DAM BASED WATER RESOURCES MANAGEMENT PLANNING FOR MAKUTUPORA BASIN IN TANZANIA

Abstract

Across the globe, the scarcity of water poses a significant challenge to human life, particularly in areas with semi-arid climates affecting the domestic, industrial and agricultural activities. In such water scarcity prone areas, better water resources planning is needed through integrated water resources management. The Makutupora catchment located in Tanzania is one such water scarce region in Africa. In this region, water needs are mostly met through groundwater extraction. However, the present infrastructure can only meet around 50% of its current water demand. This deficit can be addressed by tapping the surface water resources of the region by constructing suitable dams for managing the regional water resources. For construction of dams, proper water resource management planning is crucial to ascertain the optimal location and geometrical characteristics of the proposed dam sites. Thus, a dam focussed water resources management planning exercise has been performed here for this basin. The dam location is ascertained using a Multi Criteria Decision Making (MCDM) based framework. The MCDM incorporates different hydrological and logistical criteria to ascertain optimal dam site(s). Here, Analytical Hierarchy Process (AHP) method is employed for performing MCDM analysis. AHP yields a raster that is generated by taking a weighted sum of the criteria considered in this study. Here, six criteria - Stream density, rainfall, land use land cover, geological layer, soil types and slope are selected based on the literature review. Thematic layers corresponding to these criteria are generated using Google Earth Engine (GEE) and QGIS followed by the implementation of AHP, resulting in a dam site suitability raster. This raster elucidates the relative suitability for dam construction and two suitable locations are derived from this map. Furthermore, the raster is classified into four discrete categories viz 1) low 2) moderate 3) high 4) very high suitability. The north-eastern tracts of the basin exhibit the highest suitability occupying around 0.4% of total area, northeast is high suitable (14.8 % of total area), of the north-east and southwest has moderate suitability (74.3 %) and rest (10.4%) is covered by low suitability for the dam site. Different heights of dam and their corresponding inundated area are determined based on topography of the region. The profile of proposed dam containing cross-sections and characteristics of dam such as height, width, and volume are then computed. The planned dam site 1 (situated in northeast part) is categorised as an intermediate dam by the Indian Standards for dam classification. This proposed dam with a height of 7 m, an inundation area of 6 km2 have storage capacity of 25.2 MCM. The results of this study are of direct use for planning better water resources management in water scarce area in general, and the Makutupora basin in particular.