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 December, we saw above average rainfall in the Thames Region. At 109.5 mm, it was 146% of the long-term average.

On 31 December, 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 average to above average across the Thames region by the end of December; with levels in Hertfordshire below average.


Average rainfall in the Thames region

Check out our graph to see average rainfall in our 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 our region

By the end of December 2019, river flows were generally above average across the Thames region, with flows in the River Lee and other smaller rivers below average during the beginning of the month, increasing to above average by then end of the month. 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 December. 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 December 2019:

  • Reservoirs in London were 91% full (92% full in West London and 87% full in Lee Valley)
  • Farmoor Reservoir in Oxfordshire was 99% full

Our water resources situation

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

Reservoir and rainfall diagram

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