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Chartered Institution of Water and
Environmental Management (CIWEM)

106-109 Saffron Hill, London, EC1N 8QS  
Tel: 020 7831 3110   Fax: 020 7405 4967

Climate Change & Water Resources In The UK


This Policy Position Statement (PPS) reviews the likely impact of climate change on water resources in the UK, and sets out the position of the Chartered Institution of Water and Environmental Management (CIWEM) on how water resources should be planned and managed in this context.

CIWEM calls for:

  • Professionals working in water resources and associated areas to make sure that they are aware of current thinking on climate change and its impact on their area of work.
  • Whenever a strategic or long-term decision about water resources management is being made, the possible impact of climate change must be considered.
  • When climate change is being considered in water resources decisions, care must be taken to ensure that decisions do not:
    - consider climate change as a factor when it should have no real influence;
    - fail to consider non-climate factors that have a greater influence than climate change;
    - fail to consider climate change when it may be central to making the most appropriate decisions.
  • In considering climate change in water resources decisions, the full range of possible future climate scenarios to be taken into account. It is not acceptable to choose a scenario because it is easier to manage or because it illustrates a point.
  • In considering climate change in water resources decisions, the impact on water quality to be considered - climate change may lead to more algal blooms, more storm surges leading to higher sediments entering rivers, and more low flow events. These problems should not be further aggravated by the option chosen.
  • A preference to be given to water resources options that are "no regrets" or "low regrets". Such options that will continue to be of value through the full range of possible future climates.
  • The impact of energy use to be considered in water resources decisions - there are opportunities to reduce energy use and the emission of greenhouse gases.  Reducing the demand for water is a good way to control energy use and options to reduce water use should be favoured.
  • The impact of climate change on the environment to be considered in water resources decisions - the environment will come under additional pressure as a result of climate change, and steps should be taken to reduce this as far as possible.
  • Further research into the ways that water resources and the water environment will be affected by climate change.
  • Further research into the socio-economic impact of climate change on water availability.
  • Policies and laws that reconcile the needs of the environment, people and businesses, and that are responsive to changing climatic conditions.
  • Clear communication to all water users on the effect of climate change on resources and the actions that they can take to conserve water and protect supply.


There can be little doubt that our climate is changing as a result of man's influence (see CIWEM's over-arching PPS on the subject, 'Global Climate Change'). The Intergovernmental Panel on Climate Change (IPCC) tells us that world wide, long-term changes will be significant and affect many different aspects of life. There is increasing evidence that the UK climate is already starting to change. Globally, the 1990s was the warmest decade of the last millennium. The present decade looks set to be even warmer than the 1990s.

The UK Climate Impacts Programme's 2002 scenarios suggest that winter rainfall will increase across the UK.  Summer rainfall may decrease by 30 to 50 percent by the 2080s.  The largest changes in precipitation in both summer and winter are in eastern and southern England, while changes are smallest in north west Scotland.

Extremes of weather are expected to become more common as a result of climate change, with more frequent storms and heatwaves. The impact of climate change on the frequency and severity of long droughts is less clear, but we must prepare to deal with weather patterns that we have not seen in the last century.

Predicting future climates is difficult and it is important to understand the uncertainties surrounding the scenarios. 

Key Issues - Water resources and climate change

Many aspects of water resources management will be affected by climate change.

Increased temperatures and more marked seasonality in river flows will cause additional stress to the water environment. Some species may thrive but other populations may be seriously damaged. The way that we use water will have an important part to play in protecting the environment in the future.

People's demand for water is affected by the weather. Hot, dry summers could lead to an increased demand for garden watering and personal washing. In a crowded island, unlimited supplies of water for non-essential uses should not be expected, and people can play an important part in adapting to future climates.

Agricultural demand for water may also increase. Irrigated crops are an important part of the UK's agricultural economy and it will be important to make sure that limited supplies of water are used effectively.

It seems likely that climate change will reduce the water available for public water supply. Reservoir yields may reduce and some groundwater sources could become less reliable. Droughts may be more frequent.  Short but intense summer season droughts may become much more frequent than they have been in the past.  Long, multiple year droughts may not be either more common nor less common than in the past, but when they do occur, they are likely to be more intense, and will place water resources systems under severe strain.

Adapting water supply for future climates will require imaginative solutions that minimise further emissions of greenhouse gases. These should favour resilience and flexibility. This may include developing some new reservoirs but it is by no means clear that this is the most appropriate solution. A full range of options must be considered. Demand management is an effective way of both improving resilience to climate change and reducing greenhouse gas emissions. This could include changes to the way that water is allocated between different uses and incentives for people and business to save water.

June 2007

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.


Chartered Institution of Water and
Environmental Management (CIWEM)

106-109 Saffron Hill, London, EC1N 8QS  
Tel: 020 7831 3110   Fax: 020 7405 4967