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| Table 4-10: Effect of climate change on navigation
opportunities on River Rhine (Grabs, 1997). |
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Average Annual Number of Days
when Large Boat-Trains can Move
(flows between 2000 and 5500 m3 sec-1 )
|
|
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UKHI
|
CCC
|
|
|
|
1990
|
168
|
|
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2020
|
164
|
170
|
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2050
|
156
|
170
|
|
2100
|
148
|
166
|
|
Kaczmarek et al. (1996) assessed the impact of climate change on the water
supply system in the Warta River basin in Poland, looking at two climate change
scenarios in the context of increasing demand for water (particularly from irrigation).
In the absence of climate change, they show that there would be supply problems
in part of the system by 2050, simply because of the increase in demand. Under
one of the scenarios, inflows to supply reservoirs would increase sufficiently
to prevent supply problems; under the other scenario, the risk of shortage would
increase substantially (the probability of an annual deficit of 10% would increase
from 4 to ~25%, for example). Kaczmarek et al. (1996) also looked at the feasibility
of one adaptation option—transferring water from one reservoir to another—and
showed how it could lessen the likelihood of shortage.
The River Rhine is a very important transport route within Europe. Grabs (1997)
considered the effect of two climate change scenarios on navigation opportunities,
having translated climate into streamflow by using a catchment water balance
model. Table 4-10 summarizes the results: Under one of
the scenarios, there would be little obvious effect on navigation opportunities,
but under the other movement could be curtailed, particularly by the middle
of the 21st century.
The vast majority of the impact assessments in Table
4-8 describe the effects of climate change on the reliability of an existing
system. Very few explore the costs of these impacts, primarily because of difficulties
in deciding the basis for calculation. Are the costs of climate change equal
to the cost of continuing to provide the current standard of service? Are the
costs of services foregone (in terms of extra flood damages or reduced use of
water), or are they incurred in providing services at a new economically-optimum
level? In other words, estimates of the cost of climate change must consider
explicitly the measures used to adapt to that change, and the economic costs
of climate change will depend on the adaptation strategies adopted. Carmichael
et al. (1996) present one of the few studies that has tried to cost the implications
of climate change. They investigated the treatment costs necessary to maintain
a given water quality standard (expressed in terms of dissolved oxygen content)
in a river in Slovakia and calculated the least costly treatment under the present
hydrological regime and under one scenario for the 2020s. They showed that costs
would be little different if the aim were to meet a 4 ppm dissolved oxygen target
under average summer conditions but would rise by a factor of about 14 (at current
prices) if the aim were to meet the same target under low-flow conditions, even
taking a least-cost approach.
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