Transcript PPT, 1.3 MB - START - SysTem for Analysis Research and Training

Capacity Building in Analytical Tools for
Estimating and Comparing Costs and
Benefits of Adaptation Projects in the
Berg River Basin, South Africa
Group AF-47
Daan Louw, Molly Hellmuth, Mac Callaway, Jabavu Nkomo, Debbie Sparks
AIACC African Workshop
Dakar, Senegal, March 2004
ERC
Energy Research Centre
Participating Organisations
* Energy Research Centre, University of
Cape Town, South Africa
* Department of Water Resources, Banjul,
The Gambia
* UNEP- Risø Centre on Energy, Climate and
Sustainable Development, Denmark
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
The Project Areas…
The Gambia
The Berg River Basin,
South Africa
Cape Town
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
The Berg River Basin, South Africa:
The Context
• The Berg River basin provides water to both the Cape Town
urban center and a variety of irrigation crops.
• In 1999, the managed demand on the dams of the Western
Cape System was 457 MCMs/a compared to the yield of about
442 MCMs
• Winter rainfall region: April – September, need for storage
capacity, farm dams and other large
• The decision to build the Berg River dam is controversial – is it
needed?
• The impact of climate change was not considered in the dam
feasibility assessment
• The total (holistic) economic impact of building new dams – not
considered
• The impact of the new National Water Act (1998): a major push
to create water markets in South Africa (there is provision for
water trading, a reserve)
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
The Berg River Basin, South Africa:
Objectives
• Estimate the potential impacts of alternative climate
change scenarios on water supply and demand in the
basin due to changes in runoff, evapotranspiration and
surface evaporation,
• Translate these physical impacts into monetary losses
(or gains) for different groups of farmers and urban
water users,
• Estimate and compare the benefits costs of the storage
and water market options (‘adaptations’) of avoiding
climate change damages under different climate
scenarios
• Estimate the risk of making ex-ante planning decisions
with different than expected ex-post climate outcomes
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
The Berg River Basin, South Africa:
Schematic
CLIMATE
IMPACTS:
Runoff, Crop
Water
Requirements,
Surface
Evaporation
WatBal Model:
Rainfall/Runoff
Model
ADAPTATION OPTIONS
Production and
Resource
Allocation
Upper Berg River
Spatial Equilibrium
Model
COSTS/BENEFITS
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
MANAGEMENT/
INVESTMENT
DECISIONS
The Berg River Basin, South Africa:
Schematic
CLIMATE
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
Climate
• HAD A2* GCM Reference (1961 –1990), Near (20102039) and Distant (2070-2099) future time periods
180
Reference Period
Near Future
Distant Future
Precipitation, mm
140
100
60
20
jan
ERC
Energy Research Centre
feb
mar
apr
AIACC African Workshop
Dakar, Senegal, March 2004
may
jun
jul
aug
sep
oct
nov
dec
The Berg River Basin, South Africa:
Schematic
CLIMATE
IMPACTS:
Runoff, Crop
Water
Requirements,
Surface
Evaporation
ERC
Energy Research Centre
WatBal Model:
Rainfall/Runoff
Model
AIACC African Workshop
Dakar, Senegal, March 2004
Preliminary Impact Results
• This CC scenario results in a decrease in runoff over
the basin
• An increase in Potential EvapoTranspiration losses
– Higher crop-water use; Higher Evaporation Potential from
Storage
40
Reference Period
Near Future
Distant Future
Runoff, MCM
30
20
10
0
jan
feb
ERC
Energy Research Centre
mar
apr
may
jun
jul
aug
sep
AIACC African Workshop
Dakar, Senegal, March 2004
oct
nov
dec
The Berg River Basin, South Africa:
Schematic, cont…
CLIMATE
IMPACTS:
Runoff, Crop
Water
Requirements,
Surface
Evaporation
Production and
Resource
Allocation
ERC
Energy Research Centre
WatBal Model:
Rainfall/Runoff
Model
Upper Berg River
Spatial Equilibrium
Model
AIACC African Workshop
Dakar, Senegal, March 2004
The Berg River Basin, South Africa:
Economic Model
Upper Berg River Spatial
Equilibrium Model is an
optimisation model that will
simulate:
•Competition for water
between urban and agricultural
water use over space and time
•Ex-ante investment in
additional reservoir capacity
•Ex-post reservoir operation to
meet urban, agricultural and
environmental demands for
water
•Objective function is based on
economic efficiency, but model
can also simulate alternative
allocation systems.
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
The Berg River Basin, South Africa:
Adaptation Options
• Consider specifically:
– Markets– develop a system of water rights
– More storage (at an economically optimal level)– collective
autonomous adaptation– by farmers and/or government
– Marginal costs of environmental “reserve” flow
• Scenarios:
– Current climate
– Climate Change Scenarios (downscaled GCM, “what if”)
– Partial Adjustment (reservoir capacity and institutions fixed,
farm and reservoir management variable)
– Full adjustment (reservoir capacity and institutions are also
variable, partially and in combination)
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
The Berg River Basin, South Africa:
Schematic
CLIMATE
IMPACTS:
Runoff, Crop
Water
Requirements,
Surface
Evaporation
WatBal Model:
Rainfall/Runoff
Model
ADAPTATION OPTIONS
Production and
Resource
Allocation
Upper Berg River
Spatial Equilibrium
Model
COSTS/BENEFITS
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
MANAGEMENT/
INVESTMENT
DECISIONS
The Berg River Basin, South Africa:
Evaluating Costs and Benefits
• COSTS (over 30 year time period):
– Changes in farm production costs
– Changes in investment costs for new
capacity
– Changes in administrative costs associated
with water market transfers
• BENEFITS:
– Changes in willingness to pay for water by
farmers and urban users (PV) – efficiency
increases
– Benefit of delay in new storage
ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004
Conclusions
• The methodology allows us to:
– Estimate climate change damage without the alternatives
(additional storage capacity, water markets, both) and
– Estimate benefits and costs associated with reducing climate
change damages for each alternative for each and multiple
climate change scenarios
– Determine the optimal storage capacity for each and multiple
climate change scenarios
– Estimate the cost of making ex-ante decisions about reservoir
capacity, if the climate change scenario turns out to be wrong
ex-post
– Minimizing the cost of making these mistakes
• Preliminary impacts results indicate an expected
reduction in runoff, which will exacerbate the existing
water scarcity
AIACC African Workshop
ERC
Energy Research Centre
Dakar, Senegal, March 2004
End
Thank you, for more information contact:
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Or, please visit:
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ERC
Energy Research Centre
AIACC African Workshop
Dakar, Senegal, March 2004