Bushfires and its implication on water supplies in Victoria, Australia Muhammed A Bhuiyan, Nira Jayasuriya and Michael J Schneider School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne, 3001, Australia Abstract — Australian bushfires have the ability to change the catchment landscape quickly and dramatically. These changes yet can lead to significant changes in both quantity and quality of water yielded. This investigation was conducted to determine the climatic conditions that lead to major bushfires and the response of catchments in Victoria. This was achieved by investigating the Dartmouth, Corryong and Buchan catchments that were burnt out during the 2003 Alpine bushfire. Two main climatic patterns El Nino Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO) play a major role in controlling the weather in eastern Australia. Both negative ENSO and positive IPO tend to exhibit hot drier periods and vice versa. It was found that the bulk of major bushfires occurred during periods of positive IPO and negative ENSO. However the relationship between IPO and ENSO was not strong enough to predict the occurrence of bushfire. Following bushfire the streamflow typically increases due to the reduction in evapotranspiration for 1 to 5 years, followed by a reduction as the forest regrows for 20 to 30 years, then returns to pre fire levels in 120 to 150 years. The magnitude of this reduction though varies widely depending on the type of vegetation, the age of the vegetation and severity of the fire would have profound impact. A recent model was used to predict the changes in streamflow and compared to actual changes that had occurred in the years following the fire. It was found that many measures of water quality like turbidity, nitrogen, phosphorus, suspended solids and nitrate levels have deteriorated significantly. It was found that the probability of exceedance of a critical value for the majority of the measures increased following the fires. Changes in water quality have the ability to make water supplies unfit for household purpose. Water authorities though have certain measures they can undertake measures that can be taken before, during and after the fires.Keywords—component; formatting; style; styling; insert (key words) Keywords – bushfires, Victoria; ENSO; IPO; streamflow; water quality; stormwater. I. INTRODUCTION Landscape altering bushfires are common place on the east coast of Australia. Bushfires are occurring during periods of high daily temperatures, high wind and low relative humidity. The inextricable link between bushfires and climate has been shown by many researchers throughout the years including [1- 3]. While the links between temperature, precipitation and humidity have been proven by all these researchers, this is of limited value if one is unable to predict when these conditions will occur. Recent research therefore has been into what weather phenomena are responsible for producing these conditions. Two climatic phenomena that are thought to increase the risk of fire are the El Nino Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO). These phenomena make the Australian climate warmer and drier than average [4]. References [5-6] stated that during an „El Nino‟ phase the inland eastern side of Australia will have temperatures higher than average with precipitation being lower than average, while a „La Nina‟ phase will consist of temperatures lower than average with precipitation that is higher than average. Reference [7] found a strong relationship existed between the ENSO and the calculated fire risk in Victoria. Similar research by [8] into eight sites across Australia found that at the majority of sites, with the strongest results occurring in south east Australia that a more severe season of fire danger exists, with twice as many days with high fire danger occurring, when the Southern Oscillation Index (SOI) is negative compared to when it is positive. This conclusion that a negative SOI leads to increased fire danger now appears to be the general consensus. Reference [9] explains that when the IPO is in positive range temperatures warmer than average can be expected and vice versa in Australia. The IPO has also been found to be related to the ENSO. Reference [9] states that the IPO modulates inter-annual ENSO related climate variability over Australia due to strong link between ENSO and positive IPO events. Reference [10] similarly found that during positive IPO events the occurrence of intense El Nino events is more regular which as discussed have a high correlation with producing drought conditions leading to worse bushfire conditions. Therefore many researchers believe that a positive IPO event matched with an El Nino or positive Southern Oscillation can be an indicator that a serious risk of bushfire could occur during the summer season ahead. Reference [4] investigated this theory and found that most of the serious bushfires that have occurred in Canberra over the last century correspond with a positive IPO and positive SOI. As can be seen above there appears to be a strong connection between the climate and certain climate phenomena and the bushfire risk and the actual occurrence of bushfires. This study will focus on the occurrence of bushfires in Vitoria and determine if there is a correlation with IPO and ENSO. If a correlation did exist this would allow authorities to introduce measures in seasons that are expected to be of high bushfire threat to protect important water resources or attempt to minimize the impacts that could result from bushfires occurring in catchments. Scientific Cooperations Journal of Civil Engineering and Architecture, Vol. 2, Issue 1, Feb. 2016 1