Assessing transfer of stream flow data using swat model For ungauged sub basins in megech river catchment, upper Blue nile basin, ethiopia

Abstract

Water resources have an enormous impact on the economic development and environmental protection. Water resource is available in different forms and can be obtained from different sources. However, mostly water resources assessment and management relies on available stream flow measurements. Megech River is one of the tributary of Lake Tana which is the main source of Blue Nile. The main objective of this study is to assess possibility of transferring stream flow data from gauged catchment to ungauged sub basin (from the main river, Megech, to other tributaries found in the catchment) by using SWAT model based on specified criteria. Data used in this study were collected from NMSA and MoWIE. Before using these data, quality of the data was checked carefully and necessary measures have been taken to improve their quality. Then Megech catchment was modeled using SWAT model and calibrated (R2 =0.72 and NSE=0.71) and validated (R2=0.77 and NSE=0.59). Based on soil, land use/cover, and slope criteria, hydrological and physical homogeneity were compared between the main catchment Megech (gauged) and the sub basins (ungauged) in the catchment; and it was found that sub basin 6,8 and 14 are nearly similar to the main catchment (watershed). Then possibility of transferring stream flow from Megech to sub basin 6, 8 and 14 were tested and it were successful. Testing was made by transferring calibrated model parameter values of main river, Megech, to sub basin sub basin 6,8 and 14 and then caring out sensitivity analysis for the sub basin and comparing the results with the original results at the gauging station of Megech and; and it was found that the sensitivity result is the similar. Hence, it is possible to transfer discharge data of the gauging station to the ungauged sub basins 6, 8 and 14. In sub basin 6, 8 and 14 the comparison results of SWAT flow output, empirical flow and its percentage difference were: 1.74807 cms, 0.91687 cms and 47.5498 %, 4.58654 cms, 2.99436 cms and 34.7142 %, 2.83856 cms, 3.08365 cms and -8.6345 % respectively. Therefore, transfer of stream flow from gauged river Megech to ungauged sub basin sub basin 6, 8 and 14 were possible and similar studies can be conducted in other Ethiopian river basins so as to solve the problem of stream flow data shortage at ungauged rivers for water resources project development