- The Murray-Darling is Australia’s largest river system. It is also one of the world’s major river systems, ranking 15th in length and 21st in area.
- The Darling River is the longest river in Australia, measuring 2,740 kilometres from its source to where it meets the Murray River at Wentworth.
- The Darling River and its tributaries rise on the western side of the Great Dividing Range in western Queensland and northern NSW.
- The Darling catchment covers an area of 136,000 square kilometres (about 13% of the Murray-Darling Basin).
- The Darling has a catchment much greater than that of the Murray River but its flow is considerably less in both volume and certainty.
- The upper Darling has a sub-tropical climate with over 250 millimetres of annual rainfall, most falling in the summer period. The lower Darling, where water is distributed, rather than collected, has a temperate climate with a much lower annual rainfall.
- The major tributaries of the Darling River are the Border Rivers in NSW (35% of inflows), Namoi (25%), Condamine (20%), Gwydir (10%), Castlereagh & Macquarie (5%), and Paroo and Warrego (5%).
- All tributaries except the Macquarie are summer-flowing rivers, that is, their flows are derived mainly from summer rainfall
- The Darling River provides about 12 percent of the total annual flow of the Murray River.
- The Paroo and Warrego rivers are highly unpredictable, and usually do not reach the Darling River.
- Unlike the Murray River, the Darling River is known as an ‘unregulated’ river – there are no dams and only a few low-level weirs. However, there are irrigation storages on a number of its tributaries – the Condamine, Border, Gwydir, Namoi and Macquarie rivers.
- Large wetland systems occur along the Darling River and its tributaries, some of which have international significance under the RAMSAR Convention. These include the Macquarie Marshes; the Narran Lakes; wetlands along the lower Gwyder River and the Gingham water course.
- Under the River Murray Waters Agreement of 1915, the flows in the Murray River upstream of Albury and the flows in the Darling River that reach the Menindee Lakes are allocated half each to NSW and Victoria. From the water allocated to them, NSW and Victoria are each required to supply half of South Australia’s water requirement.
- The 2008 MDBC Ecosystem Health Check of the Darling River between shows that the Darling River ecosystem was in poor health (as reported in the MDBC Sustainable Rivers Audit)
- The Sustainable Rivers Audit shows that overall the flow regime of the Darling had fewer high flows and reduced annual volumes. This reflects the diversion of significant volumes of water from the river and the impact of differentially harvesting high flows.
- There is a long history of water quality problems in the Murray-Darling Basin. The summer of 1991-92 saw the largest bloom of blue green algae ever recorded anywhere in the world in the Darling River, which extended over 1,000 kilometres.