Oral Presentation Australasian Groundwater Conference 2017

A technique for estimating optimal constant extraction rates for water levels to remain above pre-specified minimums in the model domain (#208)

Kiran Bajracharya 1
  1. Department of Science, Information Technology and Innovation, Dutton Park, QUEENSLAND, Australia

The Resource Operation Plan (ROP) process in Queensland seeks to convert water licences into volumetric allocations. The announced entitlement reflects the volume of water available based on measured groundwater levels. When groundwater levels are low, the announced entitlement would also be low.

The main objective of this paper is to show the use of a technique to estimate the optimal conservative entitlement such that pre-selected minimum water levels are maintained during the simulation period. By using different minimum water levels, the storage behaviour of the system can be established for the ROP.

The calibrated Central Lockyer Groundwater model was used to test this method. The model covers the simulation period from 01/07/1987 until 30/06/2014. It has a single convertible layer with variable transmissivity and simulates groundwater levels using extractions and recharge as the major inputs with the time-variant specified fixed head as the boundary in the upper and lower reaches.

This model was used to set up the scenario model for which the optimal constant extractions from 24 management zones were to be determined. The penalty function method was used to determine the conservative optimal extraction rates such that water levels never went below the specified minimums. The historical minimum water levels of September 1995 were used as the target water levels.

The technique for estimating optimal extractions using the penalty function method was successfully implemented. The results of storage behaviour for the scenarios with different minimum water levels were compared to the storage behaviour of the calibrated model. The analyses of these storage behaviours and conservative extraction rates are helpful in understanding the simulated behaviour of the system. From this, rules for announced entitlements can be developed.

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