Did you know that in times of dry weather, when groundwater levels drop, the top of the Wandle in Carshalton is kept flowing artificially?
We all need water to drink and wash, and in Carshalton, at the top of the Wandle, the water in our homes is provided by SES Water (who have recently changed their name from Sutton and East Surrey Water Company).
The water that comes out of our taps is the same water that springs out of the chalky geology of the North Downs as the source of the River Wandle. SES Water has a licence to abstract some of this water from the chalk aquifer and supply it to us for domestic use. But as part of this licence, they also have to ensure there is enough water in the River Wandle (because there are lots of species of insects, birds and fish in the river which need flowing water).
To do this when the aquifer is low and the springs are not flowing (usually in late summer), SES turns on an artificial recirculation system which pumps water from the Wandle just north of Goat Bridge up to Carshalton Ponds, where it replenishes the Carshalton arm of the river. Without this system, the Carshalton arm of the Wandle would be dry for much of the year.
As you may have noticed, Carshalton Ponds have been getting drier recently. We think this is because there are some cracks in the edges and bottom of the Ponds, which mean that when SES Water pump water into the Ponds, it seeps back into the ground before it can get out of the lower Pond and flow down the Wandle. This is causing SES Water to fail their licence requirements to keep the Wandle flowing, so at present they need to pump most of the water straight into the river below the cascade in Grove Park, with a small flow to the Ponds to top them up.
SES Water, the Environment Agency (EA) and Sutton Council are now working together to plan and deliver restorative works to the ponds and rectify the issue as soon as possible.
In the meantime, we can all do our bit by trying to save water. Look out for our exhibition coming up in Sutton Library (July 2017) where you can learn more about the past and present sources of the river, and simple actions we can all take to save water and help the Wandle.
Update: The Council were able to make repairs to the ponds and Sutton and East Surrey Water started pumping water back into the ponds on Sunday 9th April.