Projections of hydrological changes and riverflow extremes using TerM land surface model in the Limpopo River Basin, South Africa
Abstract
Increasingly frequent hydroclimatic extremes in South Africa necessitate a robust understanding of how changing climate drivers will influence regional water balance. This study evaluates the impacts of climate change on hydrological extremes within the Limpopo River Basin, a region historically vulnerable to catastrophic flooding and prolonged droughts. The INM RAS-MSU (Terrestrial Model; TerM) Land Surface Model was used to project river flow from 2020 to 2100. The atmospheric forcing was derived from the CMIP6 ISIMIP database under the SSP1-2.6 and SSP5-8.5 scenarios. Projections for the near future (2020–2055) and far future (2065–2100) periods were compared against a 1979–2014 baseline, with high-flow events (floods) computed at the 95th percentile. Intra-annual streamflow patterns remain consistent with historical trends but are projected to peak by more than 50%, particularly under the high-emission (SSP5-8.5) scenario. Peak flow increase will likely occur during the austral summer (January-February), while a pronounced decrease is projected during spring (September-November). Despite an increase in pronounced peaks in rainfall, evaporation, and runoff in May, the basin exhibits a statistically insignificant decreasing trend in these variables and annual streamflow between 2020 and 2100. This suggests a shift towards a more volatile regime, with intensified high-flow extremes in January and February punctuated by increasing dry conditions in March and September. Climate change is expected to intensify hydroclimatic extremes in northeastern South Africa, where austral summer rainfall variability is strongly influenced by tropical cyclones, the El Niño–Southern Oscillation (ENSO), and convective rainfall. The findings provide an evidence base for strengthening climate adaptation policies and measures to reduce the impacts of hydroclimatic extremes in northeastern South Africa.