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Drought indicators are commonly used tools to describe drought conditions based on key hydrometeorological
variables such as precipitation, temperature, evapotranspiration, soil moisture,
streamflow, and groundwater. Due to the variety of dynamics involved in the propagation of
drought within the hydrological cycle and the implications for impacted sectors, numerous
drought indicators are available in the literature to capture different aspects of the drought
phenomenon (WMO and GWP, 2016). Meteorological drought indices aim at capturing the main
driver of drought represented by precipitation deficits, agricultural drought indices usually focus
on short to medium-term effects of a drought propagating in the hydrological cycle, and
hydrological drought indices focus on medium- to long-term effects recorded on slow-responding
hydrological variables. Often drought research studies focus on a single drought indicator,
selected as the most relevant for the specific application. In this study, we integrated three
drought indicators in order to cover all the above mentioned aspects of drought propagation. In
particular, we adopted indices based on the meteorological forcing (precipitation) and water
balance outputs (soil moisture and streamflow) derived from the Continuum model (see previous
sections for further details).