. Exposures demonstrate that moraines in the Gaick represent terrestrial ice‐contact fans, with evidence of proglacial and subglacial glaciotectonization, as reported elsewhere in Scotland. The exposures also reveal the influence of local hydrogeological conditions, with pressurization of the groundwater system leading to the formation of hydrofracture fills within some moraines. Clast shape analysis shows that all the moraines contain debris consistent with transport in the subglacial traction zone. The sedimentological data, and the planform arrangement of the moraines as nested arcs or chevrons, indicate that retreat of the Younger Dryas Gaick Icefield outlets was incremental and oscillatory. This evidence strongly suggests a mainly temperate thermal regime and short glacier response times, but with narrow cold‐ice zones near the margins facilitating the elevation of basal debris to the glacier surface. Analogous glaciodynamic regimes occur at modern ice‐cap and plateau icefield outlets in Iceland and Norway, although there are significant differences in the nature of ice‐marginal deposition. The glaciodynamic signature recorded by moraines in the Gaick has allowed us to shed new light on the ice‐marginal dynamics and thermal regime of one of the most easterly Younger Dryas icefields in Scotland.

Seismological and Hydrogeological Controls on New Zealand-Wide Groundwater Level Changes Induced by the 2016 Mw7.8 Kaikōura Earthquake

The 2016 Mw7.8 Kaikōura earthquake induced groundwater level changes throughout New Zealand. Water level changes were recorded at 433 sites in compositionally diverse, young, shallow aquifers, at distances of between 4 and 850 km from the earthquake epicentre. Water level changes are inconsistent with static stress changes but do correlate with peak ground acceleration (PGA). At PGAs exceeding ~2 m/s2, water level changes were predominantly persistent increases. At lower PGAs, there were approximately equal numbers of persistent water level increases and decreases. Shear-induced consolidation is interpreted to be the predominant mechanism causing groundwater changes at accelerations exceeding ~2 m/s2, whereas permeability enhancement is interpreted to predominate at lower levels of ground acceleration. Water level changes occur more frequently north of the epicentre, as a result of the fault’s northward rupture and resulting directivity effects. Local hydrogeological conditions also contributed to the observed responses, with larger water level changes occurring in deeper wells and in well-consolidated rocks at equivalent PGA levels.

Meeting the demand: geothermal heat supply rates for an urban quarter in Germany

Thermal energy for space heating and for domestic hot water use represents about a third of the overall energy demand in Germany. An alternative to non-renewable energy-based heat supply is the implementation of closed and open shallow geothermal systems, such as horizontal ground source heat pump systems, vertical ground source heat pump (vGSHP) systems and groundwater heat pump systems. Based on existing regulations and local hydrogeological conditions, the optimal site-specific system for heat supply has to be identified. In the presented technical feasibility study, various analytical solutions are tested for an urban quarter before and after building refurbishment. Geothermal heat supply rates are evaluated by providing information on the optimal system and the specific shortcomings. Our results show that standard vGSHP systems are even applicable in older and non-refurbished residential areas with a high heat demand using a borehole heat exchanger with a length of 100 m or in conjunction with multiple boreholes. After refurbishment, all studied shallow geothermal systems are able to cover the lowered heat demand. The presented analysis also demonstrates that ideally, various technological variants of geothermal systems should be evaluated for finding the optimal solution for existing, refurbished and newly developed residential areas.