Assessment of localized seasonal precipitation variability in the upper middle catchment of the Olifants River basin

This study used the Soil and Water Assessment Tool (SWAT) model together with regional climate downscaled (RCD) data from the CORDEX (Africa project), to assess the local seasonal precipitation variability in the upper middle catchment (UMC) of the Olifants River basin. The study results, based on two scenarios (RCP4.5 and RCP8.5), showed a wider monthly and seasonal variability of precipitation. The study also indicated a strong decreasing trend of east-to-west direction of spatial precipitation, with most precipitation concentrated in the eastern part of the study area. Within the western part of the UMC, we also noted another decreasing trend of precipitation from south-tonorth with northern areas of the study area receiving the least amount of precipitation. This study has also revealed a considerable general reduction of future seasonal precipitation especially in the mid-term period (2021–2050). The general reduction in future seasonal precipitation, combined with the increasing temperatures in the area, may exacerbate the drought conditions and reduction in streamflow of the main river (Olifants) and its tributaries, consequently having a negative impact on the economic activities in the basin. doi: 10.2166/wcc.2020.187 s://iwaponline.com/jwcc/article-pdf/doi/10.2166/wcc.2020.187/648742/jwc2020187.pdf German K. Nkhonjera (corresponding author) Megersa O. Dinka School of Civil Engineering and Built Environment, Civil Engineering Department, University of Johannesburg, P.O. Box 524, Auckland Park, 2006, South Africa E-mail: germann@uj.ac.za Yali E. Woyessa Department of Civil Engineering, Central University of Technology, Free State, South Africa