Seepage Rate Estimation in Irrigation Canals Using Infiltration Equations and Ponding Test Method

Estimating infiltration amount is very important in irrigation canals. In this regard, there are different methods to obtain the infiltration amount. The studies done to estimate the seepage rates in Iran’s irrigation networks are based on the mass balance method. Ponding test is a benchmark method to determine the canal seepage rate. In this method, a specific distance of the canal is isolated and the seepage rate is obtained by measuring the water level reduction in the pond. In this study, the feasibility of using conventional infiltration models; Kostiakov-Luis, Philip, Green-Ampt, and S.C.S has been investigated to estimate the seepage rate based on the ponding test data. Employing the field data of some ponding tests carried out in irrigation network of Australia, it was found that Kostiakov-Luis, with mean absolute relative errors between 2.3% to 7.4%, is the best model to estimate the infiltration rate in the canal. Although the current methods give a constant seepage rate irrespective of the canal flow depth, the outcome of this study indicates that the seepage rate is not a constant value. It depends significantly on the elapsed time, water level, and soil moisture. Also, it was found that the proposed method is less sensitive to the data gathering duration compared to the current methods.