Annex 2
EVIDENCE FROM THE CENTRE FOR ECOLOGY AND
HYDROLOGY (CEH)
1. Are Existing Water Supplies Adequate, and
what Additional Sources of Water Might be Needed?
Work for the Environment Agency and UKWIR found
significant reduction in low flows of up to 20% under some climate-change
scenarios by the 2020s. These impacts were simulated using the
four UK Climate Impact Programme scenarios (UKCIP02). It is difficult
to draw conclusions about the adequacy, or not, of current water
supplies given the catchment-specific response to climate change
and the somewhat limited geographic coverage of the study catchments
used. Also, the results were based on the output of just one Global
Climate Model (GCM) and scenarios from other GCMs would undoubtedly
produce different impacts on low flows (see uncertainty section
below).
2. What will be the Impact on Resource Management
(and Particularly the need for Changes in Irrigation and Water
Conservation for Agriculture)?
In southern England there will be greater competition
for water for agriculture, public water supply, industry and wildlife
conservation, and a greater risk of 1976-type summer droughts.
For agriculture, the main impact will be on
the costs of producing irrigated crops, especially potatoes, land
values near water supplies, river flows and water quality, and
private water supplies.
Adaptive measures that are required are:
(i) support for the construction of on-farm
reservoirs, including amending the Reservoirs Act so that there
are fewer costly obligations on farmers and planners;
(ii) incentives for water-efficient trickle
irrigation;
(iii) continuing survey of irrigators and
monitoring of groundwater, and
(iv) the development of "dirty"
water recycling technology.
3. What are the Implications for Flood Management,
Investment in Mitigation Measures, and for Wider Policy such as
Planning?
The DTI ForeSight initiative for Flood and Coastal
Defence, within which CEH has participated in both scientific
and advisory roles, was set up "to produce a challenging
and long-term vision for the future of flood and coastal defence".
This study takes account of the many drivers of future flood risk,
including climate change, incorporating the uncertainties, and
will be used as a basis to inform policy and its delivery. The
project reports in April 2004.
At CEH a number of studies have been undertaken
addressing the issue of climate- change impacts on flooding in
Britain. These studies have directly informed Defra policy on
climate change and flooding through their Project Appraisal Guidance
notes, and provided the scientific basis for the current guidance
of a 20% sensitivity allowance for climate change during flood-defence
scheme appraisal. Application of the UKCIP02, and of other scenarios,
has just been presented to Defra and the Environment Agency. This
work found a significantly reduced impact on flood flows than
had been previously modelled under earlier scenarios. Again, these
represent scenarios based on just one GCM and alternative GCMs
would produce different impacts on flooding (see uncertainty section
below).
(See: REYNARD, N S, BROWN, S, CROOKS, S M &
KAY, A L 2003. Climate change and flood frequency in the UK: An
appraisal of the 20% allowance in the light of the UKCIP02 scenarios.
Proc 38th Defra Flood and Coastal Management conference, Keele
University, July 2003. 05.5.1-05.5.12).
3.1 Uncertainty
The modelling methodologies developed for the
studies described above provide the framework for future developments.
The extension of these techniques to ungauged catchments will
allow national assessments to be undertaken. Scenarios of future
climate change will continue to be updated, from a range of GCMs,
Regional Climate Models, and from improved downscaling techniques,
and these will need to be applied to assess their impact on flood
and low flows. It is important that studies such as these sample
from as much of the uncertainty as is possible, and it is particularly
vital to consider those areas where uncertainty is large enough
to influence the decision or development of policy that the science
has been designed to inform. This is particularly the case for
using the outputs from more than one GCM.
The impacts of climate change on flooding need
also to address the wider flood risk measures of flood levels
and extents through linking hydrological with hydraulic models.
Climate change over the next 100 years cannot be treated as separate
from other environmental change. Changes in land use need to modelled
in combination with changes in climate, therefore requiring the
alignment of the science in this type of study with the research
in projects such FD2114 within the Defra/EA joint R&D programme.
4. How can the Impact of Changes in Water
Availability on Biodiversity be Minimised?
One way in which the future effects of climate
change on in-stream biodiversity can be predicted is through physical
habitat modelling. Recent research into development of physical
habitat modelling at CEH has been driven by the Water Framework
Directive, which requires river management at the catchment scale.
Methods have been developed at CEH which enable prediction of
the effects of future hydrological scenarios (such as abstractions
or climate change) on river habitat for fish. Up-scaling from
micro to catchment scale is achieved by integrating habitat modelling
approaches with catchment-scale hydrological models.
(See: BOOKER, D J, DUNBAR, M J, ACREMAN, M C,
AKANDE, K (2004), Catchment-scale physical habitat assessment.
Proceedings of the 5th International Ecohydraulics conference,
Madrid, Sept 2004.)
Another recent study by CEH considered how climate
change might affect the biodiversity of wet grasslands, using
the North Drain, a tributary of Brue catchment in Somerset, as
a test case. The study aimed to examine the ecological and biodiversity
impacts of a number of potential new management strategies for
such lowland wetland areas of Britain. In the past such regions
were extensively drained in order to maximise agricultural production.
Now that the country is consistently over-producing many of the
staple agricultural products, the study examined the potential
for changing the management of these predominantly dairy farming
areas in order to improve biodiversity, albeit at the expense
of agriculture to some extent. The study considered whether sufficient
water would be available during the drier summer months to maintain
higher water levels in the drainage channels in order to keep
soil moisture sufficiently high to maintain a richer biodiversity.
The study examined likely rainfall and flow patterns under a changed
climate and concluded that management of the area could be changed
to benefit biodiversity without adversely affecting downstream
water requirements.
(See: ACREMAN, M C, MOUNTFORD, J O, McCARTNEY, M
P, WADSWORTH, R D, SWETNAM, R D, McNEIL, D D, MANCHESTER, S J,
MYHILL, D G and BROUGHTON, R K, (2002). Integrating wetland management,
catchment hydrology and ecosystem functions. CEH Internal report
on Project C01163.)
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