Validation of Selected Roughness Coefficient in a Lined Distributary and its Effect on Water Equality

Abstract

In the present study design value of the roughness coefficient for a lined distributary (Chena distributary district Kasur) was validated and its effect on the water drawing capacity of outlets was assessed. Chena distributary off takes from left bank of Depalpur canal at RD 359020. The total length of the distributary is 25.46 km. More than 50 percent of its length has been lined. In this study reach from 0.00 to 7590, a trapezoidal lined section was used. The total number of outlets feed by distributary were 62, and the first 17 were included in the study. A comparison was made between design and field measurements of the canal and the outlets hydraulic parameters using the (Simulation Irrigation Canal) SIC model. A considerable difference was observed between design and prevailing water surface profile elevations and resultantly water drawing capacity of the outlets. The results showed that the optimal value of the roughness coefficient was 0.02 instead of 0.016, the design value. Due to this variation in roughness coefficient outlets at the head were drawing more than allocated share and tail-enders were deprived of their due share. Therefore, proper design and maintenance are crucial for sustainable operation of an irrigation system.