Reservoir levels and rainfall figures

Last reviewed:
From 1-31 May, rainfall across the Thames catchment was 122% of the 131 year historic monthly average, with 66.7 mm.

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 graph up to May 2017

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

May 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.

May 2017 Water Resources Picture

May 2017 Water situation summary

  • Groundwater levels are below normal.
  • On 31 May, the Thames Regional Soil Moisture Deficit (SMD) total was 71mm which is drier than the 53mm expected for the time of year.
  • Most river flows were below their long term averages in May, aside from after a few periods of heavy rainfall. The Teddington Target Flow remained at 800 megalitres/day during the month in agreement with the the Environment Agency. 
  • Reservoir storage on the 31 May 2017 for London as a whole was 97% (Thames Valley 98% & Lee Valley 92%) and Farmoor storage was 97%.