HYDRAULIC MODELING OF KANGSABATI MAIN CANAL FOR PERFORMANCE ASSESSMENT

Realizing the need for improvements in the operation and management of the main canal system through performance assessment, the MIKE 11 hydraulic model was applied to the Right Bank Main Canal system of the Kangsabati project, West Bengal, India. The canal system has a length of 137 km with a delivery area of about 88,867 ha. The model was calibrated for a 15-day irrigation period during 1997 and validated for one irrigation period each in 1995, 1996, and 1997. The calibrated parameters, which are the global resistance number and gate contraction coefficient, are found to be 50 and 0.63, respectively, whereas local resistance numbers range between 15 and 60. Daily observed and simulated flows are in close agreement for the head and middle reaches during calibration and validation periods. However, at the tail reach some mismatch is found. These results are also supported by the statistical tests. Further, a performance ratio (a ratio of the observed flow rate to the scheduled flow rate) is used as an indicator for assessing the degree of uniformity in flow deliveries along the length of the canal. A sharp decline is seen in the performance ratio along the length of the canal because most of the distributaries of the head and middle reaches have drawn more than their desired shares. The tail reach is more sensitive to discharge deviation at the system source than at the head and middle reaches. The results of the study show that MIKE 11 can be successfully used for a large and complex irrigation system (Right Bank Main Canal) to evaluate its performance in the absence of observed flow data and assist in developing comprehensive irrigation management plans for a cropping season.