Assessment of the performance indicators and input variables of border irrigation system

The most common of irrigation method in the world is surface irrigation, so that 94 percent of land is irrigated by this method. Many researchers say that low-efficiency surface irrigation is not related to the type and nature of surface irrigation, but also of weaknesses in the design, implementation and management. Many researchers say that low-efficiency surface irrigation is not related to the type and nature of surface irrigation, but also of weaknesses in the design, implementation and management of it. Management of surface irrigation is a complex engineering problem due to spatial and temporal variation of several affecting parameters. However researchers have individually studied the influence of each parameter on the efficiency of surface irrigation systems, but the combined effects of the parameters have not been investigated. Therefore, this study was conducted to evaluate the efficiency of the border irrigation system under simultaneous variation of two input parameters using Full Hydrodynamic Method of SIRMOD model in a silty loam soil. SIRMOD requires input parameters that measurement accuracy of this is effective on the accuracy of the simulation model. The unit flow rate, slope, length and cutoff time were used as input parameters. In order to assess the performance of the model unit flow rate, slope, length and cutoff time were changed ±25% and ±50%. About cutoff time, because of it must be the correct fraction of a day, therefore cutoff time 2, 3, 4, 6 and 8 hours in a day were considered. Also, to evaluate the efficiency of border irrigation, the Ea and DU indexes were used. The results of the study showed that the highest Ea (94.8%) was obtained for the unit flow rate of 1.5 (lps) and cutoff time of 180 minutes. The maximum DU (98.6%) was obtained for the two-parameters of cutoff time of 480 minutes and a slope of 0.006 (m/m). The influence of the unit flow rate on the performance of border irrigation was higher than other parameters. The results showed that can be considered value 2 (lps) and 240 meters as the unit flow rate crisis and length crisis for a silt loam soil respectively. The combination of unit flow rate and cutoff time can be selected as optimal combination to achieve high efficiency in border irrigation.