Investigating the Effect of Climate Change on the Stream Flows Using Swat Model: the Case Study of Ruvu Sub-Catchment

The SWAT model was applied in the Ruvu River catchment, to simulate the stream flow and to investigate the effect of climate change on the streamflow. The Ruvu RiverCatchment is sub-catchment of a Wami/Ruvu basin, which drains an area of 19, 190 km the main sources of water supply to Dar es salaam City. The observed and simulated flow from IH8 was used for calibrating the model. Sensitivity analysis results showed that from 27 parameters, only 19 parameters revealed meaningful effects on the flow simulation. Calibration was carried out manually and by using optimization tool SUFI-2 from 1966 to 1969, Validation from 1971 to 1972. The calibration and validation on daily basis gave satisfactory results with (R2 =0.75, NSE=0.64), (R2=0.55, NSE=0.52) respectively.The calibrated model was used to simulate the effect of climate change on stream flow. The future climate change data from HadCM2 model were used. The periods used simulation were 2010—2039 (2020s) and 2040—2069 (2050s). The climate variables considered are precipitation and temperature. The future data scenarios indicate a significant increasing in both maximum and minimum temperature values range from0.5 to 1 degree for 2040-2069(2050s) with no change in precipitation, and for period 2010-2039 (2020s) show no change both in precipitation and temperature. The simulation of the effect of climate change indicates an overall decreasing in annual streamflow in the Ruvu River, in the future with the maximum 21% decrease in the annual stream flow