Evaluation of Direct Methods and Computer Models in Estimating the Infiltration Parameters of the Kostiakov-Lewis Equation in Sugarcane Fields

Surface irrigation systems are the oldest and common irrigation method. Surface irrigation is of low cost and energy requirements compared to sprinkler and drip irrigation systems. In general, a main large number of fields' data is needed to show the farm average condition. Infiltration parameters are one of the most important parameters in surface irrigation systems and it has led to increase the irrigation systems efficiency, especially since the characteristics of infiltration vary with time and place. The modified kostiakov-lewis equation is one of the most useful infiltration equations in surface irrigation. In the current study, the infiltration parameters of the modified kostiakov-lewis equation were determined with two sets of usual methods including direct methods such as two-point Elliot and Walker and Input-Output, computer models such as SIPAR_ID and IPARM. Finally, the results were compared with the results of field experiments.

The current field was irrigated three times from 14 September to 31 October 2016 at the R 5-22 farm located in Salman Farsi Agro-Industry sugarcane fields with age of Raton 2. To collect the required data, the fields experiments were conducted on nine furrows of 250 m in length, 1.83m in space and 0.04% in slope, which all furrows were irrigated under three events and three inflow (1, 1.5 and 2 l/s), and fields’ data were obtained from experimental measurements during summer and autumn2016 at sugarcane fields of Salman Farsi Agro-Industry %. In the current study, the inflow rate and runoff were measured by W.S.C type 1 and 2 and all furrows divided into 10 stations. The advane time and infiltrated depth were measured at each stations. In this study 18 furrows were considered, nine furrows were used for testing and the other furrows had buffer roles. The furrows were irrigated by closed-end method. In this study, three indicators of infiltrated volume in the root zone, advance time and runoff volume were used to evaluate the accuracy of estimation of infiltration parameters. Surface irrigation model: WinSRFR 4.1.3 was used to simulate irrigation phases and infiltration value in each method. In this study, zero inertia model was used for simulation.

Results of this study showed that using the direct methods to estimate the infiltration parameters in WinSRFR 4.1.3 software improves the simulation process significantly. The results of the Two- Point and Input-Output method were showed a little difference with the results of the WinSRFR 4.1.3 software in simulation of the closed-end furrow irrigation process with sugarcane cultivated in furrows. The direct methods for infiltration parameters in furrow irrigation showed more accuracy than computer models in advance time , runoff and infiltrated water volumes. According to the results of this study, the Two-Point method in estimation of advance time with mean of RMSE, MAE and RE of 10.52, 14.91 and 10.1%, infiltrated water volume with mean of RMSE, MAE and RE of 9.6, 7.36 and 7.8 and runoff volume with mean of RMSE, MAE and RE of 8.8%, 8.7% and 1.2%, had a very acceptable performance. Also, the RMSE and RE values of other direct method (input-output method) were 11.4% and 6.8% for infiltrated water volume, respectively, and 1.6 and 0.3% for runoff volume, respectively, shows that this method has high accuracy in estimating these two performance indicators although this method with an average of 25.11% and 27.2% was not able to accurately simulate advance time. On the other hand, the results of computer models showed that the IPARM model with the average mean absolute error and relative error was 23.33, 15.5% of the advance time, 20.02 and 26.7% of the infiltrated volume and 11.81% and 1.8% estimated runoff volume, which was better than the SIPAR_ID model. Although computer models had acceptable performance in estimating infiltration parameters, direct methods performed better due to the use of more input data and data from all stages of irrigation. In general results of this study were showed that, if the direct methods for infiltration equations used Instead of the computers models in the designing, simulation and evaluation of the furrow irrigation systems, increased the accuracy of results to significantly and will improve and increase irrigation performance indicators