<p>Due to diversions to the hydroelectric power stations on Lake Achen and Lake Walchen, the Upper Isar has suffered a considerable water shortage since the 1920s. In 1959, the Sylvenstein reservoir was put into operation to allow low water levels to be raised. The active storage of the Sylvenstein Reservoir is not sufficient to compensate a hundred-year flow deficit in Munich. It is not possible to expand the active storage, as this would reduce the flood storage, which must be available to protect downstream residents from a hundred-year flood. It is therefore also planned to use the Lake Walchen specifically to increase the low water level for the Munich conurbation, as most of the water that is withdrawn from the Isar is temporarily stored here. Hydrological studies also show that the existing flood storage at Lake Walchen is not sufficient. Two proposals for the future management of Lake Walchen are presented, which attempt to reconcile the partly competing uses (electricity production, flood protection, low water protection) in the best possible way. The multifunctional network system of Sylvenstein Reservoir and Lake Walchen enables the provision of services of general interest (flood protection and low water elevation) without significantly impairing electricity production at Lake Walchen.</p>