Gnangara Decision Support System: Stochastic climatic- social-economic analysis for sustainable groundwater management

Amgad ELMAHDI, CSIRO LAND AND WATER
Don McFarlane

Abstract

The combination of global warming, low rainfall, reduced recharge/run off and increasing water extraction/demand has resulted in (falling groundwater levels ) a situation that is no longer ecologically or socio-economically sustainable fresh water system. Simply in Gnangara mound groundwater system, more water is leaving the system to meet consumptive demand than is coming into the system through rainfall/recharge. This situation resulted in decline water table/level significantly in some parts of the mound. This impact observed as dieing vegetation, drying wetlands and caves and reduced sustainability of the system into future. Water authorities are now facing a great challenge to meet requirements with new urbanization plan, reallocating horticultural area, increasing population and increasing demand. This paper provides a better understanding of how the groundwater system on Gnangara mound responds to the change in the climate and landuse with evaluation of its socio-economic impacts and tradeoffs. In order to evaluate this system, an object-oriented system dynamics approach has been used to develop an integrated model. Preliminary results from the development and application of the model for quantifying sustainability of Gnangara mound system is presented with emphasis on the understanding of the tradeoffs of changing climatic conditions and landuse planning. Water levels vary significantly under different climatic conditions (recharge regimes). Changing and reallocating landuse is able to improve recharge in some parts of the system but this cannot reverse the overall trend of falling levels as the climate signal is pervasive.