Latest research shows that 64% of wetlands worldwide have been lost since 1900, and that 76% of populations of freshwater
plants and animals have disappeared in the past 40 years alone (according to the 2015 WWF’s Living Planet report).
Drought’s effect on wetlands
As South Africa remains in the grip of a 100-year drought, we look at
the impact this climatic phenomenon will have on our vital wetlands,
the ‘lungs’ of the water catchment system.
By Paul Fairall
For the purpose of this article, we will use
a valley bottom wetland decanting into a
river as an example.
A
drought will severely affect
wetland capacity and plants.
One of the main functions of a
wetland is the storage of water, which
is slowly released into the catchment
system over a period of several years.
This storage ability will be seriously
affected by a drought and the period
of time that it will be able to decant
into a catchment system will decrease
exponentially.
During the storage period in a wetland,
numerous attributes of the water are
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changed, led mostly by the purification
of the water during the period it is stored
in a wetland, including a vast amount of
cleaning and purification of the water
content. This process is facilitated by
numerous wetland plant species as
well as the sequencing of excess heavy
metals, which are removed. The process
is greatly enhanced by the anaerobic
condition of the plants in the system.
With the amount of water released
into a catchment system decreasing,
the water quality will also diminish in
its clarity and quality. Certain impurities
that would have been changed by the
plants will also start declining and the
Water Sewage & Effluent May/June 2018
amount of unpurified water entering
the system will increase.
The functionality of the wetland
will be overall affected as the drought
severity increases, as the amount of
water released will diminish and its
dilution effect to the catchment will
start lessening, affecting the whole
catchment.
As wetland science is less than
seventy years old, not enough research
on a larger scale has been undertaken
to provide an exact amount of all the
effects a drought will have on wetlands
in general. Owing to the fact that up to
90% of the wetland science has been