Evaluation of land suitability for surface irrigation under changing climate in a tropical setting of Uganda, East Africa

CONTEXT Assessment of land suitability for irrigation under changing climate holds paramount significance given the pronounced reliance on rainfed agriculture in sub-Saharan Africa. OBJECTIVE To investigate land suitability for surface irrigation under changing climate in a tropical setting of Uganda, East Africa and explore implications for irrigation development as well as food security. METHODS The study used a GIS-based multi-criteria evaluation using the Analytical Hierarchy Process that considered seven factors: soil texture, slope, land use/land cover, soil drainage, distance to river, distance to road network and rainfall deficit. Each factor was rasterized, reclassified and standardized to a similar measuring scale, resulting in a numeric range; higher values indicating areas that are more suitable and lower values indicating areas that are less suitable for irrigation. Weighted factors were added using the weighted overlay approach in the ArcGIS environment to create the final irrigation suitability map. Suitability was further assessed under two scenarios; an increase in average temperature of 1.5 °C and 10% increase in annual rainfall for the period from 2041 to 2060 (scenario I) and an increase in average temperature of 4.3 °C and 20% increase in annual rainfall for the period from 2061 to 2080 (scenario II). RESULTS AND CONCLUSIONS Findings reveal that of the entire area of Uganda, 43.7% is currently constrained, 32.4% is moderately suitable, 23.1% is marginally suitable, only 0.9% is highly suitable, and only 0.02% is not suitable for surface irrigation. Highly suitable land is mostly found in the Lake Victoria Crescent whereas land not suitable for surface irrigation is mostly found in the Karamoja zone. Suitability of land for surface irrigation generally decreased with changing climate. Land not suitable for surface irrigation increased to 0.11% and 0.34%, and marginally suitable land increased to 28.4% and 35.8% of the total area, under scenarios I and II respectively. Whereas moderately suitable land decreased to 27.5% and 20.1%, and highly suitable land decreased to 0.29% and 0.046% of the total area, under scenarios I and II respectively. In both scenarios, suitable land for surface irrigation is highest in the South East L. Kyoga Flood Plain and lowest in the Western Mid-Altitude Farmland. The investigation underscores the dynamic nature of irrigation suitability of land, subject to various influencing factors with climate dynamics being a major factor. SIGNIFICANCE The findings emphasize the importance of adopting adaptive strategies and incorporating climate change considerations into irrigation decision-making processes for increased food production.