CALIBRATION OF DIFFERENT WATER COURSE OUTLETS AT RAHUKI DISTRIBUTARY

Abstract

The calibration of various types of outlets plays pivotal role in ensuring accurate and equitable distribution of water. A study was conducted to calibrate three different types of outlets including orifice type semi module (OSM), pipe outlet and open flume (OF) off taking from Rahuki distributary. These types of outlets are commonly found in the irrigation system of Pakistan, particularly in Sindh. In this study theortical discharge was computed from geometrical parameters of outlets, actual discharge was measured through cut-throat flume. The values of coefficient of discharge (Cd) for all the outlets were calculated from minimum and maximum heads of the selected outlets. The results showed that the open flume outlet and adjustable proportional module produced higher Cd values as compared to pipe outlet. Hence open flume and adjustable proportional outlets could be used for higher accuracy. It was found that Cd values have direct relationship with upstream head at outlet as head increased, Cd values of all types of outlets increased. This study also developed an explicit empirical equation for all the outlets and rating curves on the basis of Cd values. The results of this study can be used as guidelines for agriculture engineers as well as Farmer’s Organizations (FOs) for proper operation of watercourses.

Keywords

• calibration of outlets
• coefficient of discharge and Stage discharge ratings