Hydro-climatic Variability and Trend Analysis of Modjo River Watershed, Awash River Basin of Ethiopia

Mitiku Eshetu

doi:10.7176/jees/11-9-04

Abstract

Climate change and variability is expected to trigger changes in temperature and precipitation series. This study aimed at assessing variability and trend of hydro-climatic variables at Modjo River watershed. Long-term climate data of 5 representative stations with in the watershed (1981-2010) and streamflow data of Modjo gauging station (1983 -2010) were used. Rainfall variability was analyzed using Coefficient of variation (CV), Precipitation concentration index (PCI) and Standardized anomaly index (SAI). Climate trends were evaluated using Sen’s slope estimator and Mann–Kendall trend test methods. The study revealed Most of the stations showed low variation in annual rainfall (CV% <20) while the main (Kiremt) and short (Belg) season rainfall exhibited CV ranging from low to high. Both annual and seasonal rainfall showed a non-significant trend at all stations for the past 30 years. However, majority of stations showed an increasing trend in annual daily average temperature ranging from 0.2 to 0.6ºC per decade. Following increases in temperature and the subsequent rise in evapotranspiration, streamflow has shown a high significant declining trend. The temporal decline in streamflow at Modjo watershed could likely affect downstream Koka dam water reserve. Thus, any watershed management strategy that can optimize water conservation for sustainable crop production and option that can improve flow to the reserve is vital. Keywords: Climate change, Climate variability, Hydro-climate, trend, Modjo river watershed DOI: 10.7176/JEES/11-9-04 Publication date: September 30 th 2021

Highlights

Climate is a vital natural resources on the earth which can be seen as the major backbone of all the water resources, and is one of the key variable that affect both the spatial and temporal pattern of water resources (Fentaw et al, 2017)
Similar reports revealed that, in Ethiopia warming has occurred at variable rates but broadly consistent with global and African trends and rainfall has showed both an increasing and decreasing trend in different areas of the country (NMA, 2007)
MATERIALS AND METHODS 2.1 Study Area Description Modjo River watershed having a total area of 1984.96 km2 is situated in the upper Awash River basin of Ethiopia (Figure 1)

Summary

Introduction

Climate is a vital natural resources on the earth which can be seen as the major backbone of all the water resources, and is one of the key variable that affect both the spatial and temporal pattern of water resources (Fentaw et al, 2017). African continent exhibits higher inter-annual and intra-seasonal climate variability(Boko et al, 2007). Ethiopia is one among countries most vulnerable to climate variability and change (Thornton et al, 2006). IPCC has showed that the historical climate record for Africa shows warming about 0.7 0 C, and a decrease in rainfall over large portions of the Sahel (IPCC, 2007). Similar reports revealed that, in Ethiopia warming has occurred at variable rates but broadly consistent with global and African trends and rainfall has showed both an increasing and decreasing trend in different areas of the country (NMA, 2007)

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