Evaluation of Microirrigation Uniformity on Laterals Considering Field Slopes

Water application uniformity is an important performance criterion that must be considered during the design and evaluation of the microirrigation systems. This study was conducted to evaluate the water application uniformity considering field slopes. The uniformity parameters including coefficient of variation (CV), Christiansen’s uniformity coefficient (UCC), distribution uniformity (DU), emitter discharge variation $q_{v\left(q\text{max}\right)}$ expressed by the difference between the maximum emitter flow rate $q_{\text{max}}$ and the minimum emitter flow rate $q_{\text{min}}$ to $q_{\text{max}}$ , emitter discharge variation $q_{v\left(qd\right)}$ expressed by the difference between $q_{\text{max}}$ and $q_{\text{min}}$ to design emitter flow rate $q_d$ , emitter discharge variation $q_{v\left(qd\right)}$ expressed by the difference between $q_{\text{max}}$ and $q_{\text{min}}$ to average emitter flow rate $q_{\left(\text{avg}\right)}$ , emission uniformity $\left({\text{EU}}_{\left(q\text{avg}\right)}\right)$ expressed by $q_{\text{min}}$ to $q_{\text{avg}}$ , and ${\text{EU}}_{\left(qd\right)}$ expressed by $q_{\text{min}}$ to $q_d$ . Furthermore, the relationships of CV versus UCC, CV versus DU, CV versus $q_{v\left(qd\right)}$ , CV versus $q_{v\left(q\text{max}\right)}$ , CV versus $q_{v\left(q\text{avg}\right)}$ , CV versus ${\text{EU}}_{\left(q\text{avg}\right)}$ , and CV versus ${\text{EU}}_{\left(qd\right)}$ were also discussed. The results of the study revealed that the field slope does not obviously affect the relationships of CV versus UCC, CV versus $q_{v\left(q\text{max}\right)}$ , and CV versus $q_{v\left(q\text{avg}\right)}$ for any of the slopes evaluated, which include uphill, zero slope, and downhill. Furthermore, the effect of slope on the relationships of CV versus ${\text{EU}}_{\left(q\text{avg}\right)}$ , CV versus ${\text{EU}}_{\left(qd\right)}$ , and CV versus $q_{v\left(qd\right)}$ was obvious, especially when large downhill slopes with a $\text{CV}>0.05$ were considered. However, the effect of slope on the relationships of CV versus DU was intermediate. Taken together, the results of this study indicated that the UCC, $q_{v\left(q\text{max}\right)}$ , and $q_{v\left(q\text{avg}\right)}$ should be recommend in addition to CV when evaluating the water application uniformity of the microirrigation systems, regardless of slope, and that $q_{v\left(qd\right)}$ and ${\text{EU}}_{\left(qd\right)}$ should be recommend when evaluating systems placed in fields with a slope of zero or an uphill slope.