Surge irrigation modeling and scenario analyses for the best furrow irrigation management practices

Abstract

Furrow irrigation with surge flow is a management strategy to improve irrigation performance compared to furrow irrigation with continuous flow. Successful management of surge irrigation corresponds to accurate field practices that depend on different flow hydraulic parameters that make it complex in practice. However, because of this complexity, very few surge infiltration models have been developed. So far, no study has been done to evaluate infiltration equations subject to different surge irrigation modelling concepts under field surge irrigation scenarios. This study investigates two surge infiltration equations of Modified Kostiakov-Lewies (MKL) and Branch Function (BF) using WinSRFR that is the only modelling tool to simulate surge irrigation by using two surge infiltration modelling concepts of Blair-Smerdon (BS) and Izuno-Podmore (IP). Field data were collected on different combinations of two furrow lengths (70 m and 90 m; open-end furrows), two inflow rates (0.4 l s−1 and 0.6 l s−1), and two cycle ratios (0.5 and 0.33). Field measurements confirmed that switching from continuous to surge irrigation significantly improved irrigation performance. Evaluation of the surge infiltration modeling concepts showed that IP had higher accuracy in simulating irrigation performance compared to BS. The MKL(IP) and BF(IP) had the highest accuracy in the simulation of advance time, infiltrated water depth, and runoff. Further analyses showed that decreasing the cycle ratio from 0.5 to 0.33 improved simulation accuracy in advance time, runoff, and irrigation performance, but it reduced the accuracy of simulated infiltrated water depth. Increasing the inflow rate from 0.4 l s−1 to 0.6 l s−1 decreased the accuracy of irrigation performance. However, field observations were only under a limited number of furrow lengths and inflow rates that might not be the best management field practices to increase irrigation performance. Scenario analyses were done to simulate irrigation performance under a combination of possible irrigation managements. The optimal irrigation scenario consisted of adjusting the different inflow rate (0.5–1.2 l s−1), furrow length (100–300 m), cutoff time (360–600 min), and on-time (20–60 min). Results show that using cutoff 360 min and on-time 60 min led to reducing deep percolation and runoff and increasing the distribution uniformity. Based on the scenario analyses for the most efficient irrigation performance in terms of irrigation efficiencies and water losses (runoff and deep percolation), the best irrigation management could be attributed to the furrow length of 200 m that occurs for on-time of 60 min, with a cutoff time of 360 min, and an inflow rate of 0.7 l s−1 although Zreq = 50 mm is not fully irrigated over the whole furrow. Under this scenario, 35 % of the furrow is under deficit irrigation. Scenario analyses showed that we may propose a new surge irrigation management named as “wet-cycle surge irrigation” such that the first surge completes the whole furrow length, and then the subsequent surges will run on wet soil.