Control of the eutrophication of the reservoir of Esch-sur-Sûre (Luxembourg): evaluation of the phosphorus removal by predams

摘要

The phosphorus retention capacity was established for two predams having the same water supply and the same seasonality but with contrasting hydraulic retention times and phosphorus loads. The annual retention of total phosphorus of the shallow Misère predam amounted to about 60%, whereas the deeper Bavigne predam retained about 82%; for soluble reactive phosphorus (SRP) the annual retention rates were 4 and 54%, respectively. The different behaviour of the predams is probably due to their different flow regimes and morphology. The highest retention rates were observed during summer, when up to 90% of SRP could be retained in the Bavigne predam. The comparison of the measured removal rates of SRP with those calculated on the basis of the model proposed by Benndorf & Pütz (Wat. Res. 1987 21: 829–838) shows a rather good agreement for the thermally stratified Bavigne predam. For the shallow Misère predam, the model adequately predicts the annual trends of SRP removal, but a great discrepancy is observed for the absolute values. This is probably due to the phytoplankton composition and to the release of phosphorus from the sediments in the summer period.