Operational Behaviour of Hydraulic Structures in Irrigation Canals in Sri Lanka

Abstract

The Hydraulic performance of structures provided for regulation in irrigation canals is influenced by many parameters such as type of flow control, type and frequency of adjustments, and topographical features of sub-systems that they are installed. The irrigation systems in Sri Lanka mostly designed for up-stream discharge control operation, with manually/mechanically adjusted gated structures, under steady state flow conditions. Further, topographical features of many gravity irrigation systems are varying at sub-system level due to presence of single and double bank reaches, inclusion of in-lined storage tanks. However, irrigation systems are operated under varying flow regime due to scheduled or unscheduled flows in water delivery. The adjustments of gates in structures in such situations are done by manually/mechanically by operators at different frequencies. Therefore these situations are analyzed by hydraulic simulations using SIC hydraulic model for three different topographical sub-systems under different frequency of adjustments. The actual performance in water delivery is evaluated by effective volume of water delivered, timeliness in water delivery, at the final delivery location while maintaining on-line water adequacy through delivery points along the canal. The results will provide guidance for operation of regulation structures for effective conveyance of water under varying flow conditions.