ANALYSING EFFECTS OF DROUGHT ON INUNDATION EXTENT AND VEGETATION COVER
DYNAMICS IN THE OKAVANGO DELTA
Abstract
The impacts of global change especially the recent climate-related
extremes such as floods and droughts reveal significant vulnerability
and exposure of freshwater ecosystems and related human systems to
current climate variability. However, the effects of the extreme drought
in the Okavango Delta system are not well understood and documented.
Therefore, the objective of this use case was to apply the products from
Digital Earth Africa namely: the Water Observation from Space (WOfS)
derived from Landsat, vegetation cover baseline derived from Sentinel 2
data; and data from the meteorological agencies such as rainfall and
measured river discharge data to evaluate the effects of drought in the
Okavango Delta wetland system in relation to its upstream areas in
Angola. In particular, we used the 2019 drought as a case study to
assess inundation extent and vegetation cover dynamics with an emphasis
on floodplain and dryland vegetation. Our preliminary results reveal
that the Okavango Delta permanent marshes are resilient to drought,
whereas seasonal floodplains are susceptible to drought. Further, we
discovered that the geospatial location of floodplains has a direct
effect on the timing of desiccation, with the western tributaries that
flow into Lake Ngami and Thamalakane River being the last to dry out due
to drought. In addition, we found that the drought phenomenon in the
Cubango-Okavango River Basin region started earlier than 2019 spanning
over a period of 5 years; with 2018 as the year when the wetland system
reached a minimum threshold for a tipping point triggered by the 2019
drought. In addition, the results contribute to the development of
large-scale drought risk information and products for the Cubango-
Okavango River Basin with a major focus in the Okavango Delta. Further,
this use case provides recent baseline information on the effects of
drought on vegetation cover and river flows in the Okavango Delta system
at a landscape approach, which are essential elements for making
informed science-based decisions on climate risks management and
Sustainable Development Goals (SDGs) by relevant authorities in the
Okavango Delta and the whole of Cubango-Okavango River Basin. In
conclusion, this use case will be upscaled to other transboundary river
basins in the Southern Africa Development Community.