Memorandum submitted by the Institution
of Civil Engineers
CLIMATE CHANGE AND WATER SECURITY
The Institution of Civil Engineers (ICE) is
a UK-based international organisation with over 75,000 members
ranging from professional civil engineers to students. It is an
educational and qualifying body and has charitable status under
UK law. Founded in 1818, ICE has become recognised worldwide for
its excellence as a centre of learning, as a qualifying body and
as a public voice for the profession. It has long been the role
of civil engineers to plan, promote, design, construct and manage
water resources and flood management schemes.
1. INTRODUCTION
The primary impact of climate change for the
water industry in the UK is predicted to be in water quantity.
By its very nature the water industry is required to take a precautionary
approach to water supply and wastewater treatment and the infrastructure
that supports these services, since the water companies have a
duty to supply water and must maintain continuity of water supplies
whatever the water resource situation. The Environment Agency
(EA) and the industry are also required take a precautionary approach
towards the environment.
The impact of climate change has significant
implications for the services provided by both the water supply
and wastewater businesses and the EA. Much has been written about
the climate change effects upon the supply of water, but of equal
consequence are the potential impacts upon water quality which
has a direct effect upon the quality and quantity of water available
for treatment for supply.
The ICE believes that there are several areas
where further research is needed, some more urgently than other.
The Foresight project into Flooding is a template that we recommend
be adopted for climate change as a subject in its own right. The
support of the Government Chief Scientist would be welcomed.
2. WHETHER EXISTING
WATER SUPPLIES
ARE ADEQUATE
AND WHAT
ADDITIONAL SOURCES
OF WATER
MIGHT BE
NEEDED
2.1 CURRENT WATER
SUPPLIES
Since privatisation of the water companies,
and now that they can, under certain circumstances, compete with
each other there is less information in the public domain on which
to judge whether existing water supplies are adequate. However
it can be said that England and Wales only utilise less than ten
per cent of available water. It is not therefore a question of
lack of water per se, rather it is variability of rainfall
patterns and limited storage of winter water, often coupled with
density of population in areas with less rainfall such as the
south east and river systems that are not spread evenly across
the country.
2003 was, in some parts of the country, a long
dry summer. According to CEH Wallingford the rainfall for the
period February to October over England and Wales as a whole had
a return period of over 30 years with some regions with a return
period of over 80 years. However no water company had to restrict
supply. This is due in part to the work that has been carried
out in recent years to improve efficiency of water resources by
interconnecting supplies and, in the last eight years, by reducing
leakage by about one third. Whilst all droughts are different,
this event did indicate that current water supplies are adequate
under the relatively severe conditions that prevailed.
2.2 WATER RESOURCES
PLANS FOR
THE FUTURE
For the purpose of future planning and to justify
funding approval sought from OFWAT under the AMP4 process, water
companies have developed 25 year water resource plans. These are
produced under the guidance and for consideration and approval
by the EA. These also are not in the public domain although certain
extracts and the EA's general comments on the draft submission
are available.
2.3 DROUGHT MEASURES
Historically water companies' resource plans
were based on a 2% risk, ie a drought that should only occur once
in 50 years. Thus there is risk that measures would need to be
taken whenever a drought of greater severity occurred.
In droughts with any degree of severity, water
companies now implement a planned approach to reduce demand and
increase supply. Companies analyse a dry year demand and compare
this to their available water along with a contingency. A standard
of service is set which is typically based upon a hosepipe ban
not occurring more often than once in ten years. Historically
when such droughts have occurred, the water company affected would
implement a planned approach to reduce demand. This is done by
use of the media to exhort customers to use less, followed by
hosepipe bans then followed by restrictions on public use of water
in car washes, golf clubs and sports fields and such means. Only
very rarely have any companies had to resort to further measures
such as real restrictions on use or stand-pipes. In today's industry
such measures as rota cuts or stand-pipes would not be acceptable
and tankering large quantities of water would only be an option
"in extremis".
