Investigation of the accuracy of infiltration measurement Non- point methods in designing of Furrow irrigation system

Background and Objectives: Infiltration is the most critical and often most difficult parameter for evaluation of surface irrigation systems. In particular, the infiltration specification is variable with time and place. In general, a fairly large number of field measurements is needed to show the average farm condition. The aim of this research is the investigation of the accuracy of extraction the type cumulative infiltration equation by using the Non- point methods and the adjusted by the irrigation process, in simulation of the closed end furrow irrigation system. For simulation, was used from the zero inertia model in WinSRFR software and the zero inertia and Hydrodynamic models in SIRMOD software.
Materials and Methods: This research was implemented at two farms whose names were 201E and 201C1, in the Hafttape Cultivation and Industry of Sugarcane that Sugarcane was cultivated in furrows floor. In each farm 7 consecutive furrows selected. Even furrows test and odd furrows had buffer roles. The average furrows length was in 201C1 farm, 268 meters and in the 201E farm 165 meters. In the both farms Longitudinal slope of the test furrows was measured and 0.001 (meter/meter) obtained and furrows width, 1.5 meters. The furrows were irrigated by closed end method. In order to prepare the data for the advance and recession, was put the station in the furrows length intervals of 20 meters. In both farms, three irrigations were evaluated. For measurement of the inlet flow rate to the test furrows, was used from WSC flume, type 3. Kostiakov Louis type cumulative infiltration equations obtained by the inflow – outflow method for both farms. By using the Advance and recession data and the volume of inflow water and infiltration to the furrows the type cumulative infiltration equations was adjusted and the adjusted cumulative infiltration equations obtained for each furrow. Then the amounts of the advance of the each irrigation for both farms simulated by using the type cumulative infiltration equations and adjusted and the hydrodynamic and Zero inertia models of both WinSRFR and SIRMOD software.
Results: Results of this research showed that placement the amount of infiltration experiments flow rate in SM software improves significantly the simulation process. Compare the results of the Zero inertia and hydrodynamic models of SM software shows that results of these models in simulation of the closed end furrow irrigation process with Sugarcane Cultivated in furrows floor, were similar and had little difference together. Evaluation of the result of SM and WS software simulations shows that if the type cumulative infiltration equations used in the advanced accuracy of process simulation in the 201C1 farm, had the good and moderate ranking and in the 201E farm, had the weak rank. Adjusting the infiltration equations and using them in these software upgrade accuracy simulation in the 201C1 farm to excellent ranking and in the 201E farm to the good and moderate range. This increase of accuracy was the improvement of the average of Relative Absolute Error index in the 201C1 farm 63 percent and in the 201E farm 53 percent. Results too showed that the SM software in simulated of both farms with the fewer Mean Square Error and the fewer Relative Absolute Error had better performance and both software have predicted Computing advanced times more than the real amount them.
Conclusion: In general results of this research shows that if the adjusted infiltration equations used Instead of the type infiltration equations in the designing, simulation and evaluation of the closed end furrow irrigation systems, increased the accuracy of results to significantly, finally will cause the improvement and increasing of the irrigation systems hydraulic indexes.