At the end of this month the hydrological year comes to an end in Switzerland – it always lasts from October 1 to September 30 of the following year. In the majority of the country there is no more precipitation until then, in the north and east the amounts are hardly worth mentioning. Therefore here already a rough review.
The true annual balance of precipitation
Other names for the hydrological year would also be runoff year or water year. The beginning is country-specific; in Germany, for example, it lasts from November 1 to October 31. For balancing in water management, however, snow in the mountains is a crucial factor; the first snow typically falls earlier in the fall in the Alps. In the high Alps, this snow sometimes already remains and then only enters the runoff in the spring of the following calendar year in the course of snowmelt.
In the hydrological year 22/23, precipitation also remained below average in total, even if the deficit was much smaller compared to the same period of the previous year. The foundation was laid with a winter that was clearly too dry; February in particular was extremely poor in precipitation in most of the country (especially the west and south). Spring was able to compensate for some of this. March was clearly too wet, and April also brought more rain than usual. For the glaciers, this was initially optimal in spring! May and June were again too dry, however, and the rising temperature level caused the protective snow cover to disappear again. The summer was warmer than average, with a few exceptions, the snow line was high during the thundery precipitations. From time to time it dropped towards 2000 meters, but this snow could never last long. Several times, the zero degree line rose above 5000 meters, so this season also turns out disastrous for the glaciers. The mass loss does not approach the extent of the previous year, but is clearly in second place.
Here now a few examples with the hydrological annual precipitation at certain stations:
Fig. 1: Precipitation between October 1, 2022 and September 27, 2023 at the Zurich-Fluntern station. 1004 mm/Norm 1108 mm; Source: MeteoNews
Fig. 2: Precipitation between October 1, 2022 and September 27, 2023 at the Bern-Zollikofen station. 854 mm/Norm 1022 mm; Source: MeteoNews
Fig. 3: Precipitation between October 1, 2022, and September 27, 2023, at the Geneva-Cointrin station. 799 mm/norm 946 mm.; Source: MeteoNews
Fig. 4: Precipitation between October 1, 2022 and September 27, 2023 at Davos station. 974 mm/norm 1046 mm; Source: MeteoNews
Fig. 5: Precipitation between October 1, 2022 and September 27, 2023 at Lugano station. 1421 mm/Norm 1567 mm; Source: MeteoNews
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