Border irrigation performance with distance-based cut-off

Border irrigation is widely practised for winter wheat production on the North China Plain. Winter wheat is mainly irrigated with groundwater as a supplement to insufficient precipitation to maintain high agricultural production. As a result of the increased demands for water, groundwater levels have declined. Therefore, improvements to border irrigation performance and water use efficiency are urgently needed. The objective of this study was to determine the optimal distance at which to cut off inflow under different inflow rate conditions in closed-ended border systems. The experimental treatments included three inflow rates (high, moderate, and low, with average rates of 6.911 s(-1) m(-1), 4.951 s(-1) m(-1), and 2.811 s(-1) m(-1), respectively) and three cut-off ratios (CRs) arranged in three replications at the CAS Ecological Agricultural Experiment Station in Nanpi, Hebei Province, China. The surface irrigation hydraulic simulation model WinSRFR was used to examine the sensitivity of the existing design to a range of bottom slopes, surface roughness values, and inflow rates to demonstrate the robustness of the solutions in terms of their application efficiency and low-quarter distribution uniformity. The results present the optimum CR values for different inflow rate conditions to maximize irrigation performance. The results indicate that irrigation performance above the optimum CR values for high, moderate, and low inflow rates is not very sensitive to bottom slope, and no substantial changes in performance were noted when Manning's roughness coefficient was between 0.04 and 0.09. A set of inflow rate ranges that corresponds to the recommended CRs that could achieve high irrigation performance is presented.