The purpose of this position statement is to describe the issues
that apply to developing new public water supply reservoirs in the
UK. This document will set out CIWEM's position on developing these
new reservoirs and this will be used to inform future debates.
CIWEM calls for:
- A review of the planning process to ensure that the development
of large water infrastructure schemes is undertaken in a timely
- Where a new reservoir is included in the final Water Resources
Management Plan, after stakeholder consultation, this should be
recognised as an enabler to making the planning process more
- Early stakeholder engagement and continued consultation with
all relevant parties throughout the planning, design and
construction of the scheme.
- Continual justification of need up to construction.
- Reservoirs only to be considered as part of a wider mix of
schemes including demand management options.
- Justification over all future scenarios using best available
- Maximisation of environmental, social and economic benefits
including the use of best practice mitigation measures.
The Chartered Institution of Water and Environmental
Management (CIWEM) is the leading professional body for the people
who plan, protect and care for the environment and its resources,
providing educational opportunities, independent information to the
public and advice to government. Members in 98 countries include
scientists, engineers, ecologists and students.
There are hundreds of reservoirs within the UK with a variety of
uses from public water supply, supply to inland waterways for
navigation, winter storage reservoirs for agriculture, generation
of hydropower, flood alleviation and river regulation.
The growth of large dam building for public water supply peaked
in the 1960's and today there are over 450 large dams for public
water supply in the UK, of which 80% are in upland areas.
The majority of these large dams were constructed during the
industrial revolution when the needs of industry and the health of
the population in the expanding industrial cities were paramount.
This often meant that the environmental consequences were given a
The last major public water supply reservoir to be constructed
in the UK for water supply purposes was Carsington in 1991, and
although a number of water supply reservoirs have been proposed
since the 1960's very few have made it to completion.
The reasons for this are complex and include an increased
awareness of the environmental consequences of large construction
schemes in general, and of the loss of flooded land in particular;
expressions of public concern; considerable effort on reducing
leakage, increased metering, increased efficiency of water using
appliances, Code for sustainable homes, greater demand management;
availability of other feasible options and improved regulation of
the water environment.
However, currently within the UK water companies are proposing a
number of new reservoir schemes. The reasons can mainly be
attributed to the pressures on water supply availability
experienced in recent droughts, reduction in supply due to need for
increased river flows to meet sustainability criteria, and to the
prospect of serious shortfalls in the future, under many climate
change scenarios. Water companies produce water resource
management plans that describe how they will maintain security of
supply over the planning horizon (normally 25 years). Each plan is
based on the principles of the twin track approach, which is a
range of measures to both reduce demand as well as improve
Key Issues - Discussion
Justification of Need
Water companies have done much to reduce the demands for water
including significant reduction in leakage as well as promoting and
implementing water efficiency measures.
The level at which it is no longer economical to continue to
reduce leakage is termed the "economic level" and some water
companies believe they can demonstrate that they have reached this
Water companies also have a duty to promote water efficiency and
have done much to raise public awareness and deliver improvements.
However, the government predictions of population growth,
especially in the South East and East Anglia, will place more
pressure on the water resources in these areas. The increased need
for water can be mitigated to a certain degree by water efficiency
measures including metering and water-efficient appliances but
there is still likely to be a residual increase in the demand for
water. There is some uncertainty around the achievable reduction in
demand that can be delivered by water efficiency measures
Water companies also face a reduction in the yield of some of
their existing water sources due to new environmental legislation
driving improvements in the status of our water environment. The
Environment Agency's review of abstraction licences ion England and
Wales is indicating that a number of catchments are currently
over-licensed or over-abstracted including a number of designated
sites (SACs and SPAs) which are adversely affected by abstractions
for public water supply. The ecological flow requirements of
the Water Framework Directive will also reduce the amount of water
available from both surface and groundwater sources.
The contamination of some groundwater sources is likely to
reduce the yield available from some groundwater sources and/or
increase the costs of treatment.
The predictions of climate change on water resource yield,
although containing much uncertainty, suggest that summer rainfall
will be lower and so water availability for abstraction from
existing supplies in periods of peak demand will be reduced.
The consequence of these demand and supply side pressures have
resulted in some water companies identifying a need for significant
extra quantities of water and including new reservoirs in their
water resource management plans. For example Thames Water has
included a new reservoir in the Upper Thames catchment.
