Page 52 - Research & Innovation Report 2020
P. 52
SCIENCE
How day zero could have
been prevented
Catchment management could have prevented the 2020/21 build up to the Day Zero water
crisis in Nelson Mandela Bay and the Kouga Municipality.
“Most of the Eastern Cape’s Nelson Mandela Bay (NMB) Metro “Ecological-economic modelling predicts that removing alien trees
and the adjacent Kouga Municipality will soon run out of water,” and restoring overgrazed land in the catchments would increase
says emeritus professor of ecology, Richard Cowling. water yield and baseflow by 11 and 14 million cubic metres per
annum, respectively, and reduce sediment loads by 22 million
“Two-thirds of the NMB’s water and 85% of Kouga’s water cubic metres per annum,” says Prof Cowling. “The increase in yield
(including all the water needs of the productive irrigation farming alone amounts to 16% of water drawn each year from the dams on
in the Gamtoos Valley) are provided by three dams fed by the water these catchments by NMB.”
courses and wetlands in the 561 000 ha combined catchments of
the Kromme, Kouga and Baviaanskloof rivers. Like most dams in South Africa, the three in the Kromme-Kouga-
Baviaanskloof catchments are dependent on stormflows after
“These dams are near empty and have been so for more than a year. floods to fill them up. It’s been ten years since a dam-filling rainfall
Over half of the catchments are degraded by alien tree invasions, event occurred in this region. Disaster has been averted largely
overgrazing and wetland destruction. This has compromised their through the contribution of small rainfall events and baseflows
ability to provide water, especially during droughts. (the portion of the streamflow that is sustained between rainfall
A concrete capped gabion weir on the Kromme River near Kareedouw. It was built by Working for Wetlands in the early 2000s
under the supervision of the renowned wetland specialist, Japie Buckle. The weir was established to prevent headcut erosion
of the palmiet-dominated wetland upstream. Photo: Japie Buckle
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