On 21 September 2026, the average daily discharge of the Rhine at Basel-Kleinhüningen was lower than 1% of all measured daily discharges since 2020. The daily mean was 384 m³/s, with a minimum of 228 m³/s and a maximum of 543 m³/s. These are exceptionally low values: the maximum discharge ranked 14th over the last 30 days, 17th among all September days since 2020, and within the lowest 1% of all days since 2020.

Over the past 30 days, the highest discharge was 817 m³/s on 22 August 2026, and the lowest was 291 m³/s on 8 September 2026. The current flow is therefore well below even the lowest values of the preceding month. Table 2 lists the months with the lowest flow conditions since 2020; September 2026, with a minimum average flow of 384 m³/s, is the lowest on record for this period, followed by August 2026 at 413 m³/s and August 2022 at 436 m³/s.

Low water levels on the Rhine have consequences that reach well beyond the river itself. Cargo vessels have to reduce their load to stay clear of the riverbed, so more trips are needed to move the same volume and transport costs rise sharply, with the effect passed on to industries that depend on the waterway for coal, oil products, chemicals and grain. The shallower water also heats up faster in summer. Warmer water encourages bacterial growth, which can produce noticeable odors, and it holds less dissolved oxygen. The combination of higher temperatures, lower oxygen and more concentrated pollutants degrades water quality and can lead to fish kills. Swimming is generally discouraged under these conditions because of the higher bacterial load. Further effects include restrictions on power plants and industrial sites that draw river water for cooling, since they may no longer discharge warmed water without exceeding temperature limits, reduced dilution of treated wastewater, pressure on water supply and irrigation in the surrounding area, and falling groundwater levels along the river that affect riparian vegetation and wells.