The Ruhr needs water from the reservoirs early in the year

The months that are usually used to dam up the reservoir system for necessary water releases in the summer months have brought extremely little precipitation to the Ruhr catchment area this year. According to the Ruhrverband's records, the two-month period of February and March was drier than it had last been in 1929. Only 21 mm of precipitation fell in February and just 14 mm in March - a total of 35 mm, which is just 22% of the long-term average for this period.

In response to the dry weather, discharges in the Ruhr catchment area have been in the low water range since the end of February. At the Lenne gauge in Hagen-Hohenlimburg, the daily average discharge was below the low water discharge (NQ) recorded for this period on almost half of all days in March (14 out of 31). The lowest value was recorded on 28 March 2025 at 6.70 m³/s. This trend has also continued since 2 April with discharges below the lowest daily average value determined for this gauge for the month of April.

At the Ruhr gauge near Hattingen, the discharges are still above the lowest daily average values recorded at this gauge in the long-term observation. In contrast, a new NQ value of 20.8 m³/s was recorded at the Ruhr gauge in Mülheim on 26 March this year; the previous NQ value in the long-term observation was 21.2 m³/s in 1991.

Due to the low water levels, the Ruhrverband is currently subsidising its dams to ensure compliance with the minimum discharges in the Ruhr prescribed by the Ruhrverband Act. In March alone, there were eleven days requiring subsidies at the Villigst (Ruhr) gauge - the second-highest number for this month since the introduction of the minimum flow limits in the Ruhr Association Act 35 years ago. So far in April, there have been 9 days at the Villigst gauging station that require a contribution, which is already more than the long-term average of the 1991/2024 time series. The result: unlike usual at this time of year, the reservoir level rose only slightly between 1 February and 7 March (from 86.8 to 87.5 % of full) and then decreased until today, 10 April (to 85.9 % of full). Nevertheless, there is no need to worry about the water supply; the reservoir system is also well positioned for further dry months to come.

Another look at the temperatures in the Ruhre catchment area: the average monthly temperature in February was 0.3 degrees too warm compared to the reference period 1991/2020, and in March it was even 1.3 degrees too warm. The trend towards ever higher average temperatures is thus unbroken; December 2024 and January 2025 were also warmer than the respective reference period. And at 10.5 degrees, the runoff year 2024, which ended in November 2024, even reached the highest annual average temperature in the Ruhre catchment area since weather records began over 140 years ago.