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.


Groundwater levels in our Central region remain in drought zone 2, just above the drought zone 3 trigger level. They have continued to decline since last month. This is despite relatively high rainfall in June which was 166% of LTA in Central region. This continued decline follows the LTA trend as on average, warmer temperatures and higher soil moisture deficit (SMD) through the summer mean that less rainfall percolates down through the soil to recharge the aquifers. If they follow the LTA trend, groundwater levels will continue to decline until autumn/winter 2019.

Groundwater levels are likely to reach drought zone 3 this year, and under most rainfall scenarios (i.e. 120% of LTA rainfall or less) this is likely to be in August. The rainfall over the coming months will determine the rate and extent of groundwater recession, with autumn rainfall and SMD being key to determine the start of the next recharge season. Low rainfall (60% or 80% of the LTA) may result in levels failing to recover out of the drought zone, representing an elevated risk for next year.