Remodelling and Rehabilitation of Irrigation Outlets in Water Distribution of Canals in Punjab, Pakistan

Abstract

This paper highlights the problems associated with the outlets in the irrigation system of Pakistan, leading to the design of outlets, to trace the gradual evolution of various outlets types and to describe most of the types that have been evolved so far. The advantages and limitations of each type have been examined critically so that the selection of a type for any particular set of conditions may be rendered easy. An outlet is a flow measuring and controlling device between farmer’s land and an irrigation system. In Punjab about fifty thousand outlets irrigate an area of approximately 25.5 million acres annually. Improperly designed outlets may cause a number of problems such as variation in their coefficients of discharge, inequitable distribution of water, silting of canals, inadequate availability water at the lowest outlets, lack of incentives for saving of water and poor drainage. Field calibration of the irrigation outlets proved that their calibrated Cd. vary from the designed Cd. (0.6 for OF and 0.9 for AOSM), as outlets were not designed according to their designed parameters. Defective outlets were also the main cause of silting in canals. The pipe-cum-semi module was very helpful to draw silt from the bed of the parent channel in a case if we want a higher setting of outlet. 20% of canal water in Rabi season and 40% water in Kharif season were snatched by illegally Theft problem. In order to prevent theft, the outlets should be tamper proof and the irrigation department should adopt the legal procedure strictly. All over the world, the engineers and farmers designed and installed various kinds of farm outlets suiting their local conditions. Work is being carried out to make them structurally, hydraulically and economically fit. An attempt is made to bring all the information together leading to economical and efficient design of outlets and to look upon their possibility of adaptability in Pakistan.