Analysis of rainfall and streamflow trend and variability over Birr River watershed, Abbay basin, Ethiopia

•Rainfall and streamflow trends, variabilities and change point detections analyzed.•Nonparametric tests were used to investigate rainfall and streamflow variables.•Most rainfall gauging stations did not reveal statistically significant changes.•Streamflow exhibited inconsistent increasing and decreasing pattern.•The correlation between rainfall and streamflow showed small to medium relationship.