A New Technique to Improve the Emission Uniformity for Trickle Irrigation Systems

Abstract

The trickle irrigation method is a relatively new watering technique which has proven to be a progressive, successful development all over the world. Benefits of using this method in vast areas of Iraq are obvious, especially in parts of drought areas where development and reclamation necessitate the use of trickle irrigation. Previous field research has improved the emission uniformity ( EU ) of trickle irrigation to 100% by individually elevating emitters above the lateral line. In this research, a simpler procedure was proposed for improving EU . This procedure raises the inlet of the lateral pipe to a desired height above ground level. The increasing energy due to elevation drop along the lateral compensates for friction loss, resulting in a more consistent pressure distribution in the pipe. The objective of this research was to improve the resulting EU and to provide a method for determining the optimum inlet height. If tension is placed on the lateral such that its slope is zero at the end of the lateral, its profile becomes a catenary (a hyperbolic cosine function). A hydraulic analysis was performed to estimate flow for each emitter and the resulting EU . Setups that were used in the previous research were simulated. Lateral elevations at the emitters were similar to the elevations of the raised emitters in the previous research, since both approaches were based on the same hydraulic idea. While 100% was not achieved, all EU 's were over 99%. The hydraulic analysis was also used to evaluate the effects of inlet elevation and emitter exponent on EU . It was found that the EU increases when the height of the inlet lateral pipe increases up to a maximum EU , correlating to an optimum design inlet elevation, before it starts to decrease again. Raising the inlet to the optimum elevation caused the EU to increase from 95 to 99.5% compared to leaving the lateral pipe on the ground. The emitter exponent had a negative correlation with the estimated EU , indicating that emitters with lower emitter coefficients may be preferable when designing trickle irrigation systems for maximum EU . The developed procedure for trickle irrigation systems can be used to execute designs of lateral pipe lines that maximize EU .