Supply measures include Drought Permits and/or
Drought Orders, which usually include modifications to abstraction
licences which allow companies to take more from rivers even under
very low flow conditions or more from ground water sources. These
have an impact on the environment. Under climate change conditions
the EA may become more concerned about the effect on the rivers
and less keen to support Drought Orders, thus placing supplies
under even more pressure.
2.4 LONGER TERM
PLANS AND
CLIMATE CHANGE
EFFECTS
The EA has produced guidance for the framework
and methodologies for the preparation of long term water resource
plans. Since these have to be submitted to the EA for approval
and that will not be given unless the plans are in accordance
with them they are in effect mandatory and prescriptive.
These water resource plans are for 25 years.
This period is needed as it can take 20 to 25 years to bring a
new reservoir through the preparation, investigation, environmental
studies, promotion and the planning process, including if necessary
appeals, through to, design, construction and filling stages.
The EA guidance takes account of the UKCIP02
scenarios. The UKCIP02 Report shows mean annual rainfall over
England and Wales by 2020 barely changing with some regions falling
and some regions rising. Winter rainfall rises by less than 10%
and summer rainfall falls by 10% to 20%. However the increased
temperatures mean that evapotranspiration also increases. This
means that more of the rainfall that lands is evaporated back
into the atmosphere. This effect has been studied by Professor
N. Arnell for UKWIR. This study shows late summer mean monthly
river flows reduce by up to 34% by the 2020s, with only a marginal
increase in winter flows. The much lower end-of-summer flows mean
that water supplies relying on direct abstraction from the river
during summer would be appreciably affected. The reduced summer
flows would also have a significant effect on water available
from single season critical storage reservoirs. The EA guidance
refers to the UKWIR Report.
This work had been based on the changes to average
monthly figures. What water planners need to know is not average
conditions, but how will conditions change in a critical dry period.
The UKWIR Report suggests that flows be adjusted by the same percentage.
The CCDeW Report on Climate Change Report states on page 168 "There
is growing awareness that models based on average climate change
may under-report the risks associated with climate change- particularly
the risk associated with the higher frequencies of unfavourable
conditions and extreme events . . . First the climate scenarios
provided by the UKCIP did not adequately address extreme events.
The project did not feel competent (or have the mandate) to extend
the scenarios with explicit changes in the variability of future
climates. Nor were estimates of changes in the frequency of extended
droughts available."
The EA guidelines confirm this on page 132 "For
water resources planning purposes it is possible only to estimate
the effect of climate change on average supply rather than on
the volume available in peak periods."
In our view this needs further investigation
and a sufficient precautionary allowance for climate change specifically
made in water resources plans. It has to be remembered that supply
must continue even in dry periods that will occur within the climate
change scenarios due to natural climate variability.
2.5 GROUNDWATER
AND CLIMATE
CHANGE
About a third of public water supply is taken
from groundwater aquifers. It should be noted that in many areas
of the country, there is already over-abstraction of groundwater
and the water companies are having to make plans for reductions
in yields in areas where rivers are suffering from low flows in
summer under present climatic conditions.
Recharge to the aquifer only occurs when there
is no soil moisture deficit. Thus recharge normally only occurs
during the winter months. The higher temperatures mean that evapotranspiration
from the soil and vegetation continues later into the autumn meaning
that aquifer recharge would start later. Similarly the end of
the recharge period would come earlier in the spring. The UKWIR
Report shows that average annual recharge is expected to fall
by 5% to 15%. However there is as yet no firm information how
recharge would change in a dry period. The Environment Agency
guidance implies that it should be taken as falling by the same
amount as the average annual recharge. This may or may not be
true. Thus a significant risk is that in a dry year aquifer recharge
may fall by even more than the annual average.
2.6 DOMESTIC
USE OF
WATER UNDER
CLIMATE CHANGE
SCENARIOS
Under the climate change scenarios people are
likely to wash more and change their clothes more frequently.
