HCC Climate Change Commission
Water Resources
Water resources in Hampshire are based on groundwater stored in the Chalk
aquifer of the Hampshire Downs and replenished every year by winter rainfall.
This water is exploited directly by the use of wells and boreholes or is
abstracted from the Rivers Test and Itchen, both of which rely on groundwater
to maintain flows.
Historically resilient, this system is now at risk from:
1) increased abstraction associated with population growth, new
development, rising personal consumption,
2) changes to groundwater recharge and river flows caused by climate
change,
3) environmental requirements of designated rivers and wetlands.
Growth in demand
The South East is a densely populated area with low levels of rainfall and the
development proposed in the South East Plan will place greater pressure on
water supplies. Per capita consumption (pcc) rose sharply in the second half
of the 20th century in response to the provision of reliable water supplies and
growing affluence, and people in the south-east now use 150 to 160 litres per
person per day on average, although this is highly variable and tends to peak
in summer.
Climate Change
1. The water resource
Changes in climate have potential impacts on demand and supply. In terms
of water resources, climate change scenarios for central southern England
suggest wetter winters and more frequent summer droughts. Water in
Hampshire is stored in the Chalk aquifer during winter when rain infiltrates the
soil, while summer rain is lost immediately to plant growth and evaporation
(evapotranspiration) and has little impact.
Wetter winters may therefore seem to be favourable to water resources in
Hampshire, but it also appears that winters are becoming shorter. The
recharge season is being squeezed between later and warmer autumns and
earlier springs, so that the opportunity for winter rainfall to recharge the
aquifer is being reduced. In addition, hotter and longer summers are causing
increased evaporation from soils and more plant activity, with an increased
net loss of water from the catchment over the year.
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The end result of these climate change scenarios has been simulated for the
River Itchen using global circulation models and actual river flow and
groundwater data collected in Hampshire over the last 40 years. Predicted
changes in flows in the river at gauging stations near Allbrook in Eastleigh can
be seen in the hydrograph below. Allowing for the inevitably wide bands of
uncertainty, there is still the suggestion that average winter and spring flows
will increase, while flows in summer will fall. High flows in spring are vital for
invertebrate and aquatic plant life, but this ecological benefit would be
balanced against low flows, high water temperatures and peak demand from
society, ie abstraction, during summer. The environmental outcome for
groundwater-fed rivers, as so often with climate change, is still uncertain.
2. Water quality
Lower flows in summer will offer less dilution of effluent from sewage
treatment works and contaminants from diffuse pollution. On the other hand,
heavier rainfall events in winter may cause more soil erosion and runoff from
rural and urban areas. Where the Chalk is in contact with the sea as in
Portsmouth Harbour and along the Sussex coast, sea level rise will bring
more saline intrusion into the aquifer and reduce the amount of freshwater
available.
The nature of the Chalk may change with rising atmospheric CO2
concentrations causing a gradual rise in the acidity of rainfall. Fissures in the
Chalk may widen, allowing more rapid groundwater flows and increased
drainage from natural storage.
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3. Demand for water
There is a positive relationship between ambient temperature and demand for
water based on recreation and hygiene, so it is possible that warmer weather
will tend to drive increased use of water, particularly in summer. This is the
period when water resources are naturally at their lowest and when
continuous low flows, as seen during the droughts of 2005 and 2006, can
damage the water environment.
4. Summary
Examples of direct effects:

Changes in precipitation and evapotranspiration will influence
recharge.

Rising sea levels may lead to increased saline intrusion of coastal and
island aquifers.

Changing CO2 concentrations influence carbonate dissolution and the
formation of karst.

Increased rainfall intensity may lead to more runoff and less recharge.
Examples of indirect effects:

Changes in natural vegetation and crops will influence recharge

Increased flood events may affect groundwater quality in alluvial
aquifers

Changes in soil organic carbon may effect the infiltration properties
above aquifers
Other effects:

Aquifers may naturally store or release greenhouse gases like CO2,
CH4, and N2O.

Aquifers can be used to sequester carbon, such as by storing CO 2
removed from the atmosphere in deep saline aquifers.
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Environment
The development of Catchment Management Abstraction Strategies (CAMS)
across England and Wales has demonstrated the balance between the needs
of abstractors (water companies, industry, agriculture, etc) and those of the
environment (rivers, wetlands, lakes, etc).
The water availability map below shows that there is no significant water
available for further abstraction and that there is already potential damage
under investigation, eg in the lower R Itchen. This map relates to Hampshire
catchments in terms of the Water Framework Directive and excludes the
north-east of the county, including Basingstoke, that drains towards the
Thames valley.
The bulk of the population lives in the coastal conurbation from Totton in the
west to Havant in the east, and the water resources of most of the county are
committed to supplying the PUSH area.
Hampshire enjoys a very wide biodiversity and this sub-region is surrounded
by water-dependent sites designated at national and European level such as
the R Itchen, the New Forest, the natural harbours and estuaries and much of
the coastline. Some water company abstraction licences may need to be
curtailed to protect these sites, in which case alternative supplies will be
developed.
Water Neutrality
The concept of ‘water neutrality’ is therefore becoming more important to
secure water supplies and to protect Hampshire’s high quality environment.
This attempts to maintain total abstraction at a stable level during a period of
development and is achieved by leakage control, demand management and
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water efficiency, the latter being influenced by planning policies and including
retro-fitting of water efficient appliances sin existing houses.
The Code for Sustainable Homes provides a framework for house building
practice including standards for water at 120, 105 and 80 litres pcc. New
town houses and apartments with minimal gardens could be using 130 litres
pcc which is the likely future Building Regulations standard. However, for the
south-east, with growing pressure from planned development, population
growth, risks of more frequent dry summers and a valuable environment to
protect, significantly tighter standards are justified.
The 105 litre standard proposed by PUSH is readily achievable at minimal
cost (in future zero costs as markets develop) by using fittings such as 6/4
litre dual flush WCs, low flow taps and showers and efficient washing
machines that are all currently available. The use of grey water with some
health risks and environmental impacts is not recommended at this time.
Feasibility
Abstraction by water companies peaked in the 1980s and fell sharply in the
early 1990s due to a combination of leakage control, changes in industry, new
technology in water management and building regulations. Annual
abstraction has been fairly stable since then as can be seen in the graph
below showing total water company abstraction. This is despite continued
development and population growth in Hampshire, so it seems that water
neutrality is feasible with further effort on water efficiency.
Hampshire PWS Abstractions 1989 - 2005
150000.00
145000.00
140000.00
135000.00
Ml
130000.00
125000.00
120000.00
115000.00
110000.00
105000.00
100000.00
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
Year
Conclusion
Water efficiency in Hampshire is driven by the needs for reliable water supply
and environmental protection in the face of a changing climate. The 105 litre
standard is achievable at very low cost, will contribute to water neutrality and
has no environmental downside. A consistent standard of 105 litres for new
development across Hampshire will be simple for developers and planning
authorities to implement.
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