Lake Constance reaches exceptionally low September level
Water level well below seasonal average, but not an all-time low record.
Lake Constance is exceptionally low at the end of September. At Konstanz, the daily average in mid-September fell below the lowest level recorded there for that date since 1850, while official measuring stations at the end of September were almost one metre below the seasonal average.
Baden-Württemberg’s Niedrigwasser-Informationszentrum measured a daily average of 265 centimetres at Konstanz on 15 September. That was 86 centimetres below the average for that date in the 1991–2020 reference period. The level was also below the previous minimum for 15 September, recorded in 2003.
The measurement series requires some precision. This is a record for that date, not the lowest water level ever recorded. The lowest level in the full series since 1850 was 226 centimetres, recorded in late February and early March 1858. Lake Constance normally reaches low levels in late winter or early spring.
Swiss measuring stations also show that the water level remains low. At Romanshorn, the level stood at 394.72 metres above sea level on 29 September. That was 99 centimetres below the median for the same calendar day in the 1991–2020 period. The figures are not directly comparable with the Konstanz measurement, because the stations use different reference points and units.
A low water level has consequences for shipping and for ports and moorings. Whether a particular service can operate, however, depends not only on the level of the lake. Local conditions on the lakebed, access to a port, wind and up-to-date information from operators also play a role.
The low level is consistent with the dry conditions measured this year in southern Germany and parts of Switzerland. A measurement series on its own does not show which individual weather factor is responsible. That requires data on rainfall, inflow from rivers, evaporation and developments over a longer period.
Lake Constance is therefore primarily a clear indicator of water scarcity at present. For climate interpretation, the longer series is more important than a single exceptional month. The measurement does show that water management, shipping and the regional economy can become vulnerable when low water levels occur outside their usual season.
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The water levels and reference periods were checked with German and Swiss measuring authorities. The article avoids claiming an absolute record and makes clear which measurements are not directly comparable.
- confirmed The daily average at Konstanz was 265 centimetres on 15 September. — Baden-Württemberg NIZ low-water report. source
- confirmed The level was 86 centimetres below the average for that date. — NIZ compares it with 351 centimetres in 1991–2020. source
- confirmed The absolute record low in the measurement series is 226 centimetres, recorded in 1858. — Mentioned in the German hydrological overview. source
- confirmed The level at Romanshorn was 394.72 metres on 29 September. — Official Swiss hydrological measurement data. source
- confirmed The level at Romanshorn was 99 centimetres below the median for that date. — Comparison of the lake level with the 1991–2020 period. source
Editor's note
The measurements are well substantiated. The distinction between a date record, a seasonal deviation and the absolute record low is made explicit; the cause is not elaborated beyond what the sources allow.Sources
- NIZ-Lagebericht Gewässer — Niedrigwasser-Informationszentrum Baden-Württemberg
- Rivers and lakes: stations and values — Bundesamt für Umwelt Zwitserland
- Lake Constance – Annual Comparison & Records — Seepegel