Introduction
Hydrologic systems are dynamically influenced by both anthropogenic
activities and natural variability (Pathiraja et al., 2016). Among them,
bushfire is an important cause of hydrological change in fire-prone
landscapes (Shakesby & Doerr, 2006). Bushfire can result in vegetation
loss and post-fire microenvironment temperature rise, which can change
hydrological processes such as interception, evapotranspiration and soil
water storage. Effects of bushfire on streamflow can be estimated using
the paired catchments method (Liu et al., 2004). Many studies have been
conducted to understand the hydrological change due to vegetation cover
changes using the paired catchment method (Brown et al., 2005; Loon et
al., 2019; Zégre et al., 2010). However, the paired catchment analysis
has drawbacks since it only involves small catchments and is expensive
to conduct (Zhang et al., 2011). An alternative method is to use the
time-trend analysis which does not require control catchments and can be
applied to small to large catchments.
Apart from anthropogenic activities, climate variability can
significantly affect streamflow and should be considered when evaluating
the streamflow response to vegetation change due to bushfire (Lane et
al., 2005; Zhang et al., 2011). Several methods have been developed and
applied to separate the effects of vegetation change and climate
variablity (Tuteja et al., 2007; Zhang et al., 2008; Zhao et al., 2012).
These methods firstly identify key factors affecting streamflow and
estimate the total streamflow changes using observed data. The second
step is to determine the changes in streamflow due to the key factors
such as vegetation change caused by bushfire and then to attribute the
remaining changes to other factors such as climate variability. These
methods can provide consistent estimates of vegetation change and
climate variability impacts on streamflow in the catchments being
considered (Zhao et al. (2010)).
Many attempts have been made to quantify the impacts of bushfire on
hydrology in the past five decades (Anderson et al., 1976; Brown, 1972;
Daniell & Kulik, 1987; Neary et al., 1999; Robichaud et al., 2000;
Tiedemann et al., 1979). Some recent studies mainly focused on
hydrological modeling in bushfire impacted catchments, aiming to better
estimate the streamflow variation under bushfire impacts (Folton et al.,
2015; Heath et al., 2014; Mannik et al., 2013; Papathanasiou et al.,
2015; Seibert et al., 2010; Zhou et al., 2015). To date, most of these
studies mainly investigated or evaluated the bushfire impacts on
streamflow but few of them quantified the impact of climate variability.
This study aims to quantify the climate variability and bushfire impacts
on streamflow for 14 catchments located in Victoria, Australia that have
been severely burnt by the 2009 Victoria bushfire, the second severest
national bushfire disaster. The specific objectives are: i)
investigating annual streamflow trends from the 14 catchments; and ii)
separately estimating the vegetation change caused by bushfire and
climate variability impacts on streamflow using time-trend analysis and
statistic sensitivity-based model