Trickle irrigation systems’ efficiency depends on system uniformity, which is determined by water discharge uniformity from emitters. It is impossible to produce 2 identical emitters due to manufacturing variations. The manufacturer’s coefficient of variance is used as a measure of discharge variations of emitters. | Turk J Agric For 28 (2004) 223-230 © TÜB‹TAK Determination of Hydraulic Performance of Trickle Irrigation Emitters used in Irrigation Systems in the Harran Plain Halil KIRNAK* University of Harran, Agriculture Faculty, Irrigation Department, 63200, fianl›urfa - TURKEY Ergün DO⁄AN University of Harran, Agriculture Faculty, Irrigation Department, 63200, fianl›urfa - TURKEY S›dd›k DEM‹R University of Harran, Graduate School of Natural and Applied Science, 63200, fianl›urfa - TURKEY Sabri YALÇIN Göktepe Co., 63200, fianl›urfa - TURKEY Received: Abstract: Trickle irrigation systems’ efficiency depends on system uniformity, which is determined by water discharge uniformity from emitters. It is impossible to produce 2 identical emitters due to manufacturing variations. The manufacturer’s coefficient of variance is used as a measure of discharge variations of emitters. In this study, manufacturers’ reported discharge rates and coefficients of manufacturing variation (CVm) values were compared with test results for various types of in-line emitters manufactured by 4 different companies in Turkey. A total of 9 drip irrigation lines, comprising 7 non-compensating and 2 compensating emitters, were tested at 50, 100, 150, 200 and 250 kPa pressures. Non-compensating emitter types were not tested at 250 kPa. Compensating emitter exponents ranged from to while non-compensating emitters’ values varied between and . Test results showed that only 1 of the 7 non-compensating emitters and both compensating emitters had flow rates within ± 10% of manufacturers’ reported values. The t-test between manufacturers’ reported and measured mean flow rates at manufacturers’ reported nominal operating heads showed that there was no significant statistical difference at the α 15 excellent average marginal poor unacceptable Emitter exponents The emitter is the most important part of drip irrigation tubing. An emitter with a high degree of pressure compensation