Groundwater levels
The clean water that flows out of your taps comes from natural underground stores. Heavy or continued rainfall causes these underground stores to overfill. With nowhere else to go, groundwater rises.
- Groundwater levels rise and fall each year depending on rainfall accumulation. They generally rise in winter and spring then fall in summer and early autumn.
- High groundwater levels can lead to increases in the flow within our sewers. In extreme conditions, our sewers can become overloaded and flood.
- Groundwater is an essential part of supporting healthy river flows. This is particularly important during the summer months.
Latest groundwater levels
The Environment Agency monitor groundwater levels at several observation boreholes across our region. We use the data to understand the risk to our system. This enables us to target operations quickly to reduce the impact.
Groundwater levels were exceptionally high in Swindon and Oxfordshire at the end of February 2026. They were mostly normal across the rest of the region.
You can view all groundwater levels on GOV.UK.
The groundwater situation document covers a range of sites across the South East. Key sites in the Swindon and Oxfordshire area are Jackaments Bottom, Stonor Park and Rockley.
Rainfall
In February, we experienced above average rainfall in the Thames Catchment. At 107mm, it was 206% of the long-term average.
The graph shows how rainfall differs from the long-term average for the Thames catchment.
Current groundwater flooding incidents
Find out more about the work we're doing to prevent groundwater flooding in some of the worst-affected areas.