Insights on the irrigation conveyance efficiency of three canal systems for improving agricultural sustainability in Sri Lanka

System conveyance efficiency of the canals is highly important in planning new irrigation development schemes. Enhancing the efficiencies directly influences sustainable agricultural practices. This study, conducted in 2022–2023, assessed conveyance losses in three major irrigation schemes in Sri Lanka: Maduru Oya, Hurulu Wewa, and Minipe Left Bank Canal. The research aimed to quantify current conveyance losses and identify factors influencing efficiency to inform rehabilitation efforts. Field measurements were taken using the float method to determine flow rates at multiple points along selected canals. Conveyance losses were calculated as the percentage difference in flow between measurement points. Results showed significant variations in losses across the three systems: Maduru Oya averaged 27.8% (standard deviation (SD) = 6.03%), Hurulu Wewa 26.5% (SD = 20.4%), and Minipe Left Bank Canal 33.1% (SD = 15.4%) for the D47 canal and 27.7% (SD = 23.7%) for the D32 canal. Factors observed to influence conveyance losses included canal lining condition, soil texture, and topographical features such as elevation differences between drainage and field canals. The study concludes that targeted rehabilitation efforts, particularly increased lining in high-loss areas and improved maintenance in tail-end sections, could substantially improve system efficiency. These findings provide crucial data for irrigation planners and policymakers in Sri Lankan agriculture.