With the assumption that the water advance and the infiltration opportunity have an exponential relationship, a new equation was derived to estimate the time of water advance along a surface-irrigated field. Using the derived advance equation, a new method was developed for estimating the Kostiakov-Lewis infiltration parameters. The proposed advance equation and Elliot and Walker's advance equation (two-point method) were evaluated using field advance data from seven locations. The evaluation results were based on the dRMS and NSE indices, which showed the superiority of the proposed equation. The advance equations were compared based on their infiltration depth differences and a comparison showed the superiority of the proposed equation. Also, the average values of infiltration depth in the average actual and computed infiltration opportunity time of the advance phase, and the average infiltration opportunity of the total irrigation time, were compared to the average values of actual infiltration depth using the relative error index. Results showed that the proposed method more accurately estimated the average infiltration depth with an average relative error 5.27% for total irrigation time, 1.90% for average computed infiltration opportunity, 1.80% for average actual infiltration opportunity, and 3.86% for infiltrated depth difference in more than 75% of the cases. The proposed equation and the new method for calculating infiltration coefficients can be recommended for practical use.
