Changes on Selected Hydrologic Regimes in Southeast Blue Nile River Basin: The Case of Neshe Watershed, Ethiopia

Abstract

Variability of hydrologic regimes is the major indicators of change in the climatic condition of the area. Hence, a good understanding on the changes of hydrologic regime is crucial for sustainable water resources management. However, investigations on such relationships are little in Ethiopia both at national and watershed scale. Therefore, this study was designed to deal with the change in rainfall and stream flow pattern of Neshe watershed for the period of 33 years (1972-2005) in South-East Blue Nile Basin, Ethiopia. The hydrologic data were obtained from Ethiopian Ministry of water resource and National Meteorological agency. Statistical correlation and linear regression analysis was used to detect the periodic trends of the change in the selected hydrologic regimes. Trend analysis for the period 1972 to 1986 has revealed insignificant seasonal variation in the total flow and annual rainfall (p > 0.05). However, dry season base flow and mean annual peak flow were significantly reduced. For the period 1987 to 2005, total flow showed a noticeable increasing trend in the wet season and a decreasing trend in its dry season flow while; base flow in the wet season, annual peak flow and rainfall were not considerably varied. But an imperative dry season decreasing trend was observed on the base flow. Even though, seasonal and periodic variations in terms of increase or decrease for the whole considered hydrologic variables were observed, the overall (1972 to 2005) time series analysis on the hydrologic variable revealed that rainfall and stream flow show a significant increasing trend in rainfall; total flow and peak flow components while a decreasing trend in base flow. Therefore, it is concluded that the study shows the annual variation in water yield potential of Neshe watershed.

Keywords: watershed, hydrology, total flow, peak flow, base flow, rainfall

DOI: 10.7176/JEES/9-2-05