Declining rainfall and renewable water resources

The trend is negative. That is, total precipitation is falling and so is the so-called renewable water resource. A trend that, as shown by the assessments produced by Ispra through the Bigbang model, is constant over the period from the 1950s to 2025.

A 9% decrease by 2025

In 2025, in fact, total precipitation in Italia amounted to 963.4 millimetres, equal to about 291 billion cubic metres, a decrease of about 9% compared to 2024, a year considered by experts to be 'particularly rainy'. "However, 2025 marks a slight increase of 2% compared to the average annual precipitation of the 1991-2020 period, the last 30-year climatological period, which amounted to about 285 billion cubic metres," the Ispra report points out. In 2025 the renewable water resource, i.e., the amount of precipitation net of evapotranspiration loss, estimated at about 128 billion cubic metres, was down compared to historical averages, more than 7% less than the long-term annual average of about 138 billion cubic metres, 4% less than the average of the last thirty-year climatological period, and about 19% less than in 2024". And that's not all: "The current update of the hydrological balance," the Higher Institute for Environmental Protection goes on to say, "therefore continues to confirm the negative trend observed from 1951 to the present, referring in particular to the availability of renewable water resources at a national level.

The presentation on 24 March

The study carried out by the researchers analysed trends and deviations from the average values of the long period 1951-2025 and the 30-year climatological period 1991-2020. The details of the assessments will be presented on 24 March during the Workshop "Hydrological balance and water resource availability: 2025 update, seasonal forecasts and climate projections", organised by Ispra on the occasion of World Water Day.