Sediment

Lake sediments play an important role for the nutrient cycling, especially in shallow, unstratified water bodies. Phosphor release by the sediments is often a main source for internal loading in eutrophicated shallow lakes. First investigations of the sediments of Alte Donau were done by Loffler (Alte Donau, Projektstudie im Auftrag der Wasserstrassendirektion, 272 pp, 1988). More detailed research was done prior and after the restoration of Alte Donau. The results of the investigations by Ripl (Sediment treatment. In: Eiseltova M (ed) Restoration of lake ecosystems a holistic approach, vol 32. IWRB Publication, Slimbridge, pp 75-81, ISBN 0-9505731-5-9, 1994) were used as the basis to establish the treatment process. Considerably low iron content of the sediment and a high proportion of organic content were of importance to use the Riplox method (Ripl W, Sediment treatment. In: Eiseltova M (ed) Restoration of lake ecosystems -a holistic approach, vol 32. IWRB Publication, Slimbridge, pp 75-81, ISBN 0-9505731-5-9, 1994) as the main restoration measure in Alte Donau. The aim of the investigations in 2004 was to evaluate the sustainability of the restoration measures and to create a data base recognizing undesirable trends like an enrichment of the organic content in an early stage. In this chapter the focus is set on the results of the investigations in 2004.