Reservoir levels and rainfall figures

Last reviewed:

From 1-31 December, rainfall across the Thames catchment was 125% of the 131 year historic monthly average, with 94.5mm.

Rainfall in the last year

The graph below shows the rainfall over the last year and percentage increase and decrease against the monthly average.

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

Where our water comes from

Across our region, we take about 65 per cent of our source water from rivers, in a process called abstraction. We then store this in large, open reservoirs (known as surface reservoirs) before putting it through our treatment process to turn it into drinking water.

The remaining 35 per cent comes from natural underground reservoirs called aquifers, from which we pump water using boreholes. This water has originally fallen as rain and sunk down into the ground in a process called recharge. These supplies from aquifers are referred to as groundwater.

Find out more about where our water comes from

Reservoir and water levels

The diagram below shows the rainfall and levels of water in the rivers, aquifers and reservoirs in our area, for the last month.

Reservoir and rainfall diagram

Water situation summary

On 31st December 2017, the Thames Regional Soil Moisture Deficit (SMD) total was 1mm, for the time of year we would expect 3mm.

At the end of December, groundwater levels are showing signs of recovery. However, groundwater levels generally remain Below Normal or Notably Low for the time of year, with the exception of the Cotswolds where groundwater levels are Normal to Exceptionally High.

River flows were generally below their long term averages during December.

Reservoir storage on the 31st December 2017 for London as a whole was 76% (Thames Valley 75% & Lee Valley 81%) and Farmoor storage was 95%.