Assessment and analysis of morphometric characteristics of Lake Tana sub-basin, Upper Blue Nile Basin, Ethiopia

Abstract

ABSTRACT This study aimed at assessing and quantitatively analysing morphometric parameters of the Lake Tana Sub-basin and its catchments using remote sensing data and Geographic Information System (GIS). The extraction of drainage network was performed from Shuttle Radar Topographic Mission (SRTM) 30 m × 30 m Digital Elevation Model (DEM) data using the Arc Hydro extension within ArcGIS 10.2. The drainage network analysis of the sub-basin revealed that the sub-basin is a seventh order with a dendritic drainage pattern and very fine drainage texture. Further, the analysis of the study showed that the catchments Gilgel Abay, Ribb and Gumera are a fifth-order stream whereas Megech is a sixth-order stream. Values of bifurcation ratio is high that indicates the presence of a higher number of streams even in the higher orders, high structural disturbance, availability of erodible soils and occurrence of high overland flow and discharge. The drainage density also revealed the basin area is permeable, with high precipitation, infiltration rate and vegetation covers. Moreover, the elongation ratio showed the basin is elongated and low class. The smaller stream frequency indicates that the basin experienced low relief, permeable bedrock and the presence of alluvial fans and flood plains. The results of this study provide information on drainage morphometry for researchers and watershed managers to understand the watershed characteristics. It serves as a basis for improved planning, management and decision making to ensure sustainable use of the basin resources, river basin evaluation, watershed prioritization for soil and water conservation and natural resources management at macro and micro level.