Assessment of potential impacts of climate change on water resources in Ngerengere catchment, Tanzania

Abstract

Global climate change has substantial impacts on local and regional hydrological regime. However, the general understanding of how hydrological regime is affected by climate change at catchment scale is limited. In this study, the potential impacts of climate change on water resources in Ngerengere River catchment in Tanzania were assessed. The HBV model was used to undertake water resources assessment for the Ngerengere catchment and subsequently impacts of climate change on the same. Future climate for 2050s (2040–2069) and 2080s (2070–2099) were downscaled using a statistical weather generator (LARS-WG) from outputs of the Global Circulation Model (HadCM3) under SRES A2 scenario.The HBV model was calibrated and validated using observed streamflow data at Mgude gauge station for the baseline period (1971–2000). The Nash-Sutcliffe efficiency (NSE) of 0.7 and 0.6 was attained during calibration and validation respectively. Downscaling results revealed that LARS-WG performed well in generating future rainfall and temperature data series. The results indicated an increase in minimum and maximum temperature of around 0.2–2.6 °C in the 2050s and around 2.7–4.4 °C in the 2080s. Future rainfall is predicted to decrease by 12–37% in April, May, June and July, while rainfall in the remaining months are predicted to increase by 3–58%. The impact assessment on streamflow of the Ngererengere catchment revealed a decline in the mean annual streamflow by 2.1% in 2050s, whereas an increase of up to 58% in mean annual streamflow is predicted in the 2080s.