ABSTRACT 

Given the increasing freshwater scarcity, the performance of irrigation is critical in increasing and sustaining agricultural productivity in the water-scarce and largely arid and semi-arid Kenya. Irrigation currently accounts for most of the water withdrawals in the country, and the required improvement in the performance of irrigation is hampered by inadequate benchmarks upon which to base effective planning. This study was conducted between September and October 2008 to analyze the economic efficiency of irrigation water-use in Mwea Irrigation Scheme in the Upper Tana River Basin in Kirinyaga District, Kenya. The objectives of the study were to determine response of rice yields to the quantity of irrigation water used in Mwea Irrigation Scheme, the economic water-use efficiency, and the main factors explaining the efficiency. This required data on quantities of water withdrawn for irrigation, irrigated land area, working capital, labour and rice output, as well as other technical and socio-economic features of the irrigators. Questionnaires and field observations were used to collect secondary data on these variables from a sample of 121 out of the 4,189 rice farms. Descriptive statistics, regression and correlation tools were used for data analysis. The results were presented in form of tables, plates and graphs, from which discussions, conclusions, and recommendations were made. The study revealed that the quantity of irrigation water as was used had positive but insignificant effect on rice output, probably implying over-use of water. Technical, allocative, and overall economic (cost) water-use efficiencies in the Scheme were 69%, 91%, and 63% respectively. Further, technical efficiency was explained mainly by the actual duration of land preparation, water conflicts, drain water re-use, and availability of water in the canal. It is recommended that technical and institutional changes be made in order to improve technical efficiency of water use in the Scheme. Specifically, these include dry land preparation, shortening of land preparation period, cultivation of more water-efficient rice varieties, non-flood weed control, and construction of large-scale water storage infrastructure. Other recommendations are canal lining, installation of water control structures, drain water re-use, capacity-building of IWUAs, and integrated approaches to water management in the Thiba and Nyamindi river basins. This study contributes to effective and efficient decision-making on irrigation planning and management in Mwea Scheme. It will also facilitate the development and implementation of the National Irrigation Policy that is currently being formulated. In addition, it is expected to generate more interest in irrigation research in Kenya to help achieve the national macroeconomic development objectives of poverty alleviation, food security, employment creation, and industrialization.