Surface irrigation is one of the oldest methods of irrigation. A key challenge in surface irrigation is the non-uniform infiltration opportunity along the field, resulting in an un uniformity of moisture distribution beneath the soil surface, which reduces irrigation efficiency. Improved irrigation design can enhance both efficiency and uniformity. In this study, a mathematical model is presented to determine the uniformity coefficient for furrow irrigation. Based on this model, furrow irrigation can be designed to achieve maximum uniformity. The proposed model defines the uniformity coefficient as a function of flow rate, length, slope, roughness coefficient, and infiltration parameters, which are combined into three dimensionless parameters. The model was developed by solving the Saint-Venant equations numerically using MATLAB for various furrow configurations. Subsequently, infiltration depths along the furrow and the uniformity coefficient were calculated. A nonlinear model was fitted to the data, enabling the uniformity coefficient to be determined for both the eva‎luation and design of furrow irrigation. To validate the model, experimental data from field measurements were utilized. The uniformity coefficients were measured for each field, calculated using the nonlinear model, and compared. The average error across fields was 4%, demonstrating the high accuracy of the model. Sensitivity analysis revealed that the uniformity coefficient is most sensitive to the following factors, in order: final infiltration rate, required infiltration opportunity time, net irrigation demand, infiltration equation power, furrow slope, furrow length, furrow width, inflow rate, irrigation duration, infiltration equation coefficient, and Manning’s roughness coefficient.

محمد شايان نژاد

محمد مهدي متين زاده , محمدعلي حاج عباسي جورتاني