Determination of optimum furrow length and Application of SIRMOD Model in Furrow Irrigation Simulation

Surface irrigation is the most irrigated area in the entire country. Therefore, it is necessary to evaluate this irrigation system due to improve irrigation efficiency. One of the existing software for assessing surface irrigation methods is SIRMOD model. In this study, a few models in the SIRMOD package were evaluated. In hence, three data groups of research stations of Kabutarabad (Isfahan), Hashem Abad (Mazandaran) and Zarghan (Fars) were used as local inputs. The soil texture of these fields was silty clay loam, silty clay loam and silty clay respectively. First, the length of the Furrow was investigated by using three methods FAO, SCS and W&S. Optimum Furrow length in these areas was determined as 120, 200 and 100 meters, respectively. The results of reliability indices such as NRMSE, ME and R2 were used to compare simulated and measured values of the parameters which indicated the high accuracy of the models those have performed well in predicting advanced and recession time in furrow. The results also revealed that the hydrodynamic model was more accurate than the two zero-inertia and kinematic inertia models in predicting advanced and recession times. According to the results of this study, the highest error of these models was related to estimating the amount of runoff at 5% and the lowest was related to the infiltration depth parameter at 2.7%. Therefore, the models in the SIRMOD package estimate the cumulative infiltration rate in the soil to be higher than the runoff rate.