The hydrological situations expected to be of most concern in the region are the water-limited drought-prone areas, the exposure of the built environment to possible increases in flooding, the supply of potable water to remote indigenous populations in inland Australia and on low-lying islands, and the progressive loss of snowfields.
Integrated catchment management provides an adaptation framework for the long-term management of catchment water and surface properties and the short-term tradeoffs between competing demands for water. Already, major systems such as Australia's Murray-Darling River system are subject to intensive management, but generally this does not include consideration of possible decadal-scale changes or even of the predictable El Ni�o-related seasonal-to-annual variations. Water pricing and water efficiency initiatives may be used as an effective adaptation strategy (Fenwick, 1995; McClintock, 1997). The risk of landslides and soil erosion can be reduced through informed land management, particularly by avoiding vegetation clearance in vulnerable areas and by rehabilitating exposed areas that have been cleared.
Urban planning and management will be needed to deal with increased flooding risk-for example through provision of retention basins and zoning. Any slow change in mean rainfall or rainfall intensity, if well-enough known in advance, could be accommodated within the lead time of about 10 years needed for planning and constructing major facilities. Dams and flood-protection works can be redesigned and rebuilt and vulnerable buildings relocated, albeit at considerable cost. However, any slow increase in interannual rainfall variability may result in early stresses for supply systems designed to cope with existing rainfall variability; at such times, the adaptation options would be very limited, as was shown during the public water supply crisis in Auckland in 1994. Measures needed to improve the water supply situation of indigenous peoples in inland Australia and on Australia's low-lying coastal islands are discussed in Moss (1994).
Adaptations to change in snowfields and glaciers are very limited. Artificial snowmaking is a potential strategy for skifield operators, but only to a limited extent because of the strong impact of temperature increases on snow amount, the environmental impacts of the large water storage dams required, and the costs involved.
Although many management and engineering adaptation options exist, the magnitude of the financial exposure and the considerable time and expense involved in adaptations indicate a high vulnerability with respect to hydrology.
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