South Australia is currently leading the rest of the Murray Darling Basin (MDB) governments in advocating for a return of at least1500 gigalitres of water per year to the Murray by 2018. However, a review of the scientific literature suggests that the river needs about double this to have any chance of returning to health.
Australia s leading river ecologists state that annual flow returns of 1500 gigalitres, will give the river a moderate chance of regaining its health (1). In other words, this is the bare minimum that must be returned.
It is predicted that more than 2000 gigalitres may be lost from the system over the next 20 years due to:
The Murray Darling Basin Commission is making similar predictions, suggesting that by 2023, over 2000 gigalitres of system inflows will be lost as a result of climate change, reafforestation, growth in groundwater use and the construction of farm dams. Climate change alone is predicted to reduce system inflows by at least 1100 gigalitres annually(3), which is about 1.5 times the amount South Australia currently extracts from the river.
A study completed by CSIRO Land and Water suggests that the total Water Requirement of irrigated agricultural land uses in the MDB in 1996/97 was 9,346 gigalitres and which increased by nearly 29% to 12,050 gigalitres in 2000/01(4). This alarming increase, despite the presence of a cap, is attributed in part to water use efficiency savings being used to increase irrigation rather than river flow and increased groundwater extraction.
The point that is being emphasized is that water losses of more than 1500 gigalitres from the MDB are a possibility by 2018. Therefore, assuming 1500 gigalitres have been successfully returned over the proposed 15 year period, the rivers health will be more critical than it is today. To achieve 1500 gigalitres of increased flows by 2018, flow increases of approximately 3000 gigalitres may have to be acquired.
Recently, a report documenting the rapid decline of River Red Gums in the Lower River Murray was released. It states that tree decline has increased substantially between 2002 and 2004 from 51.4% of all trees counted in 2002 to 75.4% of all trees counted in 2004 (5). This rate of decline could lead to the deaths of all Red Gums along the river within the next few years. The ecosystem services (mitigation of salt and erosion, provision of habitat etc..) that the red gum provide, may well be worth more that the cost of buying water entitlements.
MDB governments could purchase water entitlements, place them into an environmental water bank and reduce the current consumptive pool accordingly. We believe this should happen as a matter of urgency, addressing over allocation and bringing irrigation and river health into a sustainable relationship.
(1) Cooperative Research Centre for Freshwater Ecology (2003) Ecological Assessment of Environmental Flow Reference Points for the River Murray System Interim Report prepared by the Scientific Reference Panel for the Murray Darling Basin Commission, Living Murray Initiative.
(2) Young & McColl, 2003, Robust Reform: The Case for a New Water Entitlement System for Australia, The Australian Economic Review, vol. 36, no. 2, pg. 227.
(3) Murray Darling Basin Commission, 2003, Prospects for future deterioration in flow in the Murray Darling Basin .
(4) Bryan & Marvanek, 2004, Quantifying and valuing land use change for Integrated Catchment Management evaluation in the Murray-Darling Basin 1996/97 2000/01, pg.5.
(5) Brett Lane & Associates Pty Ltd, 2004. Survey of River Red Gum and Black Box Health along the River Murray in New South Wales , Victoria and South Australia .
