London scoping - ukcip

Final Report
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set to build nearly 500,000 new houses over the next fifteen years. The draft London Plan has
proposed that a half of these should be ‘affordable’ housing. These houses will have to be
designed and constructed with climate change in mind; existing housing stock may also have to
be adapted to cope with increased summer temperatures, more winter rainfall and, arguably,
more extreme weather events. Already we are seeing air conditioning being used in the
domestic sector, and this trend is likely to continue given projections of climate change.
6.8.2 Changes in rainfall and water resources
Water shortages in the summer could result in more frequent non-essential use water restrictions
which would affect households which have got used to abundant water supplies. It might be
supposed that London would have a lower per capita water consumption than the UK average,
because gardens in London are probably smaller. Somewhat surprisingly, however, the per
capita consumption of water in London is actually higher than the UK average (155 litres per
head per day compared to the national average of 146 litres per day). The reasons for this
appear to be two-fold:
Greater affluence in London leads to higher levels of ownership of water
consuming devices (washing machines, dishwashers, power showers, etc.)
The lower household size in London relative to the UK as a whole (as occupancy
levels decrease, per capita water consumption increases). (Tattersall, Thames
Water, pers.com.).
Without behavioural change, household demand for water in a hotter climate would increase
due to more clothes washing, more showers, more water for gardens and so on. Lack of water
for irrigation of parks and gardens, and for street cleaning would have an adverse effect upon
the image of London, especially for visitors. It is likely that that non essential use restrictions
would be imposed to manage a drought situation, with the introduction of rota cuts and
standpipes being a last resort measure with a range of demand management measures being
introduced between these two extremes.
The five Water Companies that supply London are Thames Water, Three Valleys, North Surrey,
Essex and Suffolk and Sutton and East Surrey Water. Thames Water is the largest supplier of
water and has a well distributed groundwater resources and the major surface water resources,
all of which is managed as an integrated system (ibid.). Groundwater storage is used to
compensate in part for the lack of rainfall over a number of seasons. Thames Water also has the
advantage that it is abstracting water for London close to the tidal interface, which means that it
can extract more water for public supplies (DeGaris, pers.com.). However the utilisation of this
source has a number of issues including navigation, tideway water quality and ecology. Three
Valleys relies largely on groundwater sources though does have surface water source from the
Thames near Iver. They also import water from Grafham reservoir in Anglian Region. Thames
Water is the only water supplier with large reservoir storage facilities within Thames Valley
basin. These reservoirs allow greater resilience and there were no drought orders in the Thames
Region in 1995. Reservoir storage was, however, falling at 1% per day in the 1995 drought, so
it cannot be claimed that London’s water supply system is 100% robust in a single year drought
event (ibid.). Resource stress would, therefore, only be apparent over a longer period of low
rainfall, e.g. extending over at least two winters (March, pers.com.). Water stress might also
increase as a result of increasing demand for water from the environment. The benefits of