PERFORMANCE EVALUATION OF IRRIGATION SYSTEM AT SECONDARY CANAL LEVEL

Abstract

Performance of irrigation system, in terms of reliable supply and equity in water distribution at secondary canals has been assessed in this study. Mirpurkhas subdivision in Jamrao canal command within Nara Canal Area Water Board was selected for the study. All the 11 head regulators of distributaries and minors were calibrated and new equations for discharge were developed for respective head regulators. By using these equations discharges were measured at head regulators of offtaking irrigation channels for two years i.e. 2010-11 and 2011-12. Study revealed that the reliability of water supply at the heads of secondary canals in the Jamrao canal command is very poor. The analysis on canal operation indicates that 70% of delivery performance ratio (DPR) values fall under poor performance categories. Only 33% reliable supply was released to distributaries and minors. On the average, variation in discharges was very high i.e. 33% in Kharif and between 50% and 57% in Rabi. While, the degree of equity in water distribution among secondary canals was very poor. The most favored canals received 50% to 150% greater discharge of their designed share as compared to least favored canals, whereas, the least favored canals received between 50% and 90% of their designed share. The study suggests that there is a serious need to improve the system’s performance and water supplying agency must pay attention to provide designed share to each distributary and minor.

Keywords

• Discharge
• delivery performance ratio
• design share
• equity
• reliability