Effect of Weeds and Sedimentation on the Hydraulic Behaviour of Irrigation Main Canal System at Kano River Project, Nigeria

Abstract

The dynamic equation for gradually varied flow is presented for the impact assessment of weed and sedimentation on the hydraulic behaviour of main canal systems. The study of the hydraulic behaviour of the canal system reveals the various parameters that are performing below expectations with particular emphasis on understanding the interactions between the design and operational performance of the canal and provide indications of needed improvements to enhance irrigation water requirement. The experimental set up consisted of three canal reaches CR1, CR2 and CR3. The effect of weed population and sediment on discharge capacity of the canals was evaluated. Canal reach CR1 recorded a reduction in discharge of 25% of design discharge due to the effect of weed only and a reduction of 47% due to the effect of sediment only. Economic analysis shows that, the 33% design discharge in CR1 commanded 37% of the total land causing a loss of 63% of the total land estimated to represent a loss of crops valued at 1.3 billion naira. The Manning\'s roughness coefficient estimated from the Manning-Strickler formula gives an average value of 0.133 for the West Branch Canal reach under consideration which is about eight times the design value of 0.015. Evaluation of the seepage loss indicates an average value of 0.097 m³/s over the entire 814 m length of canal, which is quite low.

Key words: Hydraulic behaviour, irrigation canal, dynamic equation, gradually varied flow.

Nigerian Journal of Soil Research Vol.5 2004: 1-13