Hydraulic and Statistical Analyses of Design Emission Uniformity of Trickle Irrigation Systems

The important evaluation parameter in trickle irrigation is emission uniformity. There are two different methods to calculate emission uniformity; (1) field evaluation for the subunit and (2) using theoretical formulas to calculate emission uniformity during the design period. Emission uniformity is usually divided into two parts, namely, manufacturing, EUm, and hydraulics emission uniformity, EUh. The global emission uniformity is the product of these two parts. Previously, a formula was developed to predict the manufacturing emission uniformity by assuming that when the emitter is tested at a given head, emitter discharges are normally distributed around their mean. This assumption did not apply well to the tested emitters. In this research, the manufacturing part was expressed in terms of the statistical characteristics of the distribution of emitter discharges when tested at a given pressure head. The hydraulic part of emission uniformity, EUh, was expressed in terms of the hydraulic characteristics of the subunit. Many design cases were executed and for each design the matrix of emitters discharges and the hydraulic emission uniformity were calculated. The hydraulic emission uniformity was calculated by using the developed formula. The results obtained from the two methods were found to be closely related. The research involved conducting two sets of experimental work to test several types of emitters and the second set of experiments involved measuring actual emission uniformity of trickle irrigation systems to verify the theoretical formulas to calculate design emission uniformity. From the conducted experiments and the theoretical analysis it was found that for the tested emitters the distribution of emitter discharges, when tested at the same pressure head, around their mean was not normal; it is sufficient to test the emitter at a given head. The values of field emission uniformity were very close to those calculated by an existing and a developed formula. The developed formula provides a simplified method to calculate the hydraulic emission uniformity.