Studies in England and Wales by CCDeW have indicated that total
domestic demand could increase by about 1% to 2% over a region,
and this is what the EA have put in their guidance. The upsurge
in interest in gardening means that many water companies are experiencing
very high summer peak demands as customers use hosepipes on their
expensive flower beds. The CCDeW report says that where garden
watering is a significant feature the increase could be higher,
(pages 44-47). The report also states on page 170 "it
seems plausible that at least some people would respond to warmer
weather by investing in their gardens, developing water features
and spending more time outdoors. This implies buying and using
more hosepipes, and maybe even in-ground pools." We are
concerned that the effect of climate change on peak summer demands
may not have been adequately taken account of.
2.7 OTHER FACTORS
OF CONCERN
We are concerned also that the following factors
may not have been adequately included in EA approach to the water
resource plans.
1. The Guidance suggests that to cater for
climate change all river flows should be adjusted by the same
percentage assessed as the change in the mean monthly figure.
There is no evidence we can find on this. It is quite possible
that the effect would not be linear and the impact could be significantly
worse.
2. Whilst the water available for abstraction
from rivers has been assumed to be that above a "hands off"
flow based on current climate conditions, a higher ambient temperature,
and hence a higher river water temperature, would mean that more
water would need to be left in the river to provide similar oxygen
conditions and thus maintain the environmental quality of the
river. Thus environmental flows would need to be increased. This
would reduce the water available for abstraction even further.
3. No parallel account appears to been taken
of the implications of the Habitats Directive or Water Framework
Directive consideration on flow reductions and groundwater yields
in the company plans due to delay in providing such criteria for
the AMP4 plans. This will result in any costs incurred in the
AMP4 period being logged up. This seems an unsatisfactory situation
given the timetable for AMP4.
4. No account has been taken for the potential
non renewal of time limited licences by the EA, especially when
the alternative is a new reservoir requiring much longer than
a six year review period to implement.
5. For groundwater the balance between rainfall
and recharge during the winter is delicate, and in a drought occasioned
by climate change, available water could drop by much more than
the mean percentage shown in the UKWIR Report.
6. Beyond 2020 the change in water resources
due to climate change is likely to accelerate. The Arnell Report
for UKWIR provides scaling factors based on a linear interpolation
between the mid 1070s and 2020. Thus the factor for 2030, the
final year of the plans, is 1.2 times the effect by 2020. The
EA Guidance requires the scaling factors to be used. However the
Report states on page 25 "Extrapolation beyond the 2020s
is more problematic, because the assumption that temperature increases
linearly is no longer valid: the rate of change between the 2020s
and the 2050s is greater than the rate of change between the 1961-1990
base and the 2020s, particularly for the high emission scenario."
Thus the water resources situation in 2030 could well be significantly
worse than assumed in the water company plans.
7. The EA Guidance states on page 137 "In
general, we would expect water companies to accept a higher level
of risk in future years than at present." We believe
that the risk referred to is risk of failure to be able to provide
water. The water companies have a duty to supply water both now
and in the future and this does not change, nor should it.
8. The CCDeW report on Climate Change states
"probably the single most important caveat of the findings
of this report is the poor understanding of the risk of extreme
events."
9. Under climate change conditions in catchments
will be modified over time, for example soils will crack and vegetation
patterns will change such that predictions based upon existing
models may no longer be appropriate. Further research is required.
2.8 NEW SOURCES
OF WATER
As has been stated earlier, less than 10% of
available water is presently used. The problems occur at present
where there is insufficient interconnectivity, insufficient storage
or the density of population is disproportionate to the available
groundwater or river water availability. A number of alternatives
are available. These include making much greater use of storage
as climate change will result in greater winter flows and much
reduced summer flows. It will become even more important to conserve
winter water. This is best done in reservoirs. Many post war reservoirs
are SSSIs and some are even internationally recognised as Ramsar
Sites of international environmental importance. Reservoirs can
also be used to release flows downstream and mitigate some of
the effects of reduced summer flows due to climate change.
