Hydroclimatic Variability in the Bilate Watershed, Ethiopia

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.

Impact of Climate Change on Hydrometeorology and Droughts in the Bilate Watershed, Ethiopia

“…Since the Belg is one of the crop growing seasons in this watershed [6], an expected The study findings suggest that climate change impacts on drought occurrence in the Bilate watershed will exacerbate water scarcity in the future. Previous studies confirmed that the watershed is highly susceptible to hydro climatological variability [6] with frequent drought occurrences [125].…”

“…Since the Belg is one of the crop growing seasons in this watershed [6], an expected The study findings suggest that climate change impacts on drought occurrence in the Bilate watershed will exacerbate water scarcity in the future. Previous studies confirmed that the watershed is highly susceptible to hydro climatological variability [6] with frequent drought occurrences [125]. We also understand that these droughts will have a longer duration than the baseline period due to climate change.…”

“…Effects of climate change on these variables may induce water scarcity, affect the length of the growing period, crop development, crop evaporation, and the amount of irrigation water, and reduce crop yield [109,110]. It could also result in extreme droughts and loss of live stocks [6].…”

“…Since the Belg is one of the crop growing seasons in this watershed [6], an expected increase in the intensity of droughts might affect the crop growing period. Impacts of drought in the Belg season are more challenging than during the Kiremt due to water shortages in dry seasons often inducing devastating effects to the society [98].…”

“…On the other hand, rainfall variability and trends studies over the African continent during 1983-2020 designated statistically significant increases in the northern and central regions and no significant change in Africa's southern and eastern areas [5]. A recent study in the Bilate watershed also reported a considerable rise in temperature with a faster-increasing rate in the minimum temperature than the maximum and a significant decrease in rainfall and streamflow [6,7].…”