INTRODUCTION The Murray-Darling Basin, which covers an area of 1.06 million square kilometres, equivalent to one-third of the total area of Australia, plays a very important role to the country. Not only does it provide one-third of Australia's total income, over two million people depend on its resources for their livelihood (Burton 1991). Unfortunately, the Basin has been suffering from serious problems created by those people who are living on it. Unsustainable management practices since the moment of European settlement have destroyed the Basin's land and water resources so severely that the destruction has been called "the crisis of land and water management'. Land degradation, water quality and land and water salinity are three major problems considered by the Murray-Darling Basin Commission as the consequences of negative management practices. In this paper, I will examine three major issues of land and water management, which are land clearing, unsustainable agricultural practices and irresponsible irrigation. Some suggested solutions to the problems, which I think are the most appropriate, will also be presented.
MAJOR ISSUES OF RESOURCE MANAGEMENT IN THE MURRAY-DARLING BASIN Land clearing The first serious issue of resource management is land clearing or clearing of native vegetation. This is considered a major issue in the Murray-Darling Basin as it leads to many significant problems such as land and water degradation. As Crabb (1997, p. 70) states in his study, since the moment of settling, Europeans have made a great impact on vegetation in the Murray-Darling Basin. Many species of deep-rooted native vegetation have been cleared and replaced by shallow-rooted crops and pastures (Alexandra & Eyre 1993). Indeed, a recent study has estimated that about 14.4 billion trees in the area have been lost over two centuries of European settlement (Walker et al. 1993).
There are some serious problems related to land clearing. The first major effect of land clearing is land salinity, especially in dryland regions. Over time, much evidence has shown that land clearing has been the main cause to dryland salinity (Walker et al. 1993, Hatton et al. 1993). Clearing of deep-rooted trees has resulted in a rise of water tables and waterlogging. Since ground waters are usually saline, salt from water tables will be brought to the surface and causes salinity. In addition, when there is less deep-rooted vegetation, water will more easily evaporate to the atmosphere and leave salt behind in the soil and ground water which also makes the soil and ground water more saline (Scott, P. 2000, pers. comm., 16 March).
The second major effect of land clearing is soil erosion. Indeed, the clearing of native vegetation has led to both forms of soil erosion, i.e. wind erosion and water-induced erosion. Johnston (1993), in his study, emphasises that there is a direct link between land clearing and wind and water erosion and he even regards unrestrained land clearing as "a disaster of catastrophic proportions'. Supporting the statement of Johnston, Crabb (1997, p. 125) states that when the soil does not have plant cover protection, it would be in danger of wind erosion. A similar situation happens to water-induced erosion. Indeed, it is discussed that when the soil is left bare and prone, heavy rainfalls will likely cause erosion (Crabb 1997, p. 126).
In addition to those two most serious problems, land clearing also causes some other important problems such as water turbidity as it results in land and streambank erosion, which are the main causes of turbidity (Crabb 1997, p. 138).
Although land clearing is not the only cause of those problems discussed...