scholarly journals Distributed memory parallel computing of three-dimensional variable-density groundwater flow and salt transport

2021 ◽  
pp. 103976
Author(s):  
J. Verkaik ◽  
J. van Engelen ◽  
S. Huizer ◽  
M.F.P. Bierkens ◽  
H.X. Lin ◽  
...  
Keyword(s):  
Parallel Computing ◽  
Groundwater Flow ◽  
Distributed Memory ◽  
Three Dimensional ◽  
Variable Density ◽  
Salt Transport ◽  
Dimensional Variable

Improved parameterization of airborne electromagnetic surveys for groundwater salinity mapping using 3D variable-density groundwater flow models

2020 ◽  
Author(s):  
Jude A. King ◽  
Gualbert H. P. Oude Essink ◽  
Marc F. P. Bierkens
Keyword(s):  
Groundwater Flow ◽  
Initial Conditions ◽  
Regional Distribution ◽  
Variable Density ◽  
Salt Transport ◽  
Inversion Method ◽  
Groundwater Salinity ◽  
Groundwater Model ◽  
Two Factors ◽  
Airborne Electromagnetic

<p>Airborne electromagnetics is a cost-effective and rapid method with which to map the regional distribution of saline groundwater in coastal areas, however the process of transforming observed data into salinity estimates comprises multiple sources of uncertainty. The resulting error primarily relates to two factors: (1) the transformation (or inversion) from airborne observations into physical properties, (2) the availability of lithological information to transform inversion results to salinity estimates. Recent research has shown that this uncertainty can significantly affect the accuracy of resulting groundwater salinity estimates, in particular the location of the fresh-saline interface. Reducing error relating to the two factors is not trivial. Firstly, as the inversion process is non-unique, an infinite number of models can fit the data. Secondly, the availability of lithological information on regional scales is generally low. To highlight potential sources of error and improve parameterization, we investigate the usefulness of combining airborne electromagnetic data with a 3D variable-density groundwater flow and coupled salt transport model. We quantitatively present findings using a synthetic model which was created using an existing large-scale (~100km<sup>2</sup>) 3D groundwater model based on real data from the Netherlands. The model is created in two steps: (1) the available groundwater model is run until a state of equilibrium is reached with the model boundaries and stress terms and (2), an airborne survey is simulated using standard geophysical forward modelling techniques, resulting in set of observations. The airborne observations are then inverted and used alongside a simulated lithological data acquisition programme, which are finally input as initial conditions to a groundwater model. As the groundwater model is assumed to be in a state of equilibrium, we show the effect of implementing an optimization framework that penalizes the rate of groundwater salinity fluctuations by iteratively changing the input parameters of both the inversion method and the lithological data. Results quantitatively highlight the effectiveness of implementing a simple, inter-disciplinary approach to airborne electromagnetic groundwater mapping.</p>

scholarly journals Assessing the Fresh–Saline Groundwater Distribution in the Nile Delta Aquifer Using a 3D Variable-Density Groundwater Flow Model

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1946 ◽  
Author(s):  
Marmar Mabrouk ◽  
Andreja Jonoski ◽  
Gualbert H. P. Oude Essink ◽  
Stefan Uhlenbrook
Keyword(s):  
Groundwater Flow ◽  
Flow Model ◽  
Dynamic Equilibrium ◽  
Nile Delta ◽  
Salt Water ◽  
Three Dimensional ◽  
Variable Density ◽  
Salt Water Intrusion ◽  
Groundwater Flow Model ◽  
Saline Groundwater

The Nile Delta Aquifer (NDA) is threatened by salt water intrusion (SWI). This article demonstrates an approach for identifying critical salinity concentration zones using a three-dimensional (3D) variable-density groundwater flow model in the NDA. An innovative procedure is presented for the delineation of salinity concentration in 2010 by testing different simulation periods. The results confirm the presence of saline groundwater caused by SWI in the north of the NDA. In addition, certain regions in the east and southwest of the NDA show increased salinity concentration levels, possibly due to excessive groundwater extraction and dissolution of marine fractured limestone and shale that form the bedrock underlying the aquifer. The research shows that the NDA is still not in a state of dynamic equilibrium. The modeling instrument can be used for simulating future scenarios of SWI to provide a sustainable adaptation plan for groundwater resource.

Evaluating Freshwater Lens Vulnerability in a Multi-layered, Island Aquifer System in the Tropics

2020 ◽  
Author(s):  
Eddie W. Banks ◽  
Saskia Noorduijn ◽  
Okke Batelaan ◽  
Vincent Post ◽  
Adrian Werner ◽  
...  
Keyword(s):  
Transport Model ◽  
Three Dimensional ◽  
Primary Source ◽  
Variable Density ◽  
Geophysical Data ◽  
Near Surface ◽  
Freshwater Lens ◽  
Calibration Process ◽  
Aquifer System ◽  
Dimensional Variable

<p>Groundwater is the primary source of freshwater supply on remote small islands, where it exists as a freshwater lens. It is extremely vulnerable to over-extraction, pollution and seawater intrusion. Ensuring long-term sustainable management of the groundwater resource is of the utmost importance when there are growing water demands, sea-level rise and/or recharge decline. This study used a three-dimensional, variable-density numerical groundwater flow and solute transport model to investigate vulnerability of a freshwater lens in a multi-layered aquifer system on Milingimbi Island, a small tropical island in northern Australia. The model was used to explore the impacts and possibility of increased groundwater demand on the freshwater lens, its volume, geometry as well as the thickness of the transition zone. The risks of saltwater intrusion, both laterally from the ocean and by localised up-coning from the deeper, more saline aquifers beneath the freshwater lens, were also assessed. Model calibration used observed hydraulic heads and salinity observations from pumping and observation wells. Subsurface bulk conductivity values, which were calculated from inverted airborne electromagnetic (AEM) and near-surface geophysical data, were also used in the calibration process. The results showed that the hydraulic heads and observed salinity achieved the ‘best fit’ in the calibration process, whereas the addition of the geophysical data assisted in constraining the lens geometry in the steady state model and integrated the data poor areas based on traditional hydrogeological datasets. The models’ calibration sensitivity to the range of measured salinities could be enhanced by improving the conversion factor between the AEM-derived conductivity values and the observed salinity data. This would best be accomplished by targeted monitoring wells at discrete depths and locations across the lens and improvements in the sampling/restoration of existing ones. The numerical model provided a framework to evaluate the key underlying hydrogeological processes on the island, as well as an important decision-making tool to ensure a sustainable and reliable water supply for the island community.</p>

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