Multiyear drought assessment for long term rainfall and river flows in Italy

Long term time series of daily rainfall and daily river flows are analysed in order to detect the occurrence of drought rich periods through the application of the theory of runs. In detail, we consider the time series of the daily rainfall in Bologna (1813-2019) and daily river flows of the Po River at the closure section (1920-2017). These data sets are a valuable opportunity to assess long term changes of precipitation and water resources availability and the effect of recent climate change. The occurrence of multiyear droughts is a major concern in the context of Italy for the potential impact on irrigation as well as water supply for civil and industrial use. The design suitable adaptation techniques needs to be based on a careful assessment of the probability of multiyear droughts and their intensity. Our results point out the occurrence of critical events along the whole span of the considered observation period, as well as the contingency of a number of recent droughts that point out a condition of potential vulnerability.