From 1-31 May, rainfall across the Thames catchment was 109% of the 134 year historic monthly average, with 59.9mm.
Rainfall in the last year
The graph below shows the rainfall over the last year and percentage increase and decrease against the monthly average.
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.
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 summary
On 31st May 2018, the Thames Regional Soil Moisture Deficit (SMD) total was 41mm which is lower (i.e. wetter) than expected for the time of year.
At the end of May, groundwater levels were generally Normal to Above Normal, with some exceptions. An area of the Chilterns and the Guildford Lower Greensands were Below Normal, whereas an area of the Marlborough Downs was Notably High.
Generally, river flows were at their long term averages in May. The Teddington Target Flow was maintained at 800 megalitres/day during May in agreement with the Environment Agency.
Reservoir storage on the 31st May 2018 for London as a whole was 97% (Thames Valley 98% & Lee Valley 94%) and Farmoor storage was 98%.