A Statistical Analysis of Trickle Irrigation Uniformity

ABSTRACT TWO of the causes of trickle irrigation nonuniformity are variations in emitter properties and variation in pressure at the emitters. A simple algebraic equation for evaluating the combined effects has been previously proposed (Bralts et al., 1981a) for the case when both emitter and hydraulic properties are normally distributed and independent. A simulation model was developed to evaluate these assumptions for a simple lateral. First, it was found that the emitter and hydraulic properties are independent for practical purposes. Second, it was shown that the nature of the pressure distribution can have an impact on the assessment of uniformity. In terms of distribution uniformity, DU, assuming a normal pressure distribution for a single horizontal lateral gave lower (conservative) values of uniformity. A simple procedure is presented for developing an equivalent coefficient of hydraulic variation which will give a more accurate estimate of the combined effects. Finally, it is shown that the proposed equation only gives an estimate of the actual uniformity. The variation in this estimated combined uniformity (DU) is greater when it is caused by emitter variation than when it is caused by hydraulic variation, at least for this simple example. Thus this paper helps to refine analysis of irrigation uniformity for either the design or evaluation of trickle irrigation systems.