The influence of climate science on water management in Western Australia - Lessons for climate scientists

Water flow into dams that supply Perth in Western Australia (WA) has fallen by 50% since the mid-1970s, and this has severely tested water managers. Climate change scenarios available since the 1980s have suggested that global warming will reduce rainfall over southern Australia, including Perth. Water managers recognize the uncertainties associated with the projections, including the significant differences that exist between the timing and magnitude of the observed changes and modeled projections. The information has, nevertheless, influenced their decision making. To understand why, we need to consider the broader environment in which the water managers operate. One key factor is that the imposition of severe water restrictions can lead to significant economic loss and increased unemployment. Prolonged restrictions can therefore create strong debate in the wider community. In recognition of this, state government policy requires that water managers ensure that the chance of having severe restrictions is kept low. Severe restrictions have not been imposed since 1979, but moderate restrictions are more common, and were imposed as recently as 2002. Scrutiny of water management can become intense even after moderate restrictions are imposed, and at these times it is unacceptable to many people if a known risk-even if very uncertain-is perceived to have been ignored in earlier planning. Climate science has established regional drying driven by global warming as a risk, and so global warming has to be addressed in planning. Water managers also need climate science to reassure the public that the restrictions imposed were necessary because of unprecedented changes in rainfall, not because of poor management. In recent years much of the influence that climate science has had on water managers can be attributed to the Indian Ocean Climate Initiative (IOCI). IOCI is a research partnership between the Western Australia Water Corporation, other state government agencies, and two national meteorological research organizations. Water managers saw their participation in IOCI as one strand of a broader risk management plan. They did not have the luxury of deferring important decision making for certainty that climate science might never bring, but were very interested in what climate science might provide "now." The participation of water managers in IOCI enabled them to influence research planning to better meet their needs. Water managers did not just want predictions or technical explanations of an individual scientist's latest work. They wanted reliable and balanced advice on broader issues, explanations, clarification, realistic expectations, and an appreciation of uncertainty. They wanted climate information related to water management issues in a form relevant to the region. "Localized" information is more suitable for inclusion in their decision making, and of more use to them for both informing, and stimulating discussion within, the wider community.