Environmental Challenges 7 (2022) 100528 Contents lists available at ScienceDirect Environmental Challenges journal homepage: www.elsevier.com/locate/envc Analysis of rainfall and streamflow trend and variability over Birr River watershed, Abbay basin, Ethiopia Demelash Ademe Malede a,b,∗ , Tena Alamirew Agumassie c , Job Rotich Kosgei d , Nguyen Thi Thuy Linh e , Tesfa Gebrie Andualem f,g a Department of Hydrology and Water Resource Management at Africa Center of Excellence for Water Management, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia b Department of Natural Resources Management, Debre Markos University, P. O. Box 269, Debre Markos, Ethiopia c Water and Land Resource Center, Addis Ababa University, P.O. Box 1176 Addis Ababa, Ethiopia d Civil & Structural Engineering, Moi University, P.O. Box 3900-30100, Eldoret, Kenya e Thuyloi University, 175 Tay Son, Dong Da, Hanoi, Viet Nam f Department of Hydraulic and Water Resources Engineering, Debre Tabor University, Ethiopia g UniSA-STEM, University of South Australia, Adelaide, Australia a r t i c l e i n f o Keywords: Birr River watershed Mann Kendall test Pettitt test Rainfall trend Streamflow trend a b s t r a c t The analysis of rainfall and streamflow trends provides useful information for the effective hydrological variables, water resource planning, and management systems. Trend analysis is important to understanding the performance and features of hydrological and climatic variables over a long timescale. The goal of this study is to identify and analyze existing relationships between rainfall and streamflow trends, as well as to investigate potential drivers of streamflow variability in the Birr River watershed. The Mann Kendall test, Pettitt test, Sen’s slope estimator, and an indicator of hydrological alterations were used to investigate trends, detection of change points, and the linkage of existing rainfall and streamflow at monthly, seasonal, and annual timescales. The result of this study showed that most rainfall gauging stations did not reveal statistically significant changes. On the other hand, streamflow exhibited a statistically significant increasing and decreasing pattern. In all stations, the streamflow trends and change points were found to be inconsistent. The variations in streamflow without significant changes in rainfall suggested that other variables were influencing streamflow. These could be due to the changes in watershed physical elements, such as alterations in the dynamics of Land Use Land Cover (LULC), which are most likely to be responsible for observed changes in the streamflow fluctuations. The finding of this study can be used as a platform for further studies on the effect of watershed dynamics on hydrological flow variability. 1. Introduction Climate change, along with other factors such as Land Use and Land Cover (LULC) alteration activities are considered the primary cause of changes in the characteristics of rainfall and streamflow (Chauluka et al., 2019; Fenta et al., 2017; Gebremicael et al., 2017; Kliment et al., 2011). Rainfall is one of the most important natural resources in the world, which influences both the spatial and temporal trends of streamflow availability (Fentaw et al., 2017; Kliment et al., 2011). The amount and frequency of rainfall changes have a direct impact on streamflow patterns, agricultural and industrial water demand, distribution, and availability of water in the watershed (Chauluka et al., 2019; Orke and ∗ Corresponding author at: Department of Hydrology and Water Resource Management at Africa Center of Excellence for Water Management, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia. E-mail address: demelashade@gmail.com (D.A. Malede). Li, 2021). Rainfall is the most important atmospheric factor that has a direct influence on streamflow patterns (Zhao et al., 2015). Stream- flow is affected by changes in precipitation and other physical proper- ties of the watershed (Cigizoglu et al., 2005). Analyzing and detecting long-term rainfall and streamflow trend is important for understanding the fluctuation of hydrological flow, agricultural operation, future water resource planning, and management, reducing the risk and negative ef- fects associated with incorrectly assuming stationarity in hydrologic de- sign (Alemu and Bawoke, 2020; Arrieta-Castro et al., 2020; Fentaw et al., 2017; Tadese et al., 2019). Many studies have been conducted around the world on the effect of climate change on streamflow fluctuation patterns (Abungba et al., https://doi.org/10.1016/j.envc.2022.100528 Received 14 January 2022; Received in revised form 16 April 2022; Accepted 21 April 2022 2667-0100/© 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)