|Book Title:||WATER RESOURCES MANAGEMENT V|
|Author:||Elmahdi, A. ; McFarlane, D.|
|Book Group Author:||NA|
The Gnangara Sustainability Strategy is a cross-government initiative that aims to ensure there is sufficient groundwater in the Gnangara Mound for drinking and commercial use, and to meet existing and future environmental needs. The Gnangara Groundwater System (GGS) is a large aquifer situated in the southwest region of Western Australia. Historically, the GGS has been considered to be an infinite reservoir for water, but this impression has quickly shifted following the realization that 45 GL of water has been lost per annum since the late 1990s. The main causes for this loss are lower rainfall since 1975; land uses that reduce recharge; and increased water extraction. As a result, many significant environmental features, especially wetlands, are declining in health and value. The GGS faces increasing demands for its water from several key users within the public water supply, environmental and agricultural sectors. However, declining water levels related to climate change, demand urgent prioritisation of a set of inter-sectoral and inter-temporal land use planning and water abstraction rules that would maximize societal welfare while ensuring the sustainability of this crucial water source and its dependant ecosystems. The sustainable management of the GGS is a major problem for water and environmental managers because of the complexity and interconnectedness of the system. Innovative modelling approaches should be employed to assist in better decision making by modelling the feedback loops inherent in the system and analysing the impact of alternative land use and water policy scenarios. This paper details a systems approach to developing an integrated decision support system (DSS) to enable these complex land and water use options to be evaluated in economic, social and environmental dimensions. A total of 29 sub-areas were identified (based on flow direction, allocation and similar land-use) and modelled under six geographical zones. Each sub-area was modelled by the main interconnected six modules and quantitative indicators (environment, economic and social) values were calculated. Seven scenarios were tested: i) business as usual (BAU); ii) maximizing recharge; iii) maximizing biodiversity; iv) maximizing short term economic gains; v) a Mixed use Post-Pine; vi) maximizing food security, and; vii) zero abstraction for public water supply by 2013. Preliminary results from the DSS are presented with an emphasis on understanding the tradeoffs between these scenarios. Most scenarios lead to a declining water table in the GGS, which by 2030 is up to 8 meters lower from the current levels. This would lead to a significant loss of biodiversity and wetlands. Changing and reallocating land use (e.g. grassland as post pine land-use) could improve recharge but this cannot reverse the overall trend of falling levels because climate change is pervasive.
|Organization:||Wessex Inst Technol; WIT Transact Ecol & Environm|
DSS; groundwater; sustainable management; scenario analysis; integrated modelling
|Source:||Web of Science|