A new suit for the IJsselmeer: Possibilities for facing the future needs of the lake by means of an optimized dynamic target water level

A new suit for the IJsselmeer: Possibilities for facing the future needs of the lake by means of an optimized dynamic target water level

Talsma, J.

Van de Giesen, N.C. (mentor)

Civil Engineering and Geosciences

Watermanagement

Water Resources

2011-03-31

Introduction and problem definition The IJsselmeer is located in the center of the Netherlands. For its relevance for the Dutch economy and society, it is often addressed as the Wet Hearth of the country. When looking into the future, the IJsselmeer is under climate threats. Wetter winters will bring more water into the system, in combination with sea level rise, and lower gravity discharge to the Waddenzee. This will generate safety issues. On the other hand summers will be drier, putting the satisfaction of water demand in danger. Research approach and research question The goal of the research is to define for the IJsselmeer a dynamic target water level which is variable through the whole year by means of an optimization approach. The optimization uses a single objective function considering dikes safety and water demand. Such approach has been chosen because follows a different path than the ones mainly used so far to tackle the issue. When management measures alone are not enough to define a climate-proof IJsselmeer, extra measures are taken into consideration: a pumping station at the Afsluitdijk and early storage in March. The main research question asks for an evaluation of the optimization methodology used to define efficient alternatives for the IJsselmeer. The sub-question requires the assessment of the flexibility of the IJsselmeer towards a climate-proof system, and the definition of extra measures, when needed. Methodology The definition of the optimum measures is achieved in several steps. Firstly the objective of the problem owner is defined. The Dienst IJsselmeergebied is the only problem owner. Its interests are safety and water demand satisfaction. Then indicators are derived from the objectives, and merged into the objective function. Classes of measures are selected, and a model of the system designed for their evaluation. Finally the optimization problems are defined in order to design the optimum alternatives. Results A different planning of the target water level alone is not able to satisfy the needs of safety and water demand on the long term. As it is now, the IJsselmeer is flexible on the short term, but not enough to accommodate the impacts of longer horizons: extra measures are needed in order to define a climate proof system in 2050 and 2100. Pumping station at the Afsluitijk is an effective measure to guarantee safety for all the scenarios. Early storage in March is effective in the medium horizon (2050) but need high target water levels along the summer for the long term (2100). This might generate safety issues. Even if applied on a simplified case, the use of an optimization methodology manages to define a realistic picture of the flexibility of the IJsselmeer, and retrieves efficient options for possible future strategies. For this reasons, the present research can be considered a successful implementation of an optimization approach for the IJsselmeer. Conclusions and recommendations For the short term it is recommended to use the flexibility of the system, implementing the changes in summer target water levels which would allow deeper satisfaction of water demand. For the medium/long term, options for early storage need to be investigated together with the summer target water levels needed. This would probably require reinforcement of the dikes. Options for safety can be then defined for the new reinforced system, considering combinations of pumping station and raise of the dikes. A more extensive and detailed optimization tool should be realized for the IJsselmeer, and applied for the definition of the measures above. In particular it is recommended to use a multi-objective analysis and include costs in the definition of the indicators.

optimization
dynamic target water level

http://resolver.tudelft.nl/uuid:f97a2a79-a3bf-4bcc-b0a6-819e70ccd62b

2011-05-04

Student theses

master thesis

(c) 2011 Talsma, J.