New M@TE! model:

we have provided a summary of your model as a starting point for the README, feel free to edit

Section 1: Summary of your model

Model Submitter:

Dan Sandiford (0000-0002-2207-6837)

Model Creator(s):

• Ben Mather (0000-0003-3566-1557)
• Dietmar Müller (0000-0002-3334-5764)
• Craig O'Neill (0000-0002-6034-1881)
• Adam Beall (0000-0002-7182-1864)
• R.Willem Vervoort (0000-0002-6557-0237)
• Louis-Noel Moresi (0000-0003-3685-174X)

Model name:

mather-2022-groundwater

(this will be the name of the model repository when created)

Model long name:

Constraining the response of continental-scale groundwater flow to climate change

License:

Creative Commons Attribution 4.0 International

Model Category:

• model published in study
• inverse model

Model Status:

• completed

Associated Publication title:

Constraining the response of continental-scale groundwater flow to climate change

Abstract:

Numerical models of groundwater flow play a critical role for water management scenarios under climate extremes. Large-scale models play a key role in determining long range flow pathways from continental interiors to the oceans, yet struggle to simulate the local flow patterns offered by small-scale models. We have developed a highly scalable numerical framework to model continental groundwater flow which capture the intricate flow pathways between deep aquifers and the near-surface. The coupled thermal-hydraulic basin structure is inferred from hydraulic head measurements, recharge estimates from geochemical proxies, and borehole temperature data using a Bayesian framework. We use it to model the deep groundwater flow beneath the Sydney–Gunnedah–Bowen Basin, part of Australia’s largest aquifer system. Coastal aquifers have flow rates of up to 0.3 m/day, and a corresponding groundwater residence time of just 2,000 years. In contrast, our model predicts slow flow rates of 0.005 m/day for inland aquifers, resulting in a groundwater residence time of 400,000 years. Perturbing the model to account for a drop in borehole water levels since 2000, we find that lengthened inland flow pathways depart significantly from pre-2000 streamlines as groundwater is drawn further from recharge zones in a drying climate. Our results illustrate that progressively increasing water extraction from inland aquifers may permanently alter long-range flow pathways. Our open-source modelling approach can be extended to any basin and may help inform policies on the sustainable management of groundwater.

Scientific Keywords:

• groundwater
• thermal-hydraulic
• Bayesian
• water-management

Funder(s):

• NSW Department of Industry
• AuScope (https://ror.org/04s1m4564)

Section 2: your model code, output data

** No embargo on model contents requested****Include model code:**

True

Model code existing URL/DOI:

https://github.com/brmather/Sydney_Basin/tree/master

Model code notes:

In the Scripts folder, HL05 was used to run the optimisation problem and HL06 was used to take the maximum a posteriori model and run it at high resolution.

Include model output data:

True

Model output data notes:

model_output_data contains the following file types:

.h5 - Underworld2 data files .xdmf- Underworld2 xdmf header files .csv - Various data in csv format .npz - data on numpy binary format .png - image files .pvsm - Paraview state files .txt - data in .txt format

Section 3: software framework and compute details

Software Framework DOI/URL:

Found software: Underworld2: Python Geodynamics Modelling for Desktop, HPC and Cloud

Software Repository:

https://github.com/underworldcode/underworld2

Name of primary software framework:

Underworld2: Python Geodynamics Modelling for Desktop, HPC and Cloud

Software & algorithm keywords:

• Python
• C
• finite element
• heat equation
• advection-diffusion

Section 4: web material (for mate.science)

Landing page image:

Filename:

Animation:

Filename:

Graphic abstract:

Filename: fig1.png
Caption: Coupled heat-groundwater flow model of the Sydney–Gunnedah–Bowen Basin based on the MAP estimate of material properties and boundary conditions. (A) Groundwater velocity field with coal seams outlined in grey overlain with temperature gradients measured in boreholes. This visualisation of the velocity field obtained from our model was rendered in 3D using Paraview 5.9 (https://www.paraview.org/). (B) temperature field overlain with heat flux vectors. The 2D slice was generated from our models using Matplotlib 3.4 (https://matplotlib.org/).

Model setup figure:

Filename: figure_2.png
Caption: 3D stratigraphy of the Sydney–Gunnedah–Bowen Basin. The vertical spacing of layers has been exaggerated for visual clarity. The model of the basin was rendered in 3D using Underworld.
Description: In this paper, we apply our numerical framework to the Sydney–Gunnedah–Bowen (SGB) Basin in eastern Australia. The SGB Basin covers about 1.5 million square kilometers, and we model it in high-resolution 3D, using over 10 million cells (or 6 x 6 x 0.6 km, in the x, y, z directions, respectively) to detail flow patterns down to 12 km beneath the crust. By adjusting the model to match real-world data, it provides accurate insights into water and heat movement through deep aquifers in large areas. Temperature advection due to groundwater flow is described by the advection-diffusion equation. Darcy flux is calculated from the groundwater flow equation. Groundwater recharge and discharge are driven by changes in hydraulic head, which is set to the height of the water table at the top boundary surface. The thermal boundary conditions include a constant temperature set to the top boundary, which corresponds to the annual mean surface temperature. The side walls are assigned zero flux, and the bottom temperature boundary is an unknown variable that we invert from borehole temperature data within our Bayesian optimization scheme.