Low water brings more seagrass problems for Lake Constance boaters
Sunday 9th August 2026 on 09:30 in
Austria
Low water levels and high temperatures are causing more seagrass to accumulate on Lake Constance, creating challenges for boat operators, ORF reports. The water quality for bathing remains excellent at all sites tested by the Vorarlberg Institute for the Environment.
Roland Schwendinger, harbour master and leaseholder of the fuel station operated by the Schwedenschanze Motorboat and Sailing Sports Club, said boats are more frequently pulling water plants from shallow banks because of the low water level. The seagrass then gathers in larger fields on the surface.
If it is not removed, the plants can become caught in propellers. Boats may lose power or, in the worst case, become unable to manoeuvre. The vessel “Seekuh” and the Schwedenschanze club are therefore regularly removing larger accumulations.
Bathing water quality remains excellent
The current conditions have not affected Lake Constance bathing water quality. Gerhard Hutter of the Vorarlberg Institute for the Environment said water samples are taken on five dates between the end of June and the end of August at 16 bathing sites. The latest test, conducted on July 20, found excellent bathing water quality at every site examined.
The assessment uses various indicators of bacterial contamination. According to Hutter, high temperatures and strong sunlight can even have a positive effect because they reduce the bacteria’s chances of survival. The low water level therefore has no direct impact on bathing water quality.
Higher risk of swimmer’s itch
Hutter said the lower water level does have other consequences. Aquatic plants reach the surface earlier and grow more extensively in shallow areas and bays. Bathing, swimming and wave action can cause them to be torn loose and washed onto the banks as seagrass.
Areas with many aquatic plants also attract more snails and waterfowl. Under favourable conditions, this can increase the spread of cercariae, which can cause swimmer’s itch in people. The low water level also raises the risk of injuries in areas of the shore covered with mussels.