Oral Presentation Australasian Groundwater Conference 2017

A water balance model for the prediction of groundwater levels adjacent to Fortescue Marsh (#172)

Jinquan Wu 1 , Tim Wilkinson 1 , Jordin Barclay 1 , Fuli Wang 1 , Andrew Brooker 1 , Paul Ricketts 1 , Chris Oppenheim 1
  1. Fortescue Metals Group Limited (FMGL), East Perth, WA, Australia

Effective management of water resources is fundamental to the sustainability of Fortescue’s operations, the environment and, most importantly, the communities within which the business operates. Adjacent to Fortescue’s Chichester Hub operations, the Fortescue Marsh is a wetland of national significance and is considered to be a unique wetland form in Western Australia.

A water balance model has been developed for estimation of baseline groundwater levels (GWL) at monitoring bores on the northern fringe of the Fortescue Marsh. The water balance model uses historical weather data and temporal marsh surface water level (SWL).  Marsh SWLs were either derived from satellite images or reconstructed from a flood area model using climate data (Rouillard, et al., 2014). The near marsh monitoring bores were installed to provide early warnings for water level changes near the marsh.  Baseline GWLs at the monitoring bores are required for establishing trigger levels, which take account of climatic variability.

The model consists of four major modules:

  1. A nonlinear depth-dependent module for estimating evapotranspiration loss
  2. A linear module for estimating throughflow loss from the GWL in the monitoring bore
  3. A static potential profile module for estimating the depth-dependent specific yields from soil texture class
  4. A surface water module to estimate rises in GWL after regional recharge events from historical marsh SWLs.

There are a total of six parameters in the model: canopy type, soil texture class, critical GWL and coefficient for throughflow loss, offset above marsh SWL, and effective ground elevation. A brute-force optimisation program is developed to calibrate the first five parameters.  The effective ground elevation is estimated from local topography.  Predictions of groundwater levels at the 12 near marsh monitoring bores using the calibrated parameters correlate well with observed data.

  1. Rouillard, A., G. Skrzypek, S. Dogramaci, C. Turney, and P. F. Grierson, 2014. Impacts of a changing climate on a century of extreme flood regime of northwest Australia. Hydrol. Eart Syst. sci. Disscuss. 11: 11905-11943.
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