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Variability and trend analysis of hydro-climatic variables in the stations found in Jemma sub-basin, Upper Blue Nile, Ethiopia

Kidist Gonfa1, Tena Alamirew2, Solomon Gebrehiwot3

1Addis ababa university, Hydrology and water resource management, Ethiopia
2Land and water resource center addis ababa university, Irrigation and water resource management
3Land and water resource center addis ababa university, Forest hydrology


Abstract


A closer investigation of hydro-meteorological variability at a local scale provides a more nuanced detail vital for water resource management at different scales for different uses. The study was done to asses the Hydro-Climatic variability and trend in Jemma sub-basin.This study characterises rainfall and streamflow variability and trend in Jemma subbasin using the non-parametric Mann–Kendal test, Sen's slope estimator, Cofficient of Variation (CV) and Precipitation Concentration Index (PCI). Variability analysis showed that the subbasin had normal to moderate variability in most stations' mean annual and the JJAS (main rainfall season) period. In contrast, all the stations in the MAM season resulted in high rainfall variability. The coefficient of variation (CV) of annual rainfall for the 68% of the stations was low (< 20%) which is a normal variation while, 22% of the stations' rainfall variability were moderate(20-30%), and the remaining 11% stations variability were found to be highly variable (>30%). Moreover, this study revealed a transfer in the rainfall pattern from bimodal to monomodal in the study areas. The overall PCI values were distributed uniformly in the JJAS (main rain) and MAM (short rainy season). Though not statistically significant, streamflow at Bersa was increasing, while at Robit, it was decreasing : however, it was not statistically significant. Rainfall and streamflow have a weak and statistically insignificant relationship. It suggests that the change in streamflow was driven by sources other than rain. As a result, in locations where physiographic characteristics influence the hydro-climate, the variability must be explored basin by basin.


Keywords: Coefficient of variation, Mann Kendall test, precipitation concentration index, rainfall, streamflow


Contact Address: Kidist Gonfa, Addis ababa university, Hydrology and water resource management, Nifas silk lafto sub city kebelle 03, 2003 Addis Abeba, Ethiopia, e-mail: kidiwosen@gmail.com


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