Wednesday, September 19, 2012

Zambezi hydro-dams unprepared for climate change

Dam-Dependent Zambezi Basin Unprepared for Climate Change

New report documents dangers of �business-as-usual� approach

An in-depth study warns that new and proposed dams on Southern
Africa�s largest river are ill-prepared to withstand the shocks of a
changing climate. The result could be uneconomic dams that under-
perform in the face of more extreme drought, and more dangerous dams
that have not been designed to handle increasingly damaging floods.

Currently, 13,000 megawatts of new large-dam hydro is proposed for the
Zambezi and its tributaries. The report finds that existing and
proposed hydropower dams are not being properly evaluated for the
risks from natural hydrological variability (which is extremely high
in the Zambezi), much less the risks posed by climate change.

Dr. Richard Beilfuss � a noted hydrologist with extensive experience
on the Zambezi � evaluated the hydrological risks to hydropower dams
in the basin. Overall, Africa�s fourth-largest river will experience
worse droughts and more extreme floods. Dams being proposed and built
now will be negatively affected, yet energy planning in the basin is
not taking serious steps to address these huge hydrological

�Ensuring energy and water security in the Zambezi River basin for the
future will require new ways of thinking about river basin
development,� notes Dr. Beilfuss. �We must avoid investing billions of
dollars into projects that could become white elephants.�

The report�s key findings describe a region moving toward the edge of
a hydrological precipice:
� The Zambezi basin exhibits the worst potential effects of
climate change among 11 major sub-Saharan African river basins, and
will experience the most substantial reduction in rainfall and runoff,
according to the International Panel on Climate Change. Multiple
studies estimate that rainfall across the basin will decrease by 10-15%.
� The basin is likely to experience significant warming and
higher evaporation rates in the next century. Because large reservoirs
evaporate more water than natural rivers, big dams could worsen local
water deficits (and reduce water for hydropower). Already, more than
11% of the Zambezi�s mean annual flow is lost to evaporation from
large hydropower dams� reservoirs. These water losses increase the
risk of shortfalls in power generation, and significantly impact
downstream ecosystem functions.
� The designs for two of the larger dam projects proposed for
the Zambezi, Batoka Gorge and Mphanda Nkuwa dams, are based on
historical hydrological records and have not been evaluated for the
risks associated with reduced mean annual flows and more extreme flood
and drought cycles. Under future climate scenarios, these hydropower
stations, which are being based on the past century�s record of flows,
are unlikely to deliver the expected services over their lifetimes.
� The occurrence of more frequent extreme floods threatens the
stability and safe operation of large dams. Extreme flooding events, a
natural feature of the Zambezi River system, have become more costly
downstream since the construction of large dams. If dams are �under-
designed� for larger floods, the result could be serious safety risks
to millions of people living in the basin.

� The Zambezi River is already highly modified by large
hydropower dams, which have profoundly altered the hydrological
conditions that are most important for downstream livelihoods and
preserving biodiversity. The ecological goods and services provided by
the Zambezi, which are key to enabling societies to adapt to climate
change, are under grave threat. A recent economic study estimated that
the annual total value of river-dependent ecosystem services for one
Zambezi floodplain (the Zambezi Delta) ranges between US$930 million
and $1.6 billion. The economic value of water for downstream ecosystem
services exceeds the value of water for strict hydropower production.
These services are not being properly valued in planning for large
dams in the basin.

Rudo Sanyanga, Africa Programme Director for International Rivers,
says: �Large-dam hydro poses not just economic risks, but also
adaptation risks. Africa has been called the continent �most at risk�
of climate change. Successful adaptation will require new ways of
thinking about water resources. We need to act now to protect our
rivers as sources of livelihoods and food security.�
The report recommends a series of steps to address the coming storm of
hydrological changes, including changes to how dams are planned and

Read the report: �A Risky Climate for Southern African Hydro:
Assessing hydrological risks and consequences for Zambezi River Basin
dams� by Dr. Richard Beilfuss. Full report, executive summary and
supporting materials (some in Portuguese as well as English) here:

View a short video on the report�s findings:

Biographical information for Dr. Beilfuss:

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