Assessing the field irrigation performance and alternative management options for basin surface irrigation systems through hydrodynamic modeling.

This report assesses the field irrigation performance in terms of application and requirement efficiencies and distribution uniformity, along with the impact of improved management options for basin irrigation systems, based on the use of Surface Irrigation Simulation Software (SIRMOD). For this study, fields have been selected at different farms, which were monitored during the Kharif 1995 and Rabi 1995-1996 irrigation season. The hydrodynamic model, which solves the complete form of the Saint-Venant Equations, has been applied for the irrigation simulations. Further, the hydrodynamic model - as used in SIMOD - is based on the Eularian integration approach. The Newton-Raphson procedure is applied for solving the equations for each computational node, and the Preissmann double-sweep algorithm is applied for solving the banded matrix, which results from the Newton-Raphson procedure. In order to run the hydrodynamic model, the infiltration function (Modified Kostiakov-Lewis Equation) has to be calibrated first. In this study, the volume balance analysis has been applied in order to calibrate the infiltration functions for the selected irrigation events of four sample fields (basins). The hydrodynamic model has proven to be a powerful tool for assessing the field irrigation performance, but, moreover, to develop improved irrigation practice scenarios. Through the simulations, the impact of optimizing has been quantified, which shows that for quite some irrigation events the impact is considerable in terms of water savings. However, for the farmer it is difficult to know how much water to apply in order to meet the exact crop water requirement. Further research is being conducted on basin, as well as bed-and-furrow irrigation systems in order to address feasible operation and management techniques for the farmers in order to improve their field and farm irrigation performance and achieve both water savings and higher crop yields.