Reservoir levels and rainfall figures

Last reviewed:
From 1-30 September, rainfall across the Thames catchment was 102% of the 131 year historic monthly average, with 60.6mm.

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

September 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.

Water situation during September

October 2017 Water Situation Summary

  • Groundwater levels are generally Below Normal to Notably Low for the time of year at all locations apart from an area of the Cotswolds, which remains Normal and an area of the Chilterns where levels are Exceptionally Low.
  • On 3 October, the Thames Regional Soil Moisture Deficit (SMD) total was 93mm which is drier than the 80mm expected for the time of year.
  • River flows were generally a little below their long term averages in September, with a few significantly below their long term averages. The Teddington Target Flow was maintained at 700 megalitres/day during the month in agreement with the the Environment Agency. 
  • Reservoir storage on the 5th October 2017 for London as a whole was 69% (Thames Valley 67% & Lee Valley 82%) and Farmoor storage was 94%.