An anticipatory system is a system containing a predictive model of itself and/or of its environment, which allows the system to predict its future state. Such a system would be of great use for decision makers in water regulation. Our work has resulted in a prototype of an anticipatory simulation tool that functions as a decision support system for water regulation. The simulation tool simulates a simple water regulation system. First a model of a simple water regulation system was constructed. Based on that model the simulation tool was developed and improved by adding weak anticipation. Simulations with and without weak anticipation were run with real data. Evaluations of the simulations show an improved performance of the simulation tool when using weak anticipation compared to simulations without weak anticipation.