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Integration of Groundwater Models within an Economical Decision Support System Framework
MDSIM 05 (2005)
  • Amgad ELMAHDI
  • Redha Beddek
  • Bret Barnett
  • Tanya Kennedy

EXTENDED ABSTRACT Groundwater is a vital resource in Australian agriculture. Increased demand for water resulting from rapid economic development accompanied by poor climatic conditions (e.g. low rainfall levels) has induced an increased reliance on groundwater harvesting to sustain intensive irrigation practices. Overdraft of groundwater as a result of reduced surface water availability, increased economic viability of farms and the capping of river catchment allocations have considerably lowered water tables. This paper describes a decision support system to aid in the sustainable water resource use in the Werribee Irrigation District (WID) in Victoria. This particular district provides an ideal set up for the investigative work described below as it has a fully calibrated groundwater model and more importantly, it is at risk of salinization due to sea water intrusion. A decision support system linking crop water requirements with the available water for irrigation (surface and groundwater) is developed using a systems dynamic approach (system dynamics offers a new way of modelling the future dynamics of complex systems) by dynamically linking crop distribution patterns with the behaviour of a coastal aquifer using a finite difference three dimensional modelling approach. This allows the optimisation of agricultural production while respecting sustainable groundwater levels in the aquifer. The Modflow 2000 code is used to simulate groundwater dynamics in the Werribee Irrigation District. VENSIM-DSS software, a system dynamics tool, was used to optimise crop distribution in the Werribee Irrigation District (WID) in Victoria. This was done by linking Crop distribution mix and water demand under set constraints to groundwater drawdown spatial distribution resulting from Modflow simulations scenarios. The study time frame was set to 12 months. Four case scenarios were tested: a high water use scenario, a medium water use scenario, a no rice water use scenario and a low water use scenario (Vegetables Only). It was found that the “Vegetable Only” scenario was the most sustainable as pumping didn’t breach the predefined sustainability limit1. Economic Surface and Groundwater Model (ESGM) was linked to a calibrated numerical Model developed under Modflow (USGS, 1984). The dynamic link takes care of the constraint checking and makes it easier for non-modellers to test various scenarios. This management tool as proposed presents the advantage of linking system dynamics to physical processes hence giving more realistic outcomes

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Amgad ELMAHDI, Redha Beddek, Bret Barnett and Tanya Kennedy. "Integration of Groundwater Models within an Economical Decision Support System Framework" MDSIM 05 (2005)
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