Weather balance 2025: Only four times in the last 99 years has it been drier

2025 was the first calendar year in which the Ruhrverband was allowed to manage its reservoir system in accordance with the new, lower limits for the minimum water flow in the Ruhr - the North Rhine-Westphalian state parliament had passed the necessary amendment to the law in December 2024 after a long political struggle. And it soon became clear how urgently necessary this decision was: the year 2025, which had just ended, was one of the five driest that the Ruhrverband has recorded in its precipitation measurements dating back to 1927.

In order to maintain the minimum water flow in the Ruhr in 2025, the association therefore had to release large quantities of water from its reservoirs to the river system. However, almost 32 million cubic metres less than would have been necessary without the change in the law. In other words, to comply with the old limits, the Ruhrverband would have needed an additional volume of water last year that was roughly equivalent to the capacity of the Verse dam!

Overall, less than three quarters of the average annual precipitation fell (minus 27%). The early onset of the drought in February (minus 74 % precipitation) and March (minus 82 % precipitation) was particularly noticeable, because while these two months can usually be used to build up water supplies, in 2025 water had to be released from the reservoirs from March onwards to maintain the minimum water supply in the Ruhr. According to preliminary calculations, by the end of the year, the obligation to provide additional water at the Villigst gauge had totalled 182 days - almost half a year to the day. This is how long the water flow in the Ruhr at Schwerte would have been below the statutory minimum discharge if it were not for the Ruhrverband's dams. On around 30 days, the Ruhr near Schwerte would even have been completely dry.

A look at the temperatures once again confirms the trend that it is getting warmer and warmer in the Ruhr catchment area. Although the average temperature in 2025 was 9.8 degrees Celsius, below the 10-degree mark for the first time in three years, it was still 0.8 degrees too warm compared to the long-term average of the 1991 to 2020 time series. This puts 2025 in seventh place among the warmest calendar years since temperature records began 145 years ago.

Incidentally, the first six places in the warmth ranking are also all years since the turn of the millennium, including the three frontrunners 2022, 2023 and 2024. The bottom line is that climate change with its extreme weather phases is also the "new normal" in the Ruhre catchment area and will pose even greater challenges for critical infrastructure in the future.