Ingénierie des systèmes d’irrigation et de drainage

Optimization of Canal Cross Section for Minimum Seepage Loss: Increasing Net Benefit from Crop Production (Case Study of Korir Irrigation Scheme Kiltie Awlalo Woreda)

Abstract

Abebe Besha Gutu*

The objective of the research is minimizing the seepage losses from irrigation canals while increasing the benefit from crop production in Eastern zone of Tigray Region Tabia Genfell, Kilite awulalo woreda korir Irrigation Scheme. During the design of canal the cropping pattern selected were pepper, cabbage, potato, tomato and onion for dry season and maize, wheat, teff, barley and pea for wet season. Realizing that the single crop cannot solve the food security and economic status of the farmers, this research was aimed to solve the problem by using the original cropping pattern along with optimization of canal cross-sections to minimize the shortage of discharge and maximize the net benefit. Accordingly, the linear programming (LP) model formulated, under different scenarios to obtain maximum benefit. The model developed under full design (assumption of no losses), existing condition (under measured seepage), under optimum discharge (minimum seepage) and lastly under optimum discharge and new proposed area and their result were compared to each other in terms of area allocation, maximum profit and saved discharge. The objective function of the model is maximization of net benefit and the constraints of the model were minimum area to be irrigated, maximum area under each secondary canal, constraints of seed and fertilizer cost and constraint of optimum discharge in canals. The result of maximum benefit scenario allocates the minimum required area for pepper, cabbage, potato and onion by allocating 62.5ha, which is maximum area for tomato crop. In terms of saving discharge, the existing condition and scenario IV first condition similar with value of 65% however despite of their saved water, the benefit of existing scenario (scenario II first crop pattern) less by 10% than scenario IV 1st crop pattern. The replacement of cabbage with spinach and potato with carrot in scenario IV second crop pattern save 75% of canal discharge but the net benefit reduced by 2,401,350.00 ETB from scenario IV first condition. In terms of saved discharge during optimization of canal cross-section 20%, 68%, 86%, and 69% amounts of discharge saved from Sc-1, Sc-2, Sc-3 and Sc-4 respectively when compared with existing condition.