Detection of trends in hydrological extremes for Ethiopian watersheds, 1975–2010
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This study investigates trends in streamflow variables for 57 gauging stations distributed across the Ethiopian highlands for the period 1975–2010. We used the Mann-Kendall’s test to detect trends and the Sen’s slope estimator to calculate trend magnitudes. The findings show that more than 70% out of 513 test cases have shown increasing signals, and 32% of the tests were globally field significant at 0.05 level. Increasing change in low-flow magnitudes and decreasing change in low-flow frequency that exceeded 80 percentile (Qmin80p) were more prevalent than the others. Global field significant increasing changes were observed for 40% out of 228 test cases for low-flow amounts, while Qmin80p has shown decreasing trend at 46 out of 57 stations, and 26 of these were statistically significant. The general tendency is towards upward change, but there were some stations that showed field significant decreasing trends for high-flow indicators. General trend signals (upward or downward) and stations with significant changes did not show any spatial pattern. There were even adjacent gauging stations within the same river basin or adjacent river basins that showed statistically significant opposite trends for some test cases. The complex spatial pattern of trend signals is partly attributable to the very complex topographic, climatic, and land cover variations in the country that are well documented in previous studies. Also, the observed trends are difficult to fully explain in terms of climate change or land cover conversion. Generally, the results of this study contradict with previous studies that reported no significant trends in streamflow variables over Ethiopia. The study has important implications for climate change adaptation planning, water-related disaster risk management, and water sector development activities in the country.
KeywordsStreamflow Extreme flows Trend detection Ethiopian watersheds
We are very grateful to the Ethiopian Ministry of Water, Irrigation and Energy (MoWIE) for providing us with the daily streamflow data used for the study.
The first author received financial assistance provided by the International Foundation for Science (IFS, agreement no. W/5103-2) and African Climate Change Fellowship Program (ACCFP).
- Awulachew SB, Yilma AD, Loulseged M, Loiskandl W, Ayana M, Alamirew T (2007) Water resources and irrigation development in Ethiopia. Colombo, Sri Lanka: International Water Management Institute. 78p. Working Paper, pp 1–123Google Scholar
- Berehanu B, Seleshi Y, Assefa MM (2014). Surface Water and Groundwater Resources of Ethiopia: Potentials and Challenges of Water Resources Development. In: Nile River Basin: Ecohydrological Challenges, Climate Change and Hydropolitics.Springer, Switzerland, pp97–119Google Scholar
- Conway D (2000) The climate and hydrology of the Upper Blue Nile River. Geogr J 166:49–62. https://doi.org/10.1111/j.1475-4959.2000.tb00006.x CrossRefGoogle Scholar
- ECE (Economic Commission for Europe) (2009) Guidance on water and adaptation to climate change. Economic Commission for Europe Convention on the Protection and Use of Transboundary Watercourses and International Lakes, United Nation Publication, ISBN: 978-92-1-117010-8, New York and GenevaGoogle Scholar
- FDRE (Federal Democratic Republic of Ethiopia) (2011) Ethiopia’s climate-resilient green economy: Green economy strategy. Addis AbabaGoogle Scholar
- Jiménez Cisneros BE, Oki T, Arnell NW, Benito G, Cogley JG, Döll P, Jiang T, Mwakalila SS (2014) Freshwater resources. In: Kundzewicz Z (ed) Climate change 2014: impacts, adaptation, and vulnerability. Part a: global and sectoral aspects. Contribution of working group II to the fifth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge, pp 229–269Google Scholar
- Kundzewicz ZW, Mata LJ, Arnell NW, Döll P, Kabat P, Jiménez B, Miller KA, Oki T, Sen Z, Shiklomanov IA (2007) In: Parry ML, Canziani OF, Palutikof JP, van der Linden PJ, Hanson CE (eds) Freshwater resources and their management. Climate change 2007: impacts, adaptation and vulnerability. Contribution of working group II to the fourth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge, pp 173–210Google Scholar
- MoWIE (Ministry of Water, Irrigation and Energy) (2014) Ethiopia’s climate-resilient green economy climate resilience strategy: water and energy. Addis Ababa. http://www.greengrowthknowledge.org/sites/default/files/downloads/resource/Ethiopia_Climate_Resilient_Green_Economy_Water_Energy.pdf. Accessed 25 June 2014
- Salmi T, Määttä A, Anttila P, Ruoho-Airola T, Amnell T (2002) Detecting trends of annual values of atmospheric pollutants by the Mann-Kendall test and Sen’s slope estimates—the excel template application MAKESENS. Publication on Air Quality No 31, Finnish Meteorological Institute, Air Quality Research, Helsinki, Finland. http://www.fmi.fi/organization/contacts_25. html. Accessed 12 Sep 2015
- WMO (World Meteorological Organization) (2008) Manual on low flow estimation and prediction: operational hydrology report no. 50. Geneva: WMO-No. 1029Google Scholar
- World Bank (2006) Ethiopia: managing water resources to maximize sustainable growth. World Bank, DC 20433, Washington D.CGoogle Scholar