Abstract
This study aims to assess the potential impacts of climate change on hydrometeorological variables and drought characteristics in the Ethiopian Bilate watershed. Climate projections under two Representative Concentration Pathways (RCP4.5 and RCP8.5) were obtained from the Coordinated Regional Downscaling Experiment (CORDEX) Africa for the near future (2021–2050) and far future (2071–2100) periods. The Soil and Water Assessment Tool (SWAT) model was applied to assess changes in watershed hydrology with the CORDEX-Africa data. The Standardized Precipitation Index (SPI), Streamflow Drought Index (SDI), and Reconnaissance Drought Index (RDI) were calculated to identify the characteristics of meteorological, hydrological, and agricultural droughts, respectively. Due to a significant rise in temperature, evapotranspiration will increase by up to 16.8% by the end of the 21st century. Under the RCP8.5 scenario, the annual average rainfall is estimated to decrease by 38.3% in the far future period, inducing a reduction of streamflow of up to 37.5%. Projections in reduced diurnal temperature range might benefit crop growth but suggest elevated heat stress. Probabilities of drought occurrence are expected to be doubled in the far future period, with increased intensities for all three types of droughts. These projected impacts will exacerbate water scarcity and threaten food securities in the study area. The study findings provide forward-looking quantitative information for water management authorities and decision-makers to develop adaptive measures to cope with the changing climate.
Highlights
Climate change is associated with shifts in average climatic conditions and extreme events likely to impact human and ecological systems [1]
The results showed the curve number (CN2), soil evaporation compensation factor (ESCO), maximum canopy storage (CANMAX), threshold depth of water in the shallow aquifer required for return flow to occur (GWQMN), deep aquifer percolation fraction (RCHRG_DP), groundwater recession factor (ALPHA_BF), plant evaporation compensation factor (EPCO), and average slope steepness (HRU_SLP) to be the most sensitive parameters
To investigate the implications of the uneven warming rate between the minimum and maximum temperatures, we further examined the Diurnal temperature range (DTR) in the Bilate watershed using the means of the five global climate models (GCMs) for the baseline and future periods, as shown in December, with the tipping point being in October
Summary
Climate change is associated with shifts in average climatic conditions and extreme events likely to impact human and ecological systems [1]. According to the Intergovernmental Panel on Climate Change report (IPCC), the frequency and intensity of heavy precipitation events and daily temperature extremes are expected to increase in the mid-21st century [2]. The increase in long-term temperature and variability in precipitation in different parts of the world and their impacts on the environment are becoming evident. A decreasing trend of differences between the maximum and minimum temperatures was observed for 1979–2004 in Kenya and Tanzania due to a substantial rise in the minimum temperature faster than the maximum temperature [4]. Rainfall variability and trends studies over the African continent during
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