Reservoir levels and rainfall figures

Last reviewed:

From 1-30 September, rainfall across the Thames catchment was 62% of the 134 year historic monthly average, with 36.9mm.

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 September, the Thames Regional Soil Moisture Deficit (SMD) total was 123 mm which is higher (i.e. drier) than expected for the time of year.

At the end of September, groundwater levels were generally average to below average.

Generally, river flows were below their long term averages in September. The Teddington Target Flow which determines the minimum flow that must be maintained over Teddington weir, was maintained at 700 megalitres/day in agreement with the Environment Agency.

Reservoir storage on the 30th September 2018 for London as a whole was 62% (West London 60% & Lee Valley 74%) and Farmoor storage was 90%.