Streamflow is widely utilized in flood and drought studies, water resource management, and planning. It was assumed constant in the past century however, might no longer be valid due to the consequences of changes in land use land cover, climate, and structural design. The objective of this study is to identify and model streamflow changes in Abbay basin. The characteristics of the mean, maximum and 7-day average minimum flow series were investigated, and the statistical Mann–Kendall and Pettitt tests have been used to assess trends and change points respectively. The HBV-Light model was calibrated and validated for twelve years (2002-2013), 1 year warming up period (1 st Jan, 2002 -31 st Dec, 2002), 7 years for calibration (2003-2009) and 4 years for validation (2010-2013). It was observed that in August, 86.21% of the stations had the highest mean monthly flows, while the remaining 13.79% of stations in September. The extreme observed annual mean, maximum and 7-day average streamflow (m 3 ) at Abbay at Kessie station was (576.85, 3696.58, and 79.25) respectively. Kessie watershed was chosen for modeling because of the significant value of trend and change point in all flow series, in addition to the broad area of coverage. The calibration and validation, the performance of the model for land use land cover 2002 was 0.889 and 0.78, and for 2013 it was 0.82 and 0.766 respectively. The overall mean streamflow for the Kessie watershed was 384.57mm/year for land use land cover of 2002 and 397.05mm/year for 2013. Generally there is an increase in streamflow from land use land cover 2002 to 2013 by 141.69mm/year due to the change in land use. The result of the hydrological model is compatible to the Mann-kendall test result. This study indicates that to know the streamflow change in the basin, it is necessary to locate gauging stations for major rivers lacking stream measuring stations in the appropriate locations; develop the stage -discharge relationship early; and build a database that are relevant to each task in the basin. Keywords: HBV, Kessie watershed, Streamflow