In 2002, a limnological office was commissioned to collect the ecological key data on the lake. A local council decision led to the results being published. They state that the main reason for the nutrient pollution is an increased phosphorus content caused by inflowing groundwater. The phosphorus probably originates from debris that was dumped into the lake after the bomb attack on Freiburg during the Second World War and the debris contained remains of phosphorus bombs, 255 tonnes of which were used during the attack. The lake used to be further to the East, in the same place where the track used to move debris after the War ended.