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Abstract:
A comprehensive insight to the drought propagation process and its driving mechanisms is of great significance to drought resistance building and water resources management. Using observational data as well as model simulated data, the non-linear relationship between meteorological and hydrological drought is quantified in terms of probability, propagation time and development/recovery features. The propagation from meteorological to hydrological drought may falls in one of three categories, i.e., (1) Type-1, one or several meteorological droughts trigger a hydrological drought, (2) Type-2, a meteorological drought occurs but no hydrological drought follows, and (3) Type-3, a hydrological drought occurs without a proceeding meteorological drought, which is caused mostly by human activities. Type-1 propagation typically has the features of lengthening of duration, amplification of severity, lag of onset time, and reduction of speed. Drought propagation is controlled by both endogenous factors (underlying surface and human activities) and exogenous factors (climate). Climate factors have significant effects on hydrological drought duration, while catchment properties (especially the topographic index) significantly affect hydrological drought severity and propagation characteristics. Precipitation-streamflow relationship changes significantly during extreme drought, resulting in lower runoff coefficient. Exogenous mechanism represented by precipitation and endogenous mechanism represented by baseflow control the shift of precipitation-streamflow relationship during drought propagation. Reservoirs have significant effects on alleviating the duration and severity of extreme droughts, but little effects on the average duration and severity of hydrological droughts. Land use change has little impacts on drought propagation at the catchment scale.
