A GIS-Based Multi-Criteria Land Suitability Analysis for Surface Irrigation along the Erer Watershed, Eastern Hararghe Zone, Ethiopia
The high dependency on rain-fed and the incessant erratic rainfall during the main growing seasons in Ethiopia pose a huge threat to agricultural production and productivity. Multi-criteria irrigation land suitability analysis and mapping can play an important role not only in sustainable use of scarce resources, but also in overcoming the global problem of water scarcity and crop production caused due to the high degree of rainfall variability and unreliability. The objective of this study was to determine suitable sites for surface irrigation along the Erer Watershed of East Hararghe Zone, Ethiopia. The study employed GIS-based multi criteria land suitability evaluation method considering fifteen factors , namely, soil pH, soil type, soil drainage, soil depth, AWSC, impermeable layer, ECE, CEC, phase, organic carbon, texture classes, obstacle to root, land use /land cover, slope, and distance from the river outlets to find suitable land for surface irrigation. Each factor was standardized to a common measurement scale so that the results represent numeric range giving higher values to more suitable and lower values to less suitable attributes. Using the Weighted Overlay tool, the values of each dataset were weighted and combined to find the most suitable location for irrigation using the ArcGIS environment. The results of the study revealed that about 386,731ha (11.7% of the watershed area) is highly suitable while 140,308 ha (36.3% of the watershed area) is not suitable for surface irrigation. The remaining suitability classes placed within the marginally and moderately suitable categories were about 151,120 ha (39.07%) and 50,223 ha (12.98%) of the watershed area, respectively. The findings drawn from this study can play an indispensable role in boosting irrigable land and crop production in the study area by considering suitable irrigable lands in terms of the fifteen factors described.