Lake Dümmer reed marshland facility, Lower Saxony
Reducing the amount of phosphorus flowing into the lake
The primary objective of this project is the reduction of summer algal bloom in Lake Dümmer, Lower Saxony’s second largest lake. This requires the amount of phosphorus being transported to the lake by the Hunte waterbody system to be significantly reduced. Services provided included the planning and design of the necessary area of diked marshland, with all required structures and culverts, and the design of a controlled supply. On the basis of existing studies (a 1997 preliminary design and a 2012 framework design for the remediation of Lake Dümmer), the technical feasibility was verified and a detailed design was developed. This involved, in an initial analysis of options, comparison of three different solutions for the supply system feeding the reed marshland:
• Damming of the Upper Hunte river and discharge below the inflow of the Elze
• Diversion of the Hunte river via a pumping station
• Discharge of the Hunte river near Hunteburg and diversion via a supply channel and the Elze
In addition, various options for the approx. 200-hectare marshland were assessed with respect to space availability, ground management, environmental impacts, operational considerations, etc. Preferred options were then identified using a two-step value benefit analysis involving many criteria, and presented to the client and its expert committees.