Abstract
It is important to understand variations in hydro-meteorological variables to provide crucial information for water resource management and agricultural operation. This study aims to provide comprehensive investigations of hydroclimatic variability in the Bilate watershed for the period 1986 to 2015. Coefficient of variation (CV) and the standardized anomaly index (SAI) were used to assess the variability of rainfall, temperature, and streamflow. Changing point detection, the Mann–Kendell test, and the Sen’s slope estimator were employed to detect shifting points and trends, respectively. Rainfall and streamflow exhibited higher variability in the Bega (dry) and Belg (minor rainy) seasons than in the Kiremt (main rainy) season. Temperature showed an upward shift of 0.91 °C in the early 1990s. Reduction in rainfall (−11%) and streamflow (−42%) were found after changing points around late 1990s and 2000s, respectively. The changing points detected were likely related to the ENSO episodes. The trend test indicated a significant rise in temperature with a faster increase in the minimum temperature (0.06 °C/year) than the maximum temperature (0.02 °C/year). Both annual mean rainfall and streamflow showed significant decreasing trends of 8.32 mm/year and 3.64 mm/year, respectively. With significant increase in temperature and reduction in rainfall, the watershed has been experiencing a decline in streamflow and a shortage of available water. Adaptation measures should be developed by taking the increasing temperature and the declining and erratic nature of rainfall into consideration for water management and agricultural activities.
Highlights
Climate change has been influencing hydroclimatic systems and caused various impacts with different magnitude and frequency of hydrological extremes to water resources management, agricultural activities [1,2,3], and economic development [4]
Our results suggest that the scarcity of available water is getting worse, along with abrupt changes in temperature, rainfall, and streamflow
Annual and seasonal streamflow variability is consistent with the rainfall, which is in line with the results presented in [76,84,85]
Summary
Climate change has been influencing hydroclimatic systems and caused various impacts with different magnitude and frequency of hydrological extremes to water resources management, agricultural activities [1,2,3], and economic development [4]. Millions of people in Africa are affected by droughts and floods due to hydroclimatic variability. Drought impacts to developing countries with low adaptive capacities are often acute in crop failures, hunger, and loss of life and property. Extreme floods in 1988, 1996, and 2006 caused massive loss of life and properties in the country [8]. An overflow from the Bilate River at the end of July 2006 affected 5370 households in the Humbo Woreda [9,10]. This flood damage has been substantial and exceptional in the watershed
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