Field assessment and analysis of border irrigation systems with WinSRFR software (Case study: Urmia Plain wheat fields)

Due to the large number of parameters affecting surface irrigation and their temporal and spatial changes, surface irrigation management is very complicated in obtaining high efficiency and uniformity. Therefore, improving the irrigation performance based on variables with minimum implementation cost, ease of use, and the possibility of implementation in the field, is essential, and due to the high losses in surface irrigation, it is necessary to use tools that can maximize water efficiency with proper planning. Achievement is inevitable. Considering the current conditions of Lake Urmia due to its environmental crisis, the lack of water, and the importance of saving the lake from the current situation, one of the basic ways is to increase the efficiency of surface irrigation in fields. Therefore, the objectives of this research are a detailed examination of actual efficiency, calibration, and verification of WinSRFR software for the region, evaluation of the performance of the software in estimating the advance time parameters, and Evaluation of the software in estimating the efficiency of water use. In other words, the main goal is to evaluate the irrigation performance and achieve the appropriate performance through proper management so that we can move towards this goal with proper design. To achieve the aforementioned goals, field evaluation was done during the wheat growing season.
 
Materials and Methods
To collect field data, experiments were carried out in selected fields of Urmia Plain in 2015. These tests were carried out in five fall wheat fields, which were all irrigated by the closed-end strip method under the management of the farmers. In this way, one strip was selected as a test strip in each farm and the evaluation parameters were done for the desired strip. In this research, the hydrograph information of the incoming flow, the time of flow interruption, the geometric parameters of the strip, the amount of soil moisture discharge in the root zone, the progress stages, and other characteristics were measured and evaluated. The inflow hydrograph was measured by installing WSC flumes at the beginning of the strips. To measure the advance speed, the strip under test was nailed at 10 m intervals and the advance times were recorded with the movement of the water flow. The cutoff time was applied and recorded according to the opinion of the farmer. The geometric parameters of the strip, including the length, width, and slope of the strip, were obtained by mapping the tested strip. The net depth of irrigation was calculated based on the amount of soil moisture discharge in the root zone by sampling the soil just before irrigation and the gross depth of irrigation was calculated based on the amount of water given.
 
Results and Discussion
The model overestimated in some irrigations and underestimated in others. The maximum efficiency of irrigation application in the second farm (f2) and the third irrigation round (Irrg.3) with a value of 65.51% due to the application of irrigation management to reduce the flow and the minimum efficiency in the fourth farm (f4) and the first irrigation round (Irrg.1) with a value of zero percent due to the heavy rain a few days before irrigation (the soil was completely wet and its net water requirement was zero) and the farmer's re-irrigation, zero efficiency was achieved. Also, the WinSRFR software could not simulate the cut-back method well. The average efficiency in all tested farms was estimated at 23.58%. The reason for this is irrigation with low frequency and high depth of irrigation. Also, the non-uniform leveling and inappropriate slope of the strips can be considered as another factor in reducing the efficiency, which causes the slow movement of water along the strip and the increase of deep penetration losses at the beginning of the strip. The model has been able to correctly predict the progress of water flow in all irrigations. In the second irrigation of the third field, the advance time of the model has more accurately simulated the advance time of the flow compared to other irrigations.
 
Conclusion
According to the results, the simulation of the progress of the water flow and the prediction of the application efficiency by the zero inertia model by WinSRFR software were close to the measured and calculated results; So, it can be said that WinSRFR software can model with ideal accuracy (NRMSE<10%) the closed strip irrigation field under farmer management. The failure to accurately estimate the parameters of the Kostiakov-Lewis infiltration equation and the Manning roughness coefficient, which is different in each irrigation cycle, is the cause of the error between the measured and predicted values. The results of this research showed that in the closed field fields under the management of farmers, excessive watering of the plants by the farmers caused deep infiltration losses from the root zone and the main factor of reducing efficiency in the mentioned fields. Also, the uneven and low slope of the fields, which the farmer is unwilling to level due to the high cost of leveling the land and causing the water to not move well in the strip, can be another reason for the decrease in efficiency in the fields. For accurate evaluation, it is suggested to use volumetric meters to measure the volume of water delivered to farms. Because the fluctuations resulting from the pump during irrigation cause errors in evaluation and modeling. On the other hand, due to the low willingness of farmers to implement irrigation systems under pressure, to reduce water losses, the efficiency of surface irrigation should be increased.