Geographic Information System (GIS) as a basis for the  next generation of hydrogeological models to manage  the geothermal area Waiwera (New Zealand)

Kühn, Michael; Präg, Melissa; Becker, Ivy; Hilgers, Christoph; Grafe, Andreas; Kempka, Thomas

doi:10.5194/adgeo-58-31-2022

Cited by 3 publications

(1 citation statement)

References 14 publications

(27 reference statements)

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“…In addition, multiple groundwater production wells will be included in the simulations to represent entire well galleries, with spatially and temporally varying or intermitted pumping rates, as well as receiving water bodies such as rivers and lakes. Further, the equation of state will be extended to account for the effects of the p/T conditions on fluid density and viscosity (Kühn et al, 2022;Otto et al, 2022).…”

Section: Resultsmentioning

confidence: 99%

Upwelling mechanisms of deep saline waters via Quaternary erosion windows considering varying hydrogeological boundary conditions

2022

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Abstract. Intrusion of deep saline waters into freshwater aquifers does not only endanger the regional drinking water supply, but also rivers and stagnant waters and their fauna are threatened by salinisation. The upwelling of highly mineralised saline waters in large parts of the North German Basin is favoured by the presence of Elsterian glacial erosion windows in the Lower Oligocene Rupelian Clay, the most important hydraulic confining unit in this region. Lower precipitation rates and decreasing groundwater levels as a consequence of global climate change, but also anthropogenic interventions, such as increasing extraction rates or the use of the deep geologic subsurface as a reservoir, decrease the pressure potential in the freshwater column and may possibly accelerate this primarily geogenic salinisation process in the coming years. Density-driven flow and transport modelling was performed in the scope of the present study to investigate the upwelling mechanisms of deep saline waters across Quaternary window sediments in the Rupelian. Simulation results show that the interactions between the groundwater recharge rate and anthropogenic interventions such as extraction rates of drinking water wells or the utilisation of the deep subsurface, have a significant influence on the groundwater pressure potential in the freshwater aquifer and associated saltwater upwelling. In all scenarios, salinisation is most severe in the sediments of the erosion windows. Hydraulically conductive faults also intensify salinisation if located nearside erosion windows or induce a more distributed or localised salinisation in aquifers with drinking water relevance in areas that do not intersect with erosion windows. A decline in groundwater recharge thereby significantly favours upward saltwater migration. The simulation scenarios further show that a decrease in groundwater recharge also results in freshwater salinisation occurring up to 10 years earlier, which underlines the need for waterworks to initiate effective countermeasures quickly and in time.

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Section: Resultsmentioning

confidence: 99%

Upwelling mechanisms of deep saline waters via Quaternary erosion windows considering varying hydrogeological boundary conditions

2022

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Numerical simulation of spatial temperature and salinity distribution in the Waiwera geothermal reservoir, New Zealand

Kempka,

Kühn

2023

Grundwasser - Zeitschrift der Fachsektion Hydrogeologie

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The geothermal reservoir in Waiwera was not sustainably managed for many decades. Hence, the responsible authority introduced a water management concept, whereby various independent models were developed and calibrated using observations. As these models were not yet able to reproduce all observations, constant model revisions are critical for efficient reservoir management. Results of a recent field campaign were used for the current model revision, considering two new main structural geological findings to reconstruct the natural reservoir state. Our simulation results demonstrate that a recently proven north-south trending fault in the study area plays a key role in improving the model. Further analysis suggests the presence of a not yet confirmed additional west-east aligned geologic fault in the north, since thermal convection is observed inland. Additional field campaigns are needed to acquire more information on the main geological fault zones as well as additional data on temperature and salinity distributions.

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New data for a model update of the Waiwera geothermal reservoir in New Zealand

Kühn,

Stagpoole,

Viskovic

et al. 2024

Adv. Geosci.

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Abstract. Waiwera is a small coastal village located on New Zealand's North Island above a geothermal reservoir. The origin of the hot water is not well understood. An inferred fault zone at the base of the reservoir is thought to channelise the uprising thermal water. The most recent geological model of Waiwera integrates the depositional environment, mineralogical composition and stratigraphic structures. Coupled numerical fluid flow, heat and transport simulations indicated that further model revisions are required, with support by additional field campaigns, to increase the knowledge of the complex reservoir geology. In this study, gravity data were acquired around the greater Waiwera area. Its interpretation shows a potential fault downthrow in the basement. This feature was tested using a revised geological model in view of a focus for the hot water to rise upwards. The observed characteristic cold and hot water distribution in the system was simulated and the temperature profiles show an improved agreement in the near field around the centre of the reservoir.

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Geographic Information System (GIS) as a basis for the next generation of hydrogeological models to manage the geothermal area Waiwera (New Zealand)

Cited by 3 publications

References 14 publications

Upwelling mechanisms of deep saline waters via Quaternary erosion windows considering varying hydrogeological boundary conditions

Upwelling mechanisms of deep saline waters via Quaternary erosion windows considering varying hydrogeological boundary conditions

Numerical simulation of spatial temperature and salinity distribution in the Waiwera geothermal reservoir, New Zealand

New data for a model update of the Waiwera geothermal reservoir in New Zealand

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