Water, Sewage & Effluent September October 2018 | Page 11

Water Sewage & Effluent September/October 2018
9
innovations
So, forests and furs, iron ore and
hydropower funded the development
of the infrastructure that makes
Stockholm such a pleasant city today.
The Swedes were also helped by
emigration. In the 19th century, almost
one fifth of the Swedish population,
unable to make a living in their harsh
countryside, left for the US and
elsewhere to seek a better life.
Of course, the exploitation of nature
comes with costs as well as benefits,
although these are often conveniently
forgotten. This continues to be the
mix of people and industries on
the stinking mudflats, making it a
focus for diseases such as cholera.
A combination of wealth and hard
work made it possible to clean up
the river and build the infrastructure
of drainage and water treatment,
bridges, and embankments that
make Stockholm such a wonderful
destination today.
Ironically, much of the wealth
that made these improvements
possible, came from the exploitation
of their country’s natural resources.
case with proponents of nature-
based solutions. While they are
quick to highlight the social and
ecological costs of projects such as
dam building, they are less willing
to apply the same principle to their
approaches.
Take the case of wetlands that
can, indeed, solve a variety of water
problems. They can slow down
floods, and store and release wa ter
for use in dry periods. Research in
South Africa and elsewhere has
shown how artificial wetlands can
remove many pollutants from water,
although not enough to make it safe
for human use.
However, to reduce flooding
events, large areas of land must be
set aside to be inundated — and land
is a scarce and expensive resource in
the world’s cities. And while wetlands
can store and release a steady flow
of water, they lose large volumes
to evaporation — evaporation from
the Okavango swamps in Botswana
is almost as large as the flow of the
entire Orange River!
The biggest cost of wetlands,
however, is probably their impact
on climate change. The chemical
processes that remove organic
pollution also produce lots of
methane, a greenhouse gas that
is more than 40 times more potent
than CO 2 (although, fortunately, not
as long-lived in the atmosphere).
The IPCC (the UN’s climate agency)
reports that wetlands are the largest
single source of methane — and
an important contributor to global
warming.
Perhaps the most important
contribution
of
nature-based
solutions is what they teach us about
the design of built infrastructure. So,
we mimic nature, producing fertiliser
Often, once water has been used, the waste, along with assorted human and other waste,
is often dumped into the nearest water course.
“Of course, the exploitation
of nature comes with
costs as well as benefits,
although these are often
conveniently forgotten.”