Reservoir levels and rainfall figures

Last reviewed:

From 1-30 June, rainfall across the Thames catchment was 5% of the 134 year historic monthly average, with 2.5mm.

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 30th June, the Thames Regional Soil Moisture Deficit (SMD) total was 92mm which is higher (i.e. drier) than expected for the time of year.

At the end of June, groundwater levels were generally Normal, with some exceptions. An area of the Lee Chalk in North East London and an area of the Guildford Lower Greensands were Below Normal, whereas an area of the Cotswolds and an area of Marlborough Downs were Above Normal.

Generally, river flows were at their long term averages in June. The Teddington Target Flow was maintained at 800 megalitres/day during June in agreement with the Environment Agency. Although since 06 July 2018 the Teddington

Target Flow has changed to 700 megalitres/day in agreement with the Environment Agency.

Reservoir storage on the 30th June 2018 for London as a whole was 93% (Thames Valley 96% & Lee Valley 87%) and Farmoor storage was 95%.