Assessing the Impacts of Land Use-Cover Change on Hydrology of Melka Kuntrie Subbasin in Ethiopia, Using a Conceptual Hydrological Model

Abstract

The growth of population and its effect on the land use-cover change have been influencing the hydrology of the sub basin by changing the magnitude of stream flow and groundwater flow. In this paper, the likely land use-cover change impacts on hydrology of the Melka Kuntrie sub basin in the Upper Awash River Basin have been evaluated using the semi-distributed HBV hydrological model and Landsat imageries for two different periods. ArcGIS was used to generate the land use-cover maps from Landsat 5 TM and 7 ETM+ acquired, in the year 1986 and 2003, respectively. The land use-cover maps were generated using the Maximum Likelihood Algorithm of Supervised Classification. The accuracy of the classified maps was assessed using contingency matrix. The result of this analysis showed that the cultivated land has expanded from 1986 to 2003. The land use in 2003, which was mostly converted to agriculture land from forest, grass, or shrub land, showed an increased stream flow in the main rainy season, while the stream flow in dry or small rainy season indicted inconsistency from month to month. In the same time, there was a decrease in evapotranspiration in 2003 land use. The stream flow increased by the 2003 land use was 25% in June, 4% in July, 6% in August and 9% in September that corresponded to 0.065 mm/day in June, 0.077 mm/day in July, 0.07 mm/day in August and 0.039 mm/day in September for the main rainy season as compared to the 1986 land use. The model calibration was carried out using observed hydrometeorological data from 1991 to 2004 and the validation period was from 2005 to 2008. The performance of the HBV model for both calibration and validation was reasonable well and the Nash-Sutcliffe efficiency was 0.86 and 0.78 for calibration and validation, respectively.