222893e

TRANSBOUNDARY WATER MANAGEMENTThe Murray–Darling Basin Plan: cooperationin transboundary water managementKerryn Molloy, Senior Science Writer, Murray–Darling Basin AuthorityLate last year, Australia brought into law its first whole-ofbasinplan (the Basin Plan, 2012) for our most importantwater resource: the Murray–Darling Basin. This plansets limits on the quantities of water extraction for human(consumptive) use.Reaching this agreed limit for sustainable use of the basin’s waterresource is a world first for transboundary water management. Thebasin extends across borders and has important social and culturalvalues in addition to its national economic importance. Achieving widescalereform depended on agreed goals, overall stakeholder acceptanceand extensive cooperation between all levels of government.Map of the Murray–Darling Basin, showing contextwithin state boundariesSource: MDBAAbout the Murray–Darling BasinSpanning parts of four states and all of the AustralianCapital Territory, the basin contains Australia’s largestriver system, comprising the Murray and Darling riversand their tributaries. Ranked fifteenth in the world interms of length (3,780 km) and twentieth for area, thebasin extends across 14 per cent of Australia’s land mass(approximately equal to the area of France and Spaincombined). However, in the driest inhabited continenton Earth and with very low topography, these long, slowflowingrivers have high evaporation rates (around 94per cent of rainfall). The Murray–Darling system thereforecarries one of the world’s smallest volumes of waterfor its size. It is home to 2 million people (including 42Aboriginal nations) and directly supports another million.The basin’s approximately 60,000 agricultural businessesproduce around 40 per cent of Australia’s foodand fibre (estimated to be worth $A13 billion annually).Around a third of this is irrigation-assisted; andirrigation is the largest consumer of water in the basin.Important for tourism and recreation, about 30 percent of the basin’s land cover is native forest; and itcontains about 60,000 km 2 of floodplain and 30,000wetlands. Many of these are of national importance,and 16 are listed under the Ramsar Convention onWetlands of International Importance. There are at least95 threatened species dependent on basin ecosystems.Water resource development and managementSince the mid 1800s, water resource development hasgrown from initial pumping stations along the RiverMurray to support settlers and livestock, to the presentwhere we have more than 3,000 water regulation structures.The combined capacity of the major storages is about34,500 Gigalitres (GL). As a long-term average, 42 per centof the total surface water run-off to the Murray–DarlingBasin is diverted for consumption. In the connected riversystems, water is traded across and between catchments.In Australia’s climate, supporting the economicbase without overly compromising water-dependantecosystems is challenging. The Murray–DarlingBasin receives little direct rainfall and suffers periodicdrought - and droughts can last a decade. Inthe southern system, most rain falls across the upperreaches of the rivers in New South Wales and Victoria,and extraction by these states (particularly during[ 77 ]