Land Suitability and Water Availability Evaluation for Surface Irrigation: The Case of Borta River Catchment, Western Oromia

Abstract

Surface irrigation is crucial for enhancing agricultural productivity and food security in Ethiopia. However, optimal utilization of land and water resources is required for sustainable irrigation development. This study evaluated land suitability and water availability for surface irrigation in the Borta River catchment, western Oromia. The methodology combined geospatial analysis using ArcGIS, field soil sampling, and irrigation water requirements estimation through CROPWAT model. The study utilized GIS-based multi-criteria evaluation and weighted overlay analysis to assess the suitability of land considering slope, soil properties, land use/land cover, and proximity to water sources as key parameters. Soil samples from representative pits were tested for pH, electrical conductivity and calcium carbonate content. Results showed that the chemical properties of the soil were not limiting factor for surface irrigation in the catchment, since the test value fell in the range of highly suitable to moderately suitable. The slope classification results showed that 7.1 % of the land is highly to moderately suitable for surface irrigation. Soil texture of the study area was clay and clay loam and revealed as suitable textures. Land cover evaluation revealed 20% of land under crops or agricultural land as highly suitable and a very small portion, accounting for only 0.1% and totaling 12.92 hectares, was identified as unsuitable for surface irrigation development. Regarding water availability, the river had a mean annual flow of 23.8 m3/s, with a minimum flow 4.5 m3/s during the dry season. After 25% released for ecological purpose annual average flow of 17.848 m3/s founded. However, during selected irrigation season (January to May) it is found to be 3.5 m3/s flow were available for irrigation purpose which can irrigate an area of 3587 ha out of suitable areas, this shows irrigation potential of the catchment was about 49.5% of overall suitable command area. Gross irrigation requirements were computed for dominant crops -maize, onion, and potato. Comparative analysis of water demand was (7.0035 m3/s) and Available flow was 3.5 m3/s. The findings clearly indicated that the demand for irrigation water exceeds the available stream flows. To address this water scarcity issue, it is advisable to implement advanced irrigation water management techniques, leverage technology to enhance water use efficiency, construct water harvesting structures, and investigate groundwater sources to fully unlock the identified irrigation potential within the study area. The integrated methodology has offered a comprehensive evaluation of land suitability and the availability of water resources for the planning of surface irrigation. These significant findings will serve as invaluable insights for stakeholders, facilitating sustainable agricultural water management within the Borta River catchment area.