The Murray-Darling is Australia's largest river system. It is also one of the world's major river systems, ranking fifteenth in terms of length and twenty frst in terms of area (Kurian 1989). Table 1 provides some comparisons with other river systems of similar length and catchment area. What immediately stands out is the Murray-Darling's very low mean annual discharge in comparison with the other river systems. Whilst the Murray-Darling is a major river system in terms of its length and catchment area, it is a small one in terms of water discharge or runoff (Figure 1). In fact, of the world's major river systems, its surface runoff is among the smallest.
Figure 1. Major river basins and average yearly discharges of rivers in the MDB. This information is the average of 109 years (1981-2000) of modelled natural conditions discharge. The information comes from the MDBC River Murray Model and the State’s tributary models. (source: MDBC 2005).
|River system||Length, in km||Catchment (km2)+||Mean discharge, in ML/sec|
|Nelson, North America||2,575||1,072,000||2.0|
|Tocantins, South America||2,699||906,000||10.0|
|Tigris-Euphrates, Middle East||2,800||1,114,000||1.0|
* These are river systems with similar features to the Murray-Darling in terms of length, catchment area, and discharge.
+ These figures are rounded. The area used elsewhere in this document for the MDB is 1,061,469km2
Table 1. Some of the world’s major river systems* (source: Encyclopaedia Britannica, Volume 26)
Some definitions on Surface Water Resources
Mean annual runoff
Mean annual outflow
Definitions of terms used
The Murray-Darling Basin is the catchment for the Murray and Darling Rivers and their many tributaries. The Basin extends from north of Roma in Queensland to Goolwa in South Australia and includes three quarters of New South Wales and half of Victoria. Table 2 lists the key indicators of surface water resources for each of the Drainage Divisions (MDBC 2005, NLWRA 2001). Comparing the Murray-Darling Basin with the other Divisions, it ranks third in area, first in terms of developed yield, diversions and water use but third for sustainable yield.
|Drainage Division||Area (km2)||Developed Yield (ML)||Diversion (ML)||Water Use (ML)||Water Allocation (ML)||Sustainable Yield (ML)|
|Gulf of Carpentaria||641,000||58,664||51,559||97,759||69,508||3,824,000|
Table 2. Australia's surface water resources, by Drainage Divisions (source: NLWRA 2001) (To be revised)