Policy 5.15 Water use and supplies
A The Mayor will work in partnership with appropriate agencies within London and adjoining regional and local planning authorities to protect and conserve water supplies and resources in order to secure London’s needs in a sustainable manner by:
a minimising use of mains water
b reaching cost-effective minimum leakage levels
c in conjunction with demand side measures, promoting the provision of additional sustainable water resources in a timely and efficient manner, reducing the water supply deficit and achieving security of supply in London
d minimising the amount of energy consumed in water supply
e promoting the use of rainwater harvesting and using dual potable and grey water recycling systems, where they are energy and cost-effective
f maintaining and upgrading water supply infrastructure
g ensuring the water supplied will not give rise to likely significant adverse effects to the environment particularly designated sites of European importance for nature conservation.
B Development should minimise the use of mains water by:
a incorporating water saving measures and equipment
b designing residential development so that mains water consumption would meet a target of 105 litres or less per head per day
C New development for sustainable water supply infrastructure, which has been selected within water companies’ Water Resource Management Plans, will be supported
5.60 Water supplies are essential to any sustainable city and to the health and welfare of its people. London’s consumption of water already outstrips available supplies in dry years and ensuing a sustainable and secure water supply has to be an urgent priority. Some steps have already been taken. Investment in recent years to reduce leakage from Victorian mains supply pipes has had an effect (although Thames Water still has a significantly higher leakage rate than the rest of the country). An additional source of supply, the desalination plant at Beckton, has been operational since 2010. These two measures have eased the pressure on water resources in London.
5.61 But the fundamental problem remains. To remain sustainable, London needs to reduce the level of water consumption per person. Currently the average Londoner consumes 164 litres/day (l/d), around 20 l/d above the national average. Projections for population growth in London and in the wider south-east will mean that over the period of this Plan, new strategic water resources will be required. The need for this is exacerbated by the climate change predictions of more sporadic and intense rainfall and a higher likelihood of droughts as well as the need to protect the water environment implementing the Thames River Basin Management Plan requirements. Thames Water, which provides over three-quarters of Londoners with water, projects a significant (around 6% by 2020) capacity deficit. To ensure London’s future water security, the prudent use of water will be essential: all new development will need to be water efficient. Residential development should be designed so that mains water consumption would meet a target of 105 litres or less per head per day, excluding an allowance of 5 litres or less per head per day for external water use. This reflects the ‘optional requirement’ set out in Part G of the Building Regulations. As all water companies that serve London are located in areas classified as seriously water stressed, the ‘optional requirement’ should be applied across London. A fittings-based approach should be used to determine the water consumption of a development. This approach is transparent and compatible with developers’ procurement and the emerging Water Label, which Government and the water companies serving London are supporting.
5.61A Existing homes and workplaces will have to become more water efficient, particularly through metering and water efficiency retrofits. Retrofitting water efficiency measures in existing buildings provides scope for considerable water savings (see Policy 5.4). A rolling programme for the replacement of London’s water mains will reduce wastage and London’s water companies will have to invest in sustainable sources of water. Cooperation will be needed across boundaries to identify and address potential capacity shortfalls of the wider network serving their area. Further detail relating to London’s water and wastewater infrastructure is contained in the Mayor’s Water Strategy.
5.62 The Mayor is committed to explore the concept of ‘water neutrality’ to help to address these issues. The basic premise is that development should not lead to an overall rise in demand for water. The definition of water neutrality used by the Government and the Environment Agency is:
“For every new development, total water use across the wider area after the development must be equal to or less than total water use across the wider area before development.”
The Mayor is working with the water companies to promote in particular demand management measures in their Water Resource Management Plans and Business Plans.
5.63 Alternative sources of water, such as rainwater and greywater, particularly for uses other than drinking, will be increasingly important to reducing our consumption of mains water. It is important to have a positive planning approach to providing a more sustainable and secure water supply infrastructure.
5.64 After major industrial abstractions of groundwater stopped, parts of London (including the Underground, basements and underground services) were at risk of groundwater flooding. This issue has now been addressed with abstractions at additional Thames Water boreholes. It is currently thought that groundwater levels will not be particularly affected by climate change. The position will be monitored, and alterations to the London Plan will be brought forward if necessary.
 Excluding an allowance of 5 litres or less per head per day for external water consumption.
 Environment Agency. State of the Environment Report, February 2013
 Requirement G2 of Schedule 1 to the Building Regulations 2010. HM Government 2015.
 Serious water stress is defined as where current or future household demand for water is – or is likely to be - a high proportion of the effective rainfall to meet that demand. - Environment Agency, Water stressed areas – final classification, July 2013.
 Table 2.2 of Part G of the Building Regulations provides maximum consumption values for water fittings. If these consumption values are exceeded and where waste disposal units, water softeners or water re-use are specified in the application, the Water Efficiency Calculator must be completed.