Introduction of flap gates for anicuts in wet zone

Water diversion mechanisms are commonly used in the irrigation systems and this concept is older than tank (reservoir) systems in Sri Lanka. At present, for water diversions in the wet zone anicuts are constructed by using lifting type gates. Anicuts are used to maintain required water level in the upstream by releasing only the excess water to downstream. In the lifting gate, water is allowed to flow from the bottom and this causes high erosion in the canal. The thrust force due to water pressure on the lifting gate makes it difficult to operate the system and then controlling the system is a complex task. This paper describes the construction and operation of newly introduced flap gates and issues related to lifting gate which are presently used for diversion process. In this analysis, conceptual design of a flap gate with compressive arc type wall plate is proposed to minimize use of construction materials. In the proposed system, height of the anicut could be changed from the top and then the water level in the upstream is not varied much when compared with lifting gates for varying flows in the cannel. According to the practical experiences from implemented proposed systems, controlling of the system is much easier compared to the conventional system.