De Jager reiterates, “Further research
is required to explore traditional and
new methodologies to improve the
management and supply of water into
the future.”
In this regard, he highlights the
new concept of ‘natural capital’. This
involves using interventions in the
landscape and natural environment to
derive services such as water resources
that will provide sustainable resilience
to stressors such as climate change.
“Strategies such as natural capital
may be more dependable to reduce
vulnerability and increase resilience of
water resources systems, regardless of
what happens to the future climate,” De
Jager concludes. u
Water Sewage & Effluent July/August 2017
39
• Initiate further impact studies
to assess the possible impacts
associated with increased rainfall
runoff and variability.
•
Use the results to initiate
comparative discussions between
relevant climate modellers to
select a ‘credible’ sample from the
31 scenarios, thereby reducing the
range of possible outcomes and risks
on which future planning can be
based.
• Monitor future improvements to
climate modelling and incorporate
into further research if necessary.
• Initiate further studies, using the
same methodology, to determine
potential impacts on all existing and
proposed supply dams.
• Compare predictions from climate
change impact assessments with
measured data.
”Between 75 million and
250 million people are
projected to be exposed
to increased water stress
by 2020 owing to climate
change. “
of dams is unlikely to decrease in the
future, with most scenarios suggesting
an increase.
U n f o r t u n a t e l y, t h e r a n g e o f
future possibilities remains large and
unpredictable. Since each of the 31
modelled scenarios could possibly
occur, definitive conclusions and
recommendations based on these
results are not easy to make. “One
of the most significant conclusions
from this study is that year-on-year
variability could increase, with 24 of
the 31 scenarios analysed suggesting
this trend,” De Jager confirms. The
increased variability will make the future
less predictable, and thereby impose
added risk and vulnerability, the study
cautions.
Based on these observations,
several recommendations emanate from
the study, the most significant of which
are as follows:
Based on the results from the analysis,
most scenarios suggest an increase in
the rainfall of the Mgeni River System.
Between 75 million and 250 million
people are projected to be exposed to
increased water stress by 2020 owing
to climate change. Climate variability
means that Africa is one of the most
vulnerable continents in this regard.
“Clear evidence exists that the
climate is changing globally,” De Jager
stresses. “This will have an amplified
impact on water resources, and
therefore on water security and supply.
It is imperative that water service
providers consider these possible
impacts in their planning, to be able
to sustain water supply at acceptable
levels into the future.”
To assist the water utility in
managing this potential risk, AECOM
leads in a specialist study to develop
practical methodologies to assess the
impact of climate change on water
resource systems. The study was based
on runoff time-series data derived from
the downscaled results of general
circulation models (GCMs).
“We applied these methodologies
to the Mgeni River System, a key water
resource. Based on the results, we
could derive conclusions regarding the
possible impacts of climate change on
water security in the KwaZulu-Natal
region. In turn, we could recommend
adaptation strategies aimed at mitigating
any negative impacts,” De Jager
explains.
He presented the findings of the
study at the eighth meeting of the
International Commission on Large
Dams (ICOLD) at the Sandton Convention
Centre in May 2016. Speaking under
the theme of ‘Climate Change and Its
Influence on Dams’, De Jager presented
a paper entitled ‘The Potential Impact
of Climate Change on the Long-term
Yield of the Mgeni River System’. “It
was very well received by dam design
practitioners and climate change
specialists from across the globe,” De
Jager comments.
The potential impact of a changing
climate on the hydrology and water
security of the four main supply dams
in the Mgeni catchment area — Midmar
Dam and Mooi Transfer, Albert Falls,
and Nagle and Inanda dams — was
assessed using 31 different future
climate scenarios.
Based on the results from the
analysis, most scenarios suggest an
increase in the rainfall of the Mgeni
River System, with a maximum increase
of 21% being possible. This increase is
intensified in the runoff response, with
an anticipated increase of up to 80% for
some scenarios. Furthermore, the yield