Abstract: WES (Waterway Experiment Station) compound weir is evolved from WES weir by adding a flat segment on the crest. Different WES compound weirs are formed by changing the crest thickness and the upstream weir height. In the present research,it is classified into WES compound practical weir and WES compound broad-crested weir according to the change of flow regime and flow oefficient. The standard to classify the WES weir into high weir and low weir in consideration of the crest thickness is also discussed. In addition,the fitting formulas of discharge coefficient under design water level are given for the above weir types. This research lays a foundation for further researches.

Key words: WES compound weir , discharge coefficient , practical weir , broad crested weir , high weir , low weir