Africa Water, Sanitation & Hygiene September - October 2016 Vol. 11 No.4 | Page 15
Water Treatment
Cities face dramatic increase in water treatment
spending when watersheds are developed
River Irvine at Irvine
Global costs reach US $5.4 billion annually
A
new global study has found that one in three large
cities spend 50 percent more on water treatment
costs as a result of damage to the ecological quality of
their watersheds.
This study found that urban source watershed degradation
is widespread globally, with 9 in 10 cities losing significant
amounts of natural land cover to agriculture and
development in the watersheds that supply their drinking
water. This has led to polluted water and an increase in
water treatment costs that represent a liability in excess of
US $100 billion (net present value).
“This increase in cost matters because increases in watertreatment costs are paid for by those living in cities, so
watershed degradation has had a real cost for hundreds of
millions of urbanites,” said Rob McDonald, lead scientist
for The Nature Conservancy’s Global Cities program.
Urban water treatment costs rise when the water quality
at the source of a city’s drinking water is affected by how
the land in the watershed is used. Intact forests and other
natural ecosystems protect water quality in a way that
farms and residential neighborhoods cannot.
“Estimating watershed degradation over the last century
and its impact on water-treatment costs for the world’s
large cities,” was published July 25 in the peer-reviewed
journal Proceedings of the National Academy of
Sciences (PNAS), and coauthored by McDonald, his
fellow scientists Tim Boucher and Daniel Shemie from
The Nature Conservancy and colleagues from Yale and
Washington State universities.
As the world grows more urban -- with more two-thirds
of the world’s population expected to live in cities by 2050
-- and climate change drives droughts and water shortages,
protecting drinking water for city residents will be an
increasing challenge for municipal leaders.
This study demonstrates the critical role that nature can
play in ensuring clean, safe drinking water with an analysis
of new global data about the sources of cities’ drinking
water and information about population growth and land
use change over the period of 1900-2005.
“City leaders can use our findings to advocate for
protecting t