It may be raining, but will there be a summer water shortage? Latest reports from @SESWater ‏and @thameswater ‏

In April SES Water updated their report on the current state of water levels in their area. Officially the South East is classified as being in “serious water stress” due to the imbalance between water supply and water demand.

Below is a graph of rainfall in the SES Water area from April 2016 to March 2017.

Source: SES Water (

More importantly, the graph below shows the same period (for Thames Water), but as a variance between the rain that actually fell and what we would expect as normal. June 2016 was very wet but July, August, October, December, February and March were all exceptionally dry.

Rainfall Chart May 2016 - April 2017

Source: Thames Water (

SES Water state that they are “not currently planning any water supply restrictions this summer”, but the Met Office has issued a long-range weather forecast of “above average temperatures and below average rainfall”

According to Thames Water 65% of the water that we all use here in Chessington comes from rivers, the water is extracted, stored and treated before turning it in to drinking grade water. The remaining 35% comes from “ground water” via boreholes.

Thames Water have provided a fantastic graphic to illustrate how we get our water and the current state of our supplies.

An illustration of reservoir and rainfall levels, March 2017

Source: Thames Water (

From the Thames Water graphic, all supply sources are “Below average”, key to this situation is that rainfall is at 77.4% of expected levels. As of March 2017 Thames water have given the following statements:-

  • Groundwater levels at most boreholes are slightly below normal, although they are still increasing (except for the Cotswolds, which have started decreasing).
  • On 31 March, the Thames Regional Soil Moisture Deficit (SMD) total was 14mm which is slightly drier than the expected 10mm.
  • Most river flows were still below their long term averages in March. The Teddington Target Flow remained at 800 megalitres/day during the month in agreement with the the Environment Agency.
  • Reservoir storage on the 31 March 2017 for London as a whole was 95% (Thames Valley 98% & Lee Valley 83%) and Farmoor storage was 96%.

By @HortonWeather


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