Improved volume balance using upstream flow depth for advance time estimation

Modification of classical volume balance models is one of the effective strategies to improving design of surface irrigation and optimal usage of water resources in agricultural section. In this paper, a modified volume balance model is developed to predict the advance curve in surface irrigation based on the variable actual depth at the upstream end of furrow. The simulations of the suggested structure are generated through a combination of different values of the furrow irrigation variables (inflow discharge, length of furrow, and infiltration parameters), to compare between different models and measured data. The results show that the modified volume balance is more accurate than previous equations by model efficiency of 0.94, 0.98, and 0.97 for furrow length of 60, 80, and 100 m, respectively. Sensitivity analysis is made by changing only one input parameter including discharge, field slope, roughness coefficient and infiltration parameters at a time while keeping all others fixed. Furthermore, the inflow rate can have a considerable impact on the model estimations. Nevertheless, the developed model is more sensitive to decreasing inflow discharge amount than to increasing it.