Catchment Descriptions and Data

2.1 Catchment Description

On Saturday 7 February 2009, the state of Victoria Australia experienced the highest temperature on record with 46.4°C followed by severe bushfires that burnt an area of over 350,000 hectares and caused 173 deaths, which was the second severest among Australia’s worst natural disasters (Biondi & De Luca, 2015; Foster et al., 2011). According to Cai et al. (2009), the 2009 bushfire event was preceded by a positive Indian Ocean Dipole (pIOD) event more so than El Niño events. More specifically, the lower rainfall and higher temperatures produced by pIOD aggravated the dry conditions that finally caused the wide range of bushfire in Victoria. As a result, around 363 km2 of forests in the Melbourne water supply catchments (Feikema et al., 2013) and approximately 24 gauged catchments in Victoria were affected by this severe bushfire event.
<Figure 1 Here Please>
This study selected 14 unregulated catchments that without major water storages or extraction for human use burnt during the 2009 Victorian bushfire. These catchments are located within the southern part of Victoria, Australia (Figure 1). They are small to medium in size, ranging from 84.76 km2 to 629.16 km2. Their mean slope ranges from 14.2% to 32% and their mean elevations range from 273.1 m – 968 m. Soils in these catchments are characterized by deep gradational friable earths or loams as well as some shallow stony earths (Feikema et al., 2013), and they are generally deep with high hydraulic conductivities (Campbell, 1999). The vegetation types in this area are mainly wet sclerophyll Eucalyptus forests known as ash-type eucalypt forest dominated by E. regnans F. Muell. and E. delegatensis R.T (Feikema et al., 2013). More detailed catchment information is summarized in Table 1.
<Table 1 Here Please>
Apart from the preliminary summary of selected burnt catchment attributes, detailed various fire severity proportions of total burnt percentage for burnt catchments were also collected (see Figure 2). Burnt area in majority of catchments are classified as high fire severity such as Crown Burn and Crown Scorch, except some lightly burnt catchments (e.g. Frenchman Ck Jun and Jamieson). Some catchments with relatively low burnt percentage have more severe burns. For example, the Murrindindi above Colwells only has 58.9% burnt percentage, but it is mainly composed of crown burn and crown scorch.
<Figure 2 Here Please>

2.2 Streamflow and meteorological data

The daily streamflow data used in this study were obtained from the Australian Bureau of Meteorology (http://www.bom.gov.au/water/). The climate data including daily precipitation (P), daily incoming solar radiation, daily vapour pressure, daily minimum air temperature, and daily maximum air temperature came from the SILO Data Drill produced by the Queensland Department of Environment and Resource Management (https://legacy.longpaddock.qld.gov.au/silo/). The SILO data has reasonably good quality since its mean absolute error between gridded and gauged data at gauged locations is 1.0°C, 1.4°C, 0.15 kPa and 0.40 mm/day for maximum daily air temperature, minimum daily air temperature, vapour pressure, and precipitation, respectively (Jeffrey et al., 2001). The daily PET was calculated from Morton’s wet environment algorithms (Morton, 1983). Catchment attributes and boundaries were obtained from a dataset generated by Zhang et al. (2013). Apart from the above, this study also used bushfire severity maps obtained from the Victoria Department of Environment, Land, Water & Planning (https://www.data.vic.gov.au/data/) with an estimated accuracy of 95%, which are shown in red in Fig 1.