Serving parts of North West London and the Home Counties.

Groundwater levels

Central Region


Central region water levels hydrograph

*The long term average (LTA) has been calculated statistically, using the long term data record for this hydrograph. The respective drought zones are used as operational triggers, and have been derived using the LTA.


Rainfall in August was 77% of the LTA. The rainfall pattern this spring and summer has been variable, with June and July experiencing above average rainfall but with lower rainfall in April and May. During the summer months, warmer temperatures and higher soil moisture deficit (SMD) mean that less rainfall percolates down through the soil to recharge the aquifers. Consequently, Chalk groundwater recovery is mainly driven by winter rainfall. Levels have continued to decline in our Central region at a similar rate to the LTA and are currently in drought zone 3, below August 2017 levels.

The rainfall and temperature conditions over the autumn/winter period will determine the timing and extent of groundwater level recovery. Low or very low rainfall (60% or 80% of the LTA) may result in levels similar to those seen in December 1997, and an increased risk position for next year. Continued above average rainfall, especially over the autumn and winter months, will be required for an improvement in the outlook for groundwater levels in our Central region next spring.