Abstract
In river basins such as the Olifants, the evapotranspiration has been documented as
the biggest water user and therefore one of the most important hydrological processes in the
basin. Thus, using the Soil and Water Assessment Tool (SWAT) model, this study attempted to
assess the hydrological responses of evapotranspiration (ET) to climate change in the Olifants
River basin over a period of six decades, focusing mainly on the upper catchment (UC) of the
basin. The study showed, on average, a general decline of seasonal ET with a decrease of
10.5% in spring, 29.8% in summer and 17.3% in winter. However, autumn ET showed an
average increase of 12.5%. With (1960 – 1970) decade considered as the baseline, the study
also found that annual ET in the UC, has been on the decline consistently since the 1960s with
the most recent decade (2010 – 2018) taking the biggest share of the drop (12.8%). Here, the
average annual decline of ET of 1.75 mm/yr was observed with most of the decline happening
in the last decade. This general decadal trend of annual ET mortality in the area coincides with
the temperature rise and precipitation decrease of the area, signifying the impact climate
change may have had on the evapotranspiration for the past six decades.