Investigating physical irrigation pontetial: a case of Pangani River Basin, Tanzania

Pangani River Basin over the past recent years has been characterized by recurrent droughts that have impacted negatively on its food security. Consequently, the income of the community residing in the basin has been affected, also hampered the country’s socio-economic development. Furthermore, the total population of the district falling within the basin has increased rapidly. To cope with the increase in population and to ensure food security in Pangani river basin, both rainfed and irrigated agriculture will need to be intensified. However, irrigated agriculture has higher potential for intensification. In this study the physical irrigation potential for surface irrigation is investigated. Both spatial data and time series data were used in the analysis. The spatial data used are Digital Elevation Model (DEM) 90m *90 and soil data and the time series data such as rainfall data, minimum and maximum air temperature, relative humidity, wind speed and sunshine duration. From the spatial data, layers of depth, texture, drainage and soil were derived. The weights were then assigned to the layers using Analytical Hierarchy Process (AHP). Multi Criteria Evaluation (MCE) technique in ArcGIS environment was then used to derive potential irrigable areas for different crops and the results were validated with the existing irrigation schemes in the basin. Finally, CROPWAT model was used to estimate irrigation water requirements for selected upland crops and flooded rice. The results for potential zones indicate that most of the suitable areas for surface irrigation lie within the existing irrigation schemes in the basin.