Carshalton stands on the spring line at the foot of the North Downs, and once contained numerous springs and watercourses. Some of these, such as the ponds and the grotto canal and the Hogpit which used to be used as a reservoir of water for the High Street Mill, survive today and are significant elements of the landscape.
In the 1920s Carshalton Urban District Council bought The Grove and turned it into a public park. They also bought up the properties around the ponds to preserve the character of the area. This campaign was successful and the ponds area retains much of its historic character to this day. A spring named Margaret’s Pool is located at the corner of West Street and Pound Street. It is now generally dry but in the 19th Century it flowed regularly and was cleaned and ornamented at the expense of John Ruskin, who asked that it be called Margaret’s Pool after his mother.
The underlying rocks in the area are chalk. Chalk is porous and soaks up rain like a sponge, storing it in the rock as groundwater. Winter rain falling on the North Downs gradually percolates through the chalk and tops the groundwater levels up - usually at it's highest in spring after the winter rain. As the groundwater levels rise, the water emerges as springs where the chalk meets the London Clay and begin to flow all around the area – but only when the rainfall is well above average. One reason for the springs not appearing is the fact that there is so much water extraction from the area by the water companies.
As groundwater levels fall through the late spring and summer, the springs dry up and the streams will stop flowing. The groundwater doesn't get much of a top up in the summer, even if it rains a lot, as vegetation and water evaporation mean that little rainfall soaks through to the chalk.
During this winter 2013/2014 there were 20 inches of rain between November and January and all of the springs began to flow and Carshalton could be seen in all it’s former glory. Once the water begins it continues for many months as the water percolates from the North Downs.
To claim this Earthcache please send us an e-mail with the answer to the following 4 questions.
1. How deep is the water in front of the Grotto, if any?
2. Go down the steps and look at the brick wall. There are some large stones at ground level on the right section of wall which are remains of the original decoration of The Grotto. What type of stones are these and how are they formed?
Then walk along the Grotto canal, cross Ruskin Road and walk down past the cascade towards the High Street.
3. Turn left and walk west along the High Street, past the first of the ponds then walk behind the second pond to Festival Walk where you will find another seasonal stream and Margaret’s Pool. How deep is the water in this stream?
4. In the last few decades the flow in the Spring months has not been seen as often as in historical times. Email the cache owner with a reason why the water table may not be reaching up as high as it used to. There could be several reasons for this.
As an optional extra please add a photo showing the water.
There is plenty of free parking in the surrounding streets. Please note that Carshalton Park is due to be locked at dusk each day
Whilst in the area there are quite a few other local caches including our three Church Micros.
Please send your answers before you log the Earthcache.