Analysis of Discharge and Efficiency of Irrigation of Primary Canal of Aik Bual Reservoir, Central Lombok Regency

Abstract

This study aimed to evaluate the flow rate and effectiveness of the main canal in the Aik Bual Reservoir as part of the irrigation network supporting agricultural activities. The method used in this study was a quantitative approach with hydraulic analysis using the Manning equation. The data obtained included the canal cross-sectional dimensions, canal bed slope, roughness coefficient, and discharge measurements at upstream and downstream points. This data was then processed to determine the flow capacity and water distribution efficiency. The analysis results indicated that the flow rate calculated using the Manning method was 1.20 m³/s. Meanwhile, field measurements showed a decrease in discharge from upstream to downstream, with the discharge recorded at 0.96 m³/s. This represents a water loss of 0.24 m³/s during the distribution process. These results indicate a canal efficiency of 80%, which is considered good according to irrigation canal efficiency standards, which range from 70% to 90%. Estimated water loss is caused by several factors, such as leaks in the canal walls and bottom, sedimentation that reduces the cross-sectional capacity, and the growth of weeds that obstruct water flow. Furthermore, the physical condition of the canal, which is not yet fully watertight, also affects distribution efficiency