For the last ten years the EA, has resisted
plans for new reservoir development, although at the end of 2003
the Chief Executive of the EA signalled a shift in attitude. There
is a period from about 1985 to 2020 when no new public water supply
reservoirs entered or will enter service. Reservoirs have many
other benefits to society including providing excellent facilities
for conservation, particularly of wetland habitat around the margins,
and recreation including fishing, sailing, walking, bird watching,
canoeing etc. A million people a year visit Carsington reservoir
in Derbyshire. There is a body of opinion prevalent in some environmental
NGO's that seems to regard all new reservoirs as detrimental.
This view is we believe incorrect and will need to be addressed
by well organised public information. Whilst we support economic
demand management where a new reservoir development is needed
the EA should now actively encourage it and ensure that its environmental
and recreation benefits are maximised.
Other options include making more use of desalination
as the technology becomes more cost effective, although it remains
counter intuitive as it is energy intensive and depends upon fossil
fuels and produces the very greenhouse gases which are leading
towards climate change.. A much greater re-use of treated wastewater
is also recommended particularly in coastal regions where flows
are presently released into the sea after extensive and expensive
treatment. Such flows, which begin as freshwater and often result
from large coastal conurbations could be fed back inland into
the river systems thus supporting summer flows and abstractions.
3 RESOURCE MANAGEMENT
3.1 LEAKAGE
Some 20% of water put into supply is lost as
leakage, although this has fallen by over 33% in the past decade.
Some of this is lost through pipe bursts and some pipe bursts
are caused by leakage. Pipe bursts can be triggered by freezing
conditions in winter and by shrinkage due to drying of the soil
in summer. Under climate change it would be reasonable to expect
less ground freezing in winter but more ground shrinkage in summer.
It is possible that burst levels in England and Wales would fall
overall but they could rise in parts of the country which are
more prone to clay shrinkage in summer than frost effects in winter.
3.2 IRRIGATION
The main areas of irrigation are parts of the
Midlands and East Anglia. According to the UKWIR report mean summer
rainfall would fall by about 10% to 12% by 2020 and mean potential
evaporation would increase by a similar amount. Thus the requirement
for irrigation water would increase by more than these figures
and the area needing irrigation would also extend. If irrigated
agriculture is to continue at a similar level to the present then
more water would be needed. The CCDeW Report page 135 estimates
"the impacts nationally are around +20% by 2020s."
In most places the EA no longer licences summer abstraction and
more on farm water storage would be required to store winter river
flow for use in summer.
There is some evidence that some farmers are
switching to mains water for use with drip feed and other similar
irrigation systems. The CCDeW report states "Although
nationally only 3% of this water comes from mains supply at present,
the proportion is as high as 20% in the south east and could grow
substantially where climate change impacts cause direct abstraction
to be restricted, with implications for water company resource
planning." If so then peak requirement on the public
water supply could rise appreciably in a dry spell, just the time
when supplies would be most stretched.
3.3 RIVER WATER
QUALITY
Climate change will also affect the quality
of water in rivers. Higher spring and summer temperatures will
increase the incidence of algal blooms. These have a detrimental
effect upon water treatment works both in terms of treatable quality
and quantity.
Lower summer river flows will mean that when
sewers overflow there will be less river flow to dilute the foul
flow. In addition each sewage treatment works has a standard which
its effluent has to reach so as not to pollute the river. These
standards are set considering the low flow rates in the river.
Under climate change river flows may well go down by about 30%
in many areas. This would mean that the sewage treatment works
would need to be up-rated to provide the improved effluent standard.
4. FLOOD MANAGEMENT
Climate change will have a significant effect
upon flooding and flood management. This will impact direct fluvial
flooding and foul flooding via the sewerage system.
