Barb Losses of Four Common Types of On-Line Trickle Irrigation Drippers in Iran

Computation of hydraulic head variations due to changes in elevation and friction along a lateral is needed for accurate design of drip irrigation. This study was carried out to evaluate trickle irrigation emitter barb losses for different types of on-line trickle irrigation emitters using 16 mm lateral pipes. Four common types of on-line trickle emitters used in Iran with standard discharge rate of 4 l/h were studied under different lateral discharges ranging from 0.8 l/s to 0.19 l/s corresponding to the velocities of 0.6 m/s to 1.5 m/s, respectively. The amounts of head losses along the laterals were measured for 11 different flow velocities in four replications using two digital pressure gauges. The results showed that about 12% to 16% of the head losses in lateral were due to the existing emitter barbs. The well-known Keller graph was also used to estimate the emitter barb losses and the findings were compared to the experimental results. The maximum amounts of mean absolute error (MAE) and root mean square error (RMSE) were equal to 4.768 and 0.4947, respectively, for the emitter No.1, the minimum amounts of these criteria were 0.7237 and 0.0817 for the same order for the emitter No.4. The results indicated that the estimated head losses via Keller graph had not enough accuracy for on-line emitters which are widely used in Iran.