PERFORMANCE EVALUATION OF FIELD WATER APPLICATION AT TENDAHO SUGAR PROJECT, ETHIOPIA

Abstract

Sugarcane is fully irrigated crop in Ethiopia. But, there is little information on the field water application performances of sugar estate farms. Open canals are the main systems for supplying irrigation water in these farms. However, most of these schemes are frequently cri ticized for their low conveyance and field water application efficiencies. Under the water scarce situation, improving the canals conveyance efficiency and field water application can offers an opportunity to realize field level water savings. This study was done a purpose of identifying and understanding the current level of field water application efficiencies of Tendaho sugarcane irrigation scheme using appropriate on field irrigation performance indicators. Primary/direct field data collection and some secondary data were used to undertake planned objectives. Canal conveyance evaluation was done for tertiary canals based priority of dominant conveyance defects observed in the sugar estate. Field water application evaluations were done during the normal irrigation practice of the sugar estate considering: application efficiency, storage efficiency, and deep percolation losses. The relationships between coefficient of uniformity and distribution uniformity have also described based on opportunity time for each quarters using the linear equation. Tertiary conveyance was evaluated by using volume flow measuring method using Parshall flumes set at inlet and outlet of representative canals. From results, the mean conveyance efficiency of tertiary canal was 59.589% with high amount of water losses. From field evaluation, most of field irrigation activities were not carried out on timely schedules. These resulted in overall mean on-field water application efficiency of 56.57%, 70.30% storage efficiency and 91.93% distribution uniformity at target application depth with the overall system efficiency of to 30.81%. Other factors found to affect irrigation efficiency are cut-off time, inflow rates, soil type, and furrow shapes. The results of irrigation scheduling have showed smaller irrigation intervals. To improve irrigation scheduling different net depths of application for each soil has proposed based on soil, crop property and climatic condition of the area. Finally, the inflow rate and cut-off times of two soils are proposed based on field obtained evidences. The inflow rate of 5l/sec and cut-off time of 45minute were recommended as best decision variables to be considered.