Integration of pressurized irrigation suitability maps in estimating current and future irrigation water demand for the Nyamugasani catchment

Abstract

Catchment management plan enables planning toward using water resources effectively and efficiently to achieve long-term sustainable development for the growing water demands with same water resources within the catchment and its associated risks. The development of pressurized irrigation is recommended for its high efficiency. This project was aimed at developing drip and sprinkler irrigation suitability maps and determining the irrigation requirement to adequately plan for future irrigation development water allocation in the Nyamugasani catchment management plan. The parameters used for generating suitability maps were soil texture, slope, distance from streams and land use. Using the Analytical Hierarchy Process criteria weights were assigned to the different parameters to develop suitability maps using QGIS and ArcGIS for drip and sprinkler irrigation using their corresponding irrigation suitability index. A catchment development plan was developed to determine the areas for irrigation development for future years. Using the CROPWAT model irrigation requirement for the different areas was determined using red sandy loam and a cropping pattern adopted from Mobuku irrigation scheme. Annual irrigation requirement was for the years was determined. The farmland was 149 km2 which was 29% of the catchment in 2022. The highly suitable area for sprinkler irrigation was 77 km2 and for drip was 119 km2. The crops considered were maize, cotton, small vegetables, beans and tomatoes. The estimated irrigation requirement for future irrigation development was done for 2022, 2027, 2032, 2037 and 2040. The irrigation requirement for the drip was 148,040.48, 289,483.14, 858,319.41, 1,333,952.57 and 1,746,802.46 cubic metres respectively. For sprinkler, the irrigation requirement was 355.23, 215,170.73, 508,660.14, 1,017,320.29 and 2,086,111.82 cubic metres respectively.