How much rain falls in our region?

Last reviewed:

It may feel like it rains a lot in the UK, but did you know that our capital city gets less rain each year than Rome, Istanbul and even sunny Sydney?


The latest news on average rainfall and groundwater levels in the Thames area

In August, we saw below average rainfall in the Thames Region. At 53.1 mm, it was only 83% of the long term average. The rainfall varied significantly across the region, with the Cotswolds receiving 106% and the Chilterns receiving 68% of their respective long term averages.

On 31 August, the Thames Regional Soil Moisture Deficit (SMD) total was 112mm, indicating that the soil is drier than expected for this time of year.

Groundwater levels in the UK were generally below average during August, except for areas of the Cotswolds where groundwater levels were average. Significant groundwater recharge will not begin until the SMD reduces, usually late autumn/winter.


Average rainfall in the Thames area

Check out our graph to see average rainfall in our region for this year so far:

Rainfall percentages for the last 12 months in relation to long term average rainfall

Where water comes from

We rely on rain to maintain groundwater levels in our region.

Groundwater is the water that soaks into our natural underground reservoirs called aquifers. These supply up to 30% of the water we use every day across London and the Thames Valley. But that’s not all our aquifers do – they also help to keep our rivers flowing, which is where the remaining 70% of our water supply comes from.


River flow in South East England

In August 2019, many of our rivers experienced below average river flows, meaning that there was less water in our rivers than expected for the time of year.

The Teddington Target Flow (TTF) was 700 Ml/d during August. The TTF is the minimum River Thames flow over the Teddington weir that is required to balance environmental, navigational and water supply needs. The TTF depends on the time of year and our reservoir storage, and is always agreed with the Environment Agency.


Saving for a rainy day

We store water in large, open raw water reservoirs before we pump it to our world-class treatment plants, ready for cleaning.

We carefully monitor water levels in reservoirs, regularly inspecting and maintaining the infrastructure to safeguard your supply.

At the end of August 2019:

  • Reservoirs in London were 75% full (74% full in West London and 84% full in Lee Valley)
  • Farmoor Reservoir in Oxfordshire was 96% full

Our water resources situation

Check out our infographic to see our water resource situation at the end of August:

Reservoir and rainfall diagram

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