How much rain falls in our region?

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 region

In February, we saw above average rainfall in the Thames Region. At 123.2 mm, it was 238% of the long-term average.

On 29 February, the Thames Regional Soil Moisture Deficit (SMD) total was 0 mm, meaning that the ground is saturated. This indicates that the soil is slightly wetter than expected for this time of year.

Groundwater levels were generally above average across the Thames region by the end of February; with levels in an area of Hertfordshire below average.


Average rainfall in the Thames region

Check out our graph to see average rainfall for the Thames region:

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 the Thames region

During February 2020, river flows were generally above average across the Thames region. However, flows in the River Lee were often below average during February, peaking above average with significant rainfall. This means that in most areas there has been more water in our rivers than expected for the time of year.

The Teddington Target Flow (TTF) was maintained at 800 Ml/d during February. 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 February 2020:

  • Reservoirs in London were 94% full (94% full in West London and 95% full in Lee Valley)
  • Farmoor Reservoir in Oxfordshire was 97% full

Our water resources situation

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

Reservoir and rainfall diagram

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