In the recent years, interest in hydrokinetic technology has grown extensively. Hydrokinetic energy conversion stands out as a promising technology for producing the clean energy from moving water in rivers, channels or ocean currents. The Savonius water turbine is the vertical axis turbine which is well suited for low-speed channels and rivers. This paper aims to investigate the flow field and performance of a small scale Savonius water turbine at a low water velocity of 0.5 m/s. In the present study, a two blade Savonius water turbine having aspect ratio of 1.58 was designed and modelled along with model of an open channel. Realizable k-ε turbulence model has been used to carry out Numerical study. Based on numerical study, flow distributions around the rotor has been analysed and discussed. Experimental setup was also designed and fabricated to validate the numerical results. Further, it has been found that Savonius water turbine produces a maximum value of the power coefficient (=0.23) at TSR value of 0.7 in CFD investigation which is in good agreement with experimental results.