evaluation of evalue model to estimate the manning roughness coefficient in furrow irrigation

the manning roughness coefficient is an important parameter in the design and evaluation of furrow irrigation. despite its importance, estimation of this parameter for surface irrigation is very difficult, particularly in furrow irrigation. in this study, an evalue model was used to estimate the manning roughness coefficient in furrow irrigation. the model was based on volume balance and developed to estimate the manning roughness coefficient in surface irrigation. evalue also estimates both infiltration parameters of the modified kostiakov branch function. the main input for evalue is depth of flow along the furrow at different times. evaluation of this model was carried out by comparing simulated advance and resection phases using sirmod software based on the estimated parameters and the measured data. the estimated values of the manning roughness coefficient ranged from 0.02 to 0.102. this model was able to simulate the resection phase, which was more sensitive to the manning roughness coefficient, closely.