Lack of snow in the Italian Alps leads to drought in northern Italy

Dhe researchers at the Earth Observation Center (EOC) of the German Center for Aeronautics and Astronautics (DLR) analyzed approximately 15,000 satellite images of the Alps over a 37-year period to determine that last spring the snow line, thenival floor, in the Italian Alps was at an average altitude of 400 meters, even, in some regions, almost a kilometer higher than usual. Scientists also studied the effect of snow cover in the Alps on water scarcity in northern Italy. This year Northern Italy has experienced one of the worst droughts in 70 years.

Header image: variation of snow limits in Valle d’Aosta (northern Italy) . (DLR)

The researchers analyzed the position of the snow line in nine regions of the Italian Alps, including the Aosta Valley and the South Tyrol. Important tributaries of the largest river in Italy, the Po, arise there. Especially in spring, rivers like the Dora Baltea or theadige are largely fed by meltwater. When there is no snow, Italy’s most populated region faces water shortages.

According to Jonas Kohler, who conducted the study at the EOC:

The snow line indicates the height at which the mountains are covered with snow. The higher this limit, the less snow, and therefore potential meltwater, is available. For example, in Ticino, the border region between Italy and Switzerland, the snow line in March this year was 625 meters above the long-term average. This means that the region’s snow cover was 56% lower than normal.

The research team obtained these results from images acquired by the Earth observation satellite Landsat. The dataset contains monthly snowline observations for the entire Alpine region since 1985. Landsat has a spatial resolution of 30 meters. This allows snow mapping even in the complex terrain of high mountain regions. As the Landsat archives cover a long period, it is possible to create chronological sequences.

Still according to Jonas Kohler:

The drought in northern Italy was set against a combination of high temperatures and low rainfall over the winter and spring of 2022, followed by several heat waves. Satellite images clearly show the effects of these weather conditions on snow cover. Italian authorities have restricted water use in regions such as Lombardy and Piedmont – affecting irrigated agriculture in the Po Valley.

The consequences of a winter with little precipitation were also felt in Germany: the Rhine, for example, was partly no longer navigable due to low water levels.

For Jonas Kohler:

Satellite data shows that the snow line in large parts of the Alps is moving upwards by several meters per year. Continuous observation of the snow line will make it possible to identify possible droughts very early on.

Presented on the website of the German Center for Aeronautics and Astronautics: Satellitenbilder zeigen Schneemangel in den italianischen Alpen.