The Murray–Darling Basin is defined by its water. The geography of the Basin takes in 23 rivers and their catchments. Almost 4 million people, inside and outside the Basin, need its water for the survival of their families, communities and industries. A vast array of animal and plant species, and the environments in which they live, have evolved and adapted to the seasonal patterns of water flow through the Basin’s rivers.
There is so much life and prosperity dependent on the water of the Basin that it is quite extraordinary that less than 15% of the area of the Basin contributes to runoff in the river systems — except in times of flood.
Most of the water in the Basin comes from the southern and western sides of the Great Dividing Range, flowing into the 23 major rivers, including Australia’s 3 longest, the Murray, Murrumbidgee and Darling. High evaporation rates, expansive floodplains and significant water diversions for towns and agriculture mean that much of the surface water in the Basin does not reach the ocean.
Groundwater is also an important water source for Basin communities and industry. Groundwater is water contained in soil or rock below the ground surface. It comes from surface water that flows downwards through sediment or rock, forming an aquifer. In turn, the aquifer may reconnect with the soil surface, or with rivers and streams somewhere else in the landscape.
The water of the Basin’s rivers and the aquifers beneath its plains quickly attracted European settlers, and the Basin’s land and water resources were put to work. Dams were built to capture water in the upper catchments, and river flow was regulated to ensure water supply met water demand — which was often contrary to natural flow patterns.
Basin residents and governments have long recognised the need to share the resources of the Basin equitably and sustainably. For over 100 years, there have been agreements, policies and plans addressing the use and management of the waters of the Basin. In the 21st century the pressures on the river system are significant. Population growth, thriving agricultural industries and ongoing cycles of drought and flood must be balanced with the need to carefully manage the natural environment — which underpins the traditional culture, modern social fabric and economy of the Basin.