Sedimentmanagement Altmühlsee

Lake Altmühl, part of the Middle Franconian Lake District, is an artificial water body to improve the hydrological quality of the low-precipitation catchment area of the Main by diverting water from the Danube catchment area. However, Lake Altmühl is only actively fed in the event of flooding via a diversion from the Altmühl river, and this results in very artificial runoff and sediment dynamics. The problem that has developed here in recent years is a very high input of nutrients into Lake Altmühl, associated with the fine sediments. Due to the shallow water depth (max. 3 m), these very high fine sediment loads and nutrient deposits are very mobile, and even moderate winds cause them to be stirred up and rearranged. With the rising water temperatures due to climate change, algal blooms have occurred in the recent past, resulting in repeated bans on swimming in this lake, which is also very popular with tourists. BOKU is now tasked with developing a sustainable (fine) sediment management in cooperation with the universities of Bayreuth, Munich, and Nuremberg. BOKU's specific task will be to use modeling and measurement of sediment transport (core expertise at BOKU) to create a basis for decision-makers, who must then bring a cost-benefit optimized approach to the issue of fine sediment and nutrients to the political stage. The project has a timeframe of one year. In addition to the modeling, four to five field surveys are planned. These will be used to measure water temperature and determine fine sediment loads during an incoming flood wave. Cores of the fine sediment deposits have already been extracted externally by the company UWITEC, and these will also be analyzed by BOKU.