Serving parts of North West London and the Home Counties.

Groundwater Levels

South East Region


South East 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.

*Drought zone 1 is the LTA in South East region.


Groundwater levels are currently just below the drought zone 1/LTA curve, having seen a substantial recovery during December 2018 but a reduced rate of recovery through January. They started the 2018 recession period above the LTA but the hot dry summer caused a decreasing trend which was slightly steeper than the LTA and allowed levels to dip briefly into drought zone 1. Soil moisture deficit (SMD) was higher than the LTA from June until November 2018 (higher than average SMD decreases the recharge component from rain, as more water is absorbed by the soil). November and December rainfall (over 130 % of the LTA for both months) eroded this and prompted the groundwater recovery which was seen during December 2018. January rainfall was low (40 % of the LTA) and caused a slight increase in the SMD and decreased the rate of groundwater level recovery.

The increase in groundwater levels is expected to continue until late March 2019, if the trend follows the LTA. A range of scenarios for 2019 are possible. Average rainfall (100 % of the LTA) would see levels track slightly below the LTA trend during the seasonal recession. Less rainfall (80 % or 60 % of the LTA) could see levels approach drought zone 2 in the summer or autumn of 2019 respectively.