Calibration of Channel Roughness Coefficient for Thiba Main Canal Reach in Mwea Irrigation Scheme, Kenya
Volume 3, Issue 6, November 2015, Pages: 55-65
Received: Aug. 15, 2015;
Accepted: Sep. 11, 2015;
Published: Oct. 15, 2015
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Imbenzi J. Serede, Department of Planning and Design, National Irrigation Board, Nairobi, Kenya
Benedict M. Mutua, Department of Agricultural Engineering, Egerton University, Nakuru, Kenya
James M. Raude, Department of Biomechanical and Environmental Engineering, Jomo Kenyatta University of Agriculture and Technology, Juja, Kenya
Canal roughness is one of the most sensitive parameter in simulation of irrigation canals. The present study attempted to calibrate the channel roughness coefficient (Manning’s “n” value) along the Thiba main canal reach, through simulation of canal discharges and water depths using HEC-RAS Model. After HEC-RAS model was calibrated and validated using two sets of observed discharges and water levels, it was used to simulate the hydraulic behaviour of Thiba main canal reach in Mwea Irrigation Scheme (MIS). The model was used to simulate different flows in the main canal as a result of varying the design discharges through the sluice gates and drop structures. Statistical and graphical techniques were used for model assessment to establish its performance. The results of the study showed that an increase in roughness coefficients caused a corresponding increase in the water levels for both Link Canal II (LCII) and Thiba Main Canal (TMC), while a decrease in roughness coefficients led to a decrease in water levels for both canals. The largest change in simulated water levels was 0.45 and 0.12 m in TMC and LCII respectively. It was concluded from the simulation study that Manning’s “n” value of 0.023 and 0.016 gave best result for LCII and TMC reaches respectively.
Imbenzi J. Serede,
Benedict M. Mutua,
James M. Raude,
Calibration of Channel Roughness Coefficient for Thiba Main Canal Reach in Mwea Irrigation Scheme, Kenya, Hydrology.
Vol. 3, No. 6,
2015, pp. 55-65.
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