Murray-Darling Basin (MDB) Water Budget Project

MDB was approved as a GEWEX Continental Scale Experiment (CSE) at the 14th Session of the GEWEX SSG in January 2002. The Project aims to enhance the capability of numerical weather prediction models to provide a real-time surface water budget over the Murray-Darling for application by water authorities. The MDB involves both modelling and field studies, and was initiated through collaboration between the Bureau of Meteorology Research Centre (BMRC) and the University of Melbourne’s Department of Civil and Environmental Engineering, under the auspices of the Cooperative Research Centre for Catchment Hydrology. MDB includes contributions from the Commonwealth Scientific and Industrial Research Organization Land and Water, Macquarie University, and the Australian Nuclear Science and Technology Organization.

The Murray-Darling Basin covers a catchment area of 1x10⁶ km² or about 14 percent of Australia. Both the Murray and Darling Rivers have lengths greater than 2,500 km, and so the Basin is one of the world’s major river systems. A key feature of the Basin is that it largely represents a semi-arid zone, and so its ratio of discharge to precipitation is extremely low (less than 0.05) due to the potential evaporation rate being more than twice the precipitation rate.

The Basin is complicated not only by the high evaporation rate, but also by the large interannual variability of the rainfall, mainly due to the impact of the El Nino - Southern Oscillation (ENSO) on the climate of southeastern Australia. This variability in rainfall is amplified in the annual runoff figures, which are more variable than runoff elsewhere in the world (except for parts of Southern Africa that experience a similar climate). The Basin includes the three longest rivers in Australia. The Darling is 2,740 km long from its source in the north to its confluence with the Murray at Wentworth, the Murray is 2,530 km long from its source in the Australian Alps to its mouth on Encounter Bay in South Australia, and the Murrumbidgee is 1,690 km long. There is a range of climatic conditions across the Basin, with cool humid conditions on the eastern uplands supporting areas of rainforest, and sub-tropical conditions in the northeast. The climate to the southeast is temperate, while the large western plains are semi-arid and arid areas. The Murray-Darling Basin is the food bowl of Australia with rich irrigation, farming and grazing land. The Basin accounts for 40 percent of Australia’s agricultural production, utilizing about 70 percent of all water used for agriculture across the nation. The 1,500,000 hectares under irrigation for crops and pastures represents 70 percent of the total area under irrigation in Australia. More than 80 percent of the divertible surface water resource is consumed in the Basin. The Basin holds a population of 2 million people, which is about 10 percent of the national population. The Basin has a naturally saline environment due to its soils and geology. However, human activities have exacerbated these conditions such that high salinity levels in water are causing problems for agricultural, industrial and domestic users.

These objectives are being achieved through a program of combined observation and modeling studies. Core data for the project are collected and managed through the Bureau’s real-time systems, where satellite in situ data are processed through the National Meteorological Operations Centre. The Bureau’s observation program involves the collection of data from both surface-based and space-based instruments. Surface data are obtained from 59 Bureau-staffed stations and from 456 automatic weather stations around the country. The measurement of rainfall is enhanced through an additional 1,690 real-time sites and 3,745 climatological raingauge sites operated by volunteers. Other surface data are obtained from remote-sensing instruments, such as weather watch radars, wind profilers and lightning-detection systems. The MDB project will benefit from other collaborative activities in BMRC. Of special significance is the recent establishment of a USA Department of Energy Atmospheric Radiation Measurement (ARM) site at the BMRC research station in Darwin. Under the ARM project, BMRC will use data from Darwin to improve the parameterization of cloud-radiation interactions in models.

Murray-Darling Basin (MDB) Water Budget Project

MDB Point of Contact