06 Nov 2023
 | 06 Nov 2023
Status: this preprint is currently under review for the journal HESS.

60-years analysis of drought in the western Po River basin

Emanuele Mombrini, Stefania Tamea, Alberto Viglione, and Roberto Revelli

Abstract. Since the start of the 21st century, greater focus has been put on drought and its wide range of environmental and socioeconomic effects, particularly in the context of climate change. This is especially true for the North-western region of Italy, comprising the Piedmont and Aosta valley, which have been affected in recent years by droughts that have had acute effects on water resources and water security in all sectors, including agriculture, energy and domestic use. The region also belongs to the Mediterranean hot-spot, characterized by faster than global average warming rates and higher vulnerability to their effects. Therefore, characterizing the observed changes and trends in drought conditions is of particular significance. To this end, 60 years of precipitation and temperature data from the North West Italy Optimum Interpolation data set are used to calculate the drought indices SPI (Standardized Precipitation Index) and SPEI (Standardized Precipitation Evapotranspiration Index) at a shorter (3-month) and at a longer (12-month) time scale. First, trend analysis on precipitation and temperature is performed, finding limited areas with significant precipitation decrease and, conversely, a general temperature increase over the region, with higher values found in the higher elevation areas. Changes in meteorological drought are then evaluated, both in terms of drought indices trends and in terms of changes in the characteristics of drought periods, on both a local and regional scale. A relation between the altitude of the area and the observed changes is highlighted, with significant differences between the plain and mountainous portion of the region. The differences are mainly related to the observed trends, with the low-altitude part of the region displaying a tendency towards dryer conditions not in common with the mountainous area. Significantly, no trend is found at a region-wide level but is instead found when considering homogeneous areas defined by terrain ruggedness. Furthermore, changes in the number of drought episodes and in their severity, duration and intensity are found to be correlated with terrain ruggedness at all time scales.

Emanuele Mombrini et al.

Status: open (until 01 Jan 2024)

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Emanuele Mombrini et al.

Emanuele Mombrini et al.


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Short summary
In north-western Italy overall drought conditions appear to have worsened over the last 60 years, due to both precipitation deficits and increased evapotranspiration caused by temperature increase. In addition to changes in drought conditions, changes in the characteristics of drought periods, both at a local and at a region-wide level, are found. Links between all the aforementioned changes and the terrain topography are highlited, finding generally worse conditions in lower lying areas.