Exploring dynamics of evapotranspiration in selected land cover classes in a sub-humid grassland: A case study in quaternary catchment S50E, South Africa

Land cover change is a pervasive force and it influences the relationship between precipitation (P) and actual evapotranspiration (AET). The study sought to determine variations in catchment scale AET attributable to land cover change over a grassland in the Eastern Cape, South Africa. Remotely sensed rainfall and AET data were used. Land cover maps for the study area were used to extract annual AET from the MOD16 ET product. The method of cumulative residuals was applied to link dynamics in AET with land cover change to enable the application of an appropriate map for retrieving AET. Rainfall and AET were subjected to the Mann- Kendall and Pettitt's tests. Grassland and built-up cover classes AET showed step changes (p < 0.05) indicating sudden changes. Forest cover revealed a marginal trend (p < 0.1), since forest cover change was a slow process. Changes in the evaporative index suggest that land cover influenced AET and this was confirmed by dynamics in the catchment parameter (w). Average w (1.88) indicated that the catchment had a low water retention capacity and this suggests that the hydrological response was sensitive to land cover change. Management interventions are required to improve water retention in the catchment.