Geoscience Reference
In-Depth Information
Table 8.3
Predicted impacts of climate change on water resource management area
Water resource area
Predicted impact
River flows
There is a high level of confidence that by mid-21st
century, annual average river runoff and water
availability are projected to increase by 10-40% at
high latitudes and in some wet tropical areas, and
decrease by 10-30% over some dry regions at
mid-latitudes and in the dry tropics, some of which
are presently water stressed areas.
Hydrological extremes (floods and droughts)
There is a high level of confidence that drought-
affected areas will increase in extent. Heavy
precipitation events, which are very likely to increase
in frequency, will augment flood risk.
Snow and ice cover
There is a high level of confidence that over the course
of the 21st century, water supplies stored in glaciers
and snow cover will decline.
Forest production
There is medium confidence that globally, commercial
timber productivity will rise modestly with climate
change in the short- to medium term, with large
regional variability around the global trend. This may
affect water yield from forestry-covered catchments.
Coastal flooding
There is very high confidence that many millions more
people will be flooded every year due to sea-level rise
by the 2080s. The numbers affected will be largest in
the mega-deltas of Asia and Africa, while small
islands are especially vulnerable.
Source
: IPCC (2007)
Arnell and Reynard (1996) used models of river flow
to try and predict the effects of differing climate
change predictions on the river flows in twenty-one
river catchments in Great Britain. Their results
suggest a change in the seasonality of flow and also
considerable regional variation. Both these changes
are by and large driven by differences in pre-
cipitation. The North West of England is predicted
to become wetter while the South East becomes
drier. Overall it is predicted that winters will be
wetter and summers drier. This may place a great
strain on the water resources for south-east England
where by far the greater percentage of people live.
In a more recent study Arnell and Reynard (2000)
have suggested that flow duration curves are likely
to become steeper, reflecting a greater variability
in flow. They also predict an increase in flood
magnitudes that in the case of the Thames and River
Severn have 'a much greater effect than realistic land
use change' (Arnell and Reynard, 2000: 21). These
changes in river flow regime have important
implications for water resource management in the
future.
In non-temperate regions of the world predictions
vary on climate change. Parry (1990) suggests
rainfall in the Sahel region of Africa will stay at
current levels or possibly decline by 5-10 per cent.
Parry (1990) also suggests a 5-10 per cent increase
in rainfall for Australia, although this may have
little effect on streamflow when linked with
increased evaporation from a 2°C temperature rise.
Chiew
et al
. (1995) highlight the large regional
variations in predictions of hydrologic change in
Australia. The wet tropical regions of north-east
