Performance Evaluation And Optimization Plan For Fentale Irrigation Scheme

Abstract

Ethiopia’s economy is mainly dependent on agriculture which contributes more than 50% to GDP, about 60% for foreign exchange earnings, and provides livelihood to more than 85% of the population. Although the country is gifted with ample water resource, the agriculture is based on rainfall. Due to this, the country is not able to feed the citizens. Thus it is essential to develop irrigation schemes and to evaluate the performance of the existing irrigation schemes to increase agricultural productivity. Fentale irrigation scheme is one of the irrigation schemes with a design area of about 18000 ha. But, it does not meet the desired objective, hence the objectives of the study were evaluating the water delivery performance of the scheme and to determine the optimal crop mix pattern that maximizes profit using a linear programming model. Evaluation of the water delivery performance of the scheme was carried out for three months (Feb to April 2020) using four indicators (adequacy, efficiency, dependability, and equity). Climatic data of Metehara station was used to compute the crop water requirement using CROPWAT 8.0 computer program. To know the actual water delivered to the fields, measurements of water from the main canal off takes were carried out using the AA type current meter and floating method. For the optimization plan study, the data like production rate, production cost, and selling price of different crops were collected by interviewing the farmers. The water delivery performance study result showed the performance of the scheme in terms of adequacy (0.94), dependability (CV, 0.1), and equity (CV, 0.06) were good. However, the efficiency (0.73) of the scheme was in the fair range. These values indicate that the water supply of the scheme was good even though the area irrigated during the study period were too small compared to the designed command area. The linear programming model solved by LINGO 17.0 for the case when the area to be irrigated which have completed structure and the water available was the mean discharge which flow in the main canal for the past two years results a net benefit of 852,715,900 birr by allocating 2168, 5000, 623, and 20 ha of land for Maize, Onion, Tomato, and Pepper respectively. And this result depicts that it is possible to irrigate all the areas which have a completed irrigation network with the available water for one irrigation season. The LP model when all the designed areas taken in to consideration and the available water is 174,960,000 m3 for one irrigation season results a maximum net benefit of 1,032,761,000 birr by allocating 11496.77,5000, 623, and 20 ha of land for Maize, Onion, Tomato, and Pepper respectively.