Changes and variability of precipitation and temperature in the Guna Tana watershed, Upper Blue Nile Basin, Ethiopia

Abstract

This paper studied the spatial and temporal variability of the statistical structures of precipitation Guna Tana watershed, Upper Blue Nile, Ethiopia, by analyzing the time series of temperature and precipitation from six weather stations during the period from 1990 to 2016. Inverse distance weight, precipitation concentration index and MK test statics were used to detect annual and seasonal precipitation concentrations and the associated spatial patterns. The results show that precipitation concentration index values were mainly observed in Guna Tana watershed in which about 83.33% and 16.67% were the uniform concentration of precipitation and strong irregularity of precipitation distribution was observed in the kiremt seasons’ rainfall. The demonstration using Mann–Kendall trend test depicted that most parts of Guna Tana watershed are characterized by variability of precipitation and temperature. The results reveal that significant trends in average rainfall were observed (both positive and negative trends). Those significantly decreasing trends of average monsoon rainfall have the highest value of decreasing slope (i.e., − 1.88 mm/year) for Luwaye station and percentage change of − 31.07% in Bega season. Decreasing slopes (− 0.14 °C/year) and percentage change (− 22.79%) were observed in Luwaye station at the average annual minimum temperature and increasing Sen’s slope temperature recorded at 24.64 °C/year and percentage changes at 0.136% in 10% level of significance at Woreta station in average annual minimum temperature.