In order to design controllers for canals with inverted siphon especially for very long siphon, it is necessary to learn its response property. Compared to open canals, the water movement in inverted siphon is very different due to the fast travelling speed of wave and high water pressure. It is impossible to use openchannel model describe invert siphon section, and the delay caused by the siphon haven't been discussed in existing literature. This paper proposes a response model of inverted

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... on which contains a delay and an integrator in low frequencies, a constant gain in high frequencies. By comparing the response model to the results of simulation, this paper shows the response model is a good approximation. This paper studies a water distribution project consists of two canals and one inverted siphon. The result shows that the water level change at downstream end is significantly smaller than water change at upstream end. By applying response model of inverted siphon, this paper shows it is due to the delay of flow rate change from upstream end to downstream end.