Trends and climate change analysis for common climate variables in Gelgel Belese Watershed, Upper Blue Nile Basin, Ethiopia

In this study, modeling of temporal trends for commonly climatic variables for the base line period and future time interval was undertaken for Gelgel Belese watershed in Upper Blue Nile Basin, Ethiopia. The climatic variables data from the period 1998 to 2019 was considered the baseline period and the future climate variables data were downscaled using dynamic downscaling method from the Coordinated Regional Climate Downscaling Experiment over the African Domain for 2020 to 2100. Mann-Kendall's trend test and time series linear model were used to test the temporal trends of climatic variables in the study area. The test result of observed precipitation indicated non-significant trend, while the average annual temperature indicated an increasing trend with the rate changes of 0.0067 degrees C/year and 0.005 degrees C/year in Dangila and Chagni stations, respectively. Whereas, in the same time interval non-significant increasing trend in average annual temperature in Pawi station was common. In line with average annual temperature, evapotranspiration indicated significant increasing trend with the rate change of 0.68 mm/5 year in Dangila station and non-significant increasing trend in Chagni and Pawi stations. Future average annual temperature and annual evapotranspiration imply significant increasing trend, whereas mean annual future precipitation exhibited non-significant decreasing trend in the majority of the RCPs in all stations in the future time interval. This change may be responsible for alterations of the hydrological cycle in the study area. Higher increment of temperature and evapotranspiration and reduction of rainfall in the future over the study watershed may result in decreasing pattern of total flow of the river in the area. Due to this, water demand dissatisfaction for different water users in the study area may become common event. Thus, the designs of different water harvesting infrastructures for different water users should be taken into account in the study area in the future.