Application of GIS based multicriteria evaluation techniques in assessing potential for surface irrigation for paddy-rice cultivation :

Abstract

Irrigation has attained increasing importance the world over because of the growing demand for food by a rapidly growing world population. Uganda depends on the rain fed agriculture with limited use of irrigation for agricultural production. It is estimated that more than 90% of the food supply in the country comes from low productivity rain fed smallholder agriculture and hence rainfall is the single most important determinant of food supply and the country’s economy. This study has focused on assessing the suitability of Surface irrigation for paddy rice cultivation of river Malaba sub-catchment using Geospatial techniques (ArcGIS tools) for analysis to support location decisions with respect to the implementation of Agricultural land planning and management, the study further assesses how the major water source within the catchment can be utilized to provide water for surface irrigation. Suitability assessment for surface irrigation development for paddy rice cultivation was identified by considering the irrigation suitability factors such as slope, soil, land use land cover and rainfall distribution under the multicriteria evaluation using the weighted overlay method. Other methods including CROPWAT were utilized to determine the crop water requirements of paddy rice crop under consideration. This surface irrigation suitability analysis for paddy rice cultivation will be valuable to land managers, agricultural officers and farmers in land-use planning and management. The main aim of the case study was to identify the suitable areas for surface irrigation development for paddy rice cultivation in River Malaba sub-catchment eastern Uganda. The total irrigable land of the sub-catchment is 59.51% (40929.75 ha) under highly suitable, 35.9% (24690.26ha) under moderately suitable for surface irrigation and the rest 3159.29ha (4.59%) is classified as non-suitable (N). The annual average minimum flow of river Malaba is estimated for every month and assessed to determine its capability to meet the gross irrigation water requirements for paddy rice in the growing months with in the season, 36.16037 cumecs are required for the first growing season (April-august) and 55.7587 cumecs are required for the second growing season(September-January). The study was carried out for river Malaba sub-catchment and it is possible to apply the exercise to other sub-catchments in the entire Mpologoma Catchment and possibly the whole country too. Key Words: Surface Irrigation, Paddy rice cultivation, ArcGIS, MCE, AHP, CROPWAT, water availability assessment.