However, the initial inclusion in the water resource plan is
only the starting point of a process, which for a large capital
construction project such as a reservoir could take up to twenty
five years to reach final completion. This lengthy period of
studies, investigations, public consultation, public enquiries,
Secretary of State approval, design, construction and filling etc
means that when a new reservoir is initially proposed the
justification of need is based on assumptions with a great deal of
uncertainty. If approvals are granted with too much uncertainty
then reservoirs could be constructed which are not fully required.
With the environmental, social and economic consequences being so
great this is an unacceptable result. In the UK we do have examples
of this happening, e.g. Kielder Reservoir was hardly used for water
supply during the first 20 years of its life. It is therefore
important that proposals are supported by robust justification.
A reservoir will inundate a large area of land and alter the
environment of the reservoir site, surrounding land and any
upstream and downstream effects on the watercourse. The reservoir
proposer cannot mitigate fully this loss of habitat however the
environmental mitigation measures should seek to maximise
environmental benefits and minimise environmental costs.
The types of environmental benefit which can be derived include
creation of new habitats and improvements to wetlands. Best
practice approaches to environmental mitigation should always be
included in the scheme design. There are many best practice
examples around the UK and internationally and this should be seen
as a minimum requirement. The scheme should innovate and create
best practice. It should be an exemplar project for environmental
mitigation. It is essential that environmental stakeholders are
consulted very early in the consultation phase so that best
practice and innovation are delivered.
A reservoir will inevitably involve the loss of land and
depending on the location this may involve the loss of many
community benefits which resulted from this land. The proposer
should seek to minimise the cost and maximise the benefits to the
community of losing this land. A major part of this will be in the
site selection and it is important that a baseline survey of any
site identifies all the community and public benefits gained from
the land. This could include heritage and archaeology, leisure and
amenity, local history, wildlife, ecology etc.
One of the major issues regarding reservoir development can be
the displacement of people living in the area planned for
inundation. The site selection should minimise the number of people
that have to be displaced and also derive robustly the costs
associated with any displacement. This should not just include the
compensation costs to the individual but the full costs to the
community. Having reviewed a number of dams in developing
countries the World Commission on Dams advocated in 2000, amongst
many proposals, "participatory decision making" to gain public
acceptance and "free, prior, informed consent" of those affected to
ensure they really did gain from the scheme."
It is also important to recognise the increased risks to
communities downstream of the dam and ensure that these costs are
included. This may include increased flood risk associated with a
'worst-case scenario' possible failure of the dam and its effect on
the value of homes.
Many reservoirs attract large numbers of visitors to enjoy the
scenery and leisure facilities that a reservoir provides, including
walking, fishing, boating and visitor centres displaying local
interest information. There are examples where the social benefits
have been evaluated as greater than the environmental costs (after
The construction of such a large capital project as a reservoir
can realise economic benefits during all phases of the project from
design to the final running of the scheme. The benefits will apply
at a local, regional and national level and will include direct and
The development of a new reservoir will raise significant
interest from many stakeholders locally, regionally and nationally.
It is essential that these stakeholders are identified and engaged
in the process at a very early stage. If the new reservoir is to
gain support at public enquiry stage then the earlier in the
process the stakeholders are engaged the more likely a positive
outcome can be achieved.
The consultation should take many forms to ensure that all
stakeholders have been identified and engaged. The need to be
inclusive and targeted in the public relations strategy is
Water companies plan the strategic development of water
resources over 25 years. Each company's water resources management
plan will highlight any supply shortfall over the planning horizon
and outline the options available to deal with this supply
shortfall. These plans have historically only been sent to the
Environment Agency, OFWAT and the appropriate Secretaries of
State. However, the Water Act 2003 makes it a statutory duty
on the water companies to consult on these plans. If one of these
options is a new reservoir then detailed studies will be
commissioned to improve the justification of need. These studies
and investigations may take a number of years to complete and will
include consultation with stakeholders, communities and customers.
Provided the conclusion of these studies and consultations support
the continued justification for a new reservoir, the proposals will
be put forward for planning approval. Sometimes a public inquiry is
required before a decision is made on the planning application.
Note: CIWEM Policy Position Statements (PPS) represent the
Institution's views on issues at a particular point in time. It is
accepted that situations change as research provides new evidence.
It should be understood, therefore, that CIWEM PPS's are under
constant review, and that previously-held views may alter and lead
to revised PPS's.