Our water resources

HomeOur water resources

Our water resources

Where our water comes from
The geology of the region means much of our water (85%) comes from underground.

When it rains, water runs into streams and rivers and soaks into the ground. In spring and summer, much of it evaporates or is used by plants and trees. In winter, the rain seeps into the topsoil and into the rock beneath the surface. This water-holding rock, or aquifer, acts like a giant sponge, holding the groundwater within it.

The rock is either chalk or greensand and we abstract water using boreholes sunk at a depth of between 90m - 180m. The water is pumped to the surface, and then piped to our treatment works. We have 7 works which treat groundwater supplies; in Cheam, Woodmansterne, Kenley, Leatherhead, Reigate, Godstone and Oxted.

The rest of our water (15%) comes from our reservoir at Bough Beech, near Edenbridge, which is filled from the River Eden in Kent, during the autumn and winter.

How our water is treated
Water from boreholes is of high quality, because the chalk and greensand acts as a natural filter. However, it still needs to be purified before it is safe to drink. We further improve the quality of the water by a treatment process called 'softening'.

The water extracted from our boreholes is known as 'temporary' hard water. That means that it contains dissolved minerals, mainly calcium and magnesium bicarbonates, which produce a 'scum' when mixed with soaps and detergents. Also, when hard water is heated, a solid precipitate called 'scale' is produced.

Softening makes the water much more pleasant to use and reduces the amount of soap and other detergents needed. It also reduces scaling in tanks, boilers and kettles. Softening therefore keeps household costs down and helps the environment.

River water needs a different type of treatment process. In general, it needs more filtration and treatment to remove substances which cause taste and smell.

Rainfall data

SES Water and its predecessors have been recording data on the amount of rainfall since 1910. See our rainfall and resources page to find out more.

View rainfall

Water Resources in the South East Group (WRSE) is a sector-wide partnership that, every five years, develops a south east strategy for water.

The group is working together to look 60 years ahead to find better or new ways of sharing water - using existing sources, pipes and treatment works or developing new sources of water and bigger, longer pipelines to move it further. 

Find out more . . .