Detecting and attributing drought-induced changes in catchment
hydrological behaviors using a data assimilation method
Yanghe Liu a, b, c, Pan Liu a, b, c,
Lu Zhang d, Xiaojing Zhang a, b, c,
Yunfan Zhang a, b, c, and Lei Chenga, b, c, *
a State Key Laboratory of Water Resources and
Hydropower Engineering Science, Wuhan University, Wuhan 430072, China
b Hubei Provincial Collaborative Innovation Center for
Water Resources Security, Wuhan 430072, China
c Hubei Provincial Key Lab of Water System Science for
Sponge City Construction, Wuhan University, Wuhan, Hubei, China
d CSIRO Land and Water, Black Mountain, Canberra, ACT
2601, Australia
* Correspondence to: Dr. Lei Chenglei.cheng@whu.edu.cn
Abstract: It is widely
recognized that multi-year drought can induce changes in catchment
hydrological behaviors. However, at present, our understanding about
multi-year, drought-induced changes in catchment hydrological behaviors
and its driving factors at the process level is still very limited. This
study proposed a new approach using a data assimilation technique with a
process-based hydrological model to detect multi-year drought-induced
changes in catchment hydrological behaviors and to identify driving
factors for the changes in an unimpaired Australian catchment (Wee
Jasper) which experienced prolonged drought from 1997 to 2009. Modelling
experiments demonstrated that the multi-year drought caused a
significant change in the catchment rainfall-runoff relationship,
indicated by significant step changes in the estimated time-variant
hydrological parameters SC (indicating catchment active water storage
capacity) and C (reflecting catchment evapotranspiration dynamics),
whose average values increased 23.4% and 10.2%, respectively, due to
drought. The change in the rainfall-runoff relationship identified by
the data assimilation method is consistent with that arrived at by a
statistical examination. The proposed method provides insights about the
drivers of the changes in the rainfall-runoff relationship at the
processes level. Declining groundwater and deep soil moisture depleted
by persistent evapotranspiration of deep-rooted woody vegetation during
drought are the main driving factors for the catchment behaviors change
in the Wee Jasper catchment. The new method proposed in this study was
found to be an effective technique for detecting both the change of
hydrological behaviors induced by prolonged drought and its driving
factors at the process level.
Keywords: multi-year drought; rainfall-runoff; nonstationary;
data assimilation; Particle filter; Australia Millennium drought