The reservoir of the Isenach, which lies about 5km below the spring, was dammed in 1736/37 in order to ensure a steady flow of water. This was important for the graduation works which were also built in Bad Dürkheim in 1736.
The entire Isenachweiher has about 17,850 m². What is perceived by the observer as the actual surface of the lake extends about 50m in width and 100m in length. During a trip in a rowing boat (available for hire), you may be lucky enough to spot a beaver or two, as there has been a small beaver territory there since the end of 2017.