4.1 RIVER FLOODING
The current Foresight research project on flooding
and coastal defence supported by the Government has highlighted
the additional need to consider climate change in the planning
of flood management. The Institution of Civil Engineers Presidential
Report of November 2001, "Learning to live with rivers"
indicated that the key climate change impacts would include the
changes in rainfall intensity for a given frequency and would
lead to more flooding. This has already been observed in many
catchments. The condition of the ground prior to any storm also
has a profound effect upon the run-off and hence the flooding
that ensues. Ground conditions will change under climate change
and have a corresponding impact upon flooding. In a DEFRA sponsored
report published in 2000, it was noted that although there are
regional differences, the impact of climate change could be to
increase the annual average damage across England and Wales from
coastal flooding by 400% and from river flooding by 200% by the
year 2075. (Ref D. Richardson; Civil Engineering May 2002) These
figures were produced prior to publication of the UKCIP report
in April 2002. A more recent paper by authors from the EA and
DEFRA states that "the present 20 year return period flow
is projected to occur about twice as frequently after 80 years
of climate change", the paper then goes on to say that "the
impact of climate change is less than would be projected using
the precautionary approach"
Daily rainfall in winter is predicted to increase
appreciably. PPG 25, published by DTLR in July 2001 states that
"Initial research has suggested that for the Thames and
Severn catchments increases in peak flows of up to 20% for a given
return period could be experienced within 50 years." Catchment
flood management plans will assist in providing the basis for
a holistic approach to flood risk management. The ICE has welcomed
the Foresight research project and awaits the final report, due
to be published later this month.
4.2 SEWER FLOODING
Evidence of climate change on the design of
sewers is within a recent report prepared by UKWIR entitled "Climate
Change and the Hydraulic Design of Sewerage Systems."
Only a two page summary is in the public domain. This states that
the main impacts under climate change will be wetter winters and
drier summers with more intense summer storms. The impact of wetter
winters will be to raise water tables by early spring and this
in turn could lead to surcharged sewer systems and consequential
domestic flooding with foul water. More intense summer storms
will also cause problems for the sewer system and also for river
water quality, with more discharges of untreated storm water feeding
into rivers and streams. The predicted magnitude of the impacts
by 2080 are available from UKWIR, who report an increase in rainfall
depths by up to 40%, an increase by up to 2.6 times in above ground
flooding and the storage necessary to contain these increased
run-offs being increased in turn 10 fold. These changes are in
themselves dramatic albeit they are towards the end of the period
under consideration; what is of concern is that investment in
the sewer systems over the past decade has been grossly insufficient
and the gradual increases associated with climate change will
put further stress on the system and cause a gradual increase
in the number of properties at risk of flooding. A important policy
issue is that if sewers are expected to last for several hundreds
of years then how much effect for climate change should be allowed
in the design of new sewers and the upgrading of existing sewers?
5. WAYS IN
WHICH THE
IMPACT OF
CHANGES IN
WATER AVAILABILITY
ON BIODIVERSITY
CAN BE
MINIMISED
This subject is not one on which civil engineers
are specialist. However we are aware that the higher river temperatures
may result in the loss of some species such as salmon in the Thames
which are believed to be at the limit of their tolerance. We consider
that it would be important to study the increase in river temperatures
that will occur and decide on the extent to which this can be
mitigated by other measures such as having a greater flow in the
river. It is possible that with the reduction in dissolved oxygen
in rivers due to higher temperatures and lower summer flows, there
will be a reduction in fish stocks. Such adverse effects may only
be able to be solved by increasing the treatment standards at
existing works at significant cost to the customer. One other
impact could be that river water cooling for power stations, such
as occurs on the River Trent, and for certain factories may have
to be restricted further.
Chris Binnie, Independent Consultant and Member
of ICE Water Board and Graham Setterfield, Independent Consultant
and Chairman of ICE Water Board
Institution of Civil Engineers
April 2004
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