Reservoir levels and rainfall figures

Last reviewed:

Rainfall across the Thames catchment was 77.4% of the 131 year historic monthly average, with 40.5 mm from 1 - 31 March.

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 chart April 2016 - March 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 underground boreholes, from which we pump water which has originally fallen as rain and sunk down into the ground. These supplies are referred to as groundwater.

Find out more about where our water comes from

March reservoir and water levels

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

An illustration of reservoir and rainfall levels, March 2017

Water situation summary March 2017

  • Groundwater levels at most boreholes are slightly below normal, although they are still increasing (except for the Cotswolds, which have started decreasing).
  • On 31 March, the Thames Regional Soil Moisture Deficit (SMD) total was 14mm which is slightly drier than the expected 10mm.
  • Most river flows were still below their long term averages in March. The Teddington Target Flow remained at 800 megalitres/day during the month in agreement with the the Environment Agency. 
  • Reservoir storage on the 31 March 2017 for London as a whole was 95% (Thames Valley 98% & Lee Valley 83%) and Farmoor storage was 96%.