Research and analysis

Groundwater situation: Sussex, 19 January 2026

Updated 20 January 2026

Applies to England

Current situation

Less rain than average was recorded in spring and summer 2025. Autumn was wetter than average, with particularly wet periods during the first half of September and the second half of October 2025. The first half of December 2025 was also wet, but other than the 18 December 2025 the end of the year was characterised by cold and dry days. 2026 began cold and dry too, but in the second week of January persistent widespread rainfall occurred.

With only small amounts of rain through spring and summer, groundwater levels fell and remained low through autumn. Following December’s persistent rain, groundwater rose, but stabilised during the cold end of the year. January’s rain caused groundwater to rise again. At most monitoring boreholes in Sussex, groundwater is now at an average level for the time of year. A few boreholes, including Chilgrove near Chichester, and Houndean near Lewes are higher than average for the time of year.

Groundwater flood impacts are not thought to be occurring.

Graph showing changes in groundwater levels in Compton Borehole in West Sussex from November 2023 to January 2026. The graph shows that groundwater levels are currently average for the time of year and currently rising.

Graph showing changes in groundwater levels in Ladies Mile Borehole near Brighton from November 2023 to January 2026. The graph shows that groundwater levels are currently average for the time of year and currently rising.

Weather forecast

Periods of rain are forecast on each of the next 5 days, to 23 January 2026. There remains uncertainty in locations and amounts, but it could be possible for some locations in Sussex to receive the equivalent of another half a month’s rainfall over the coming week.

More unsettled weather is predicted during the last week of January 2026, but there is uncertainty in geographic location. The unsettled weather might predominantly affect the west of England. Longer term weather forecasting is very difficult, but the current suggestion is that February could start with colder weather, although with milder and wetter weather possible again from the middle of February 2026.

Forecast risk of flooding

Most boreholes are expected to show an initial slowing of their groundwater rise around 21 January 2026. However, if persistent and widespread rainfall occurs this week, groundwater would rise again. If further rain were to also occur during the last week of the month, groundwater would probably rise through to the end of January 2026, when there could be the potential of some minor groundwater flood impacts to occur in a few communities. Including on the Lavant valley near Chichester, the Ems Valley near Stoughton and Walderton, and in Denton, near Newhaven. Impacts could include springs appearing, small amounts of water flowing in fields, gardens, on roads, and potentially basements of isolated properties affected. In Patcham, with groundwater levels still relatively low, groundwater flood impacts are thought less likely.

In most years, most boreholes experience groundwater rise until March. Groundwater risk could continue or increase through February 2026.

It is very difficult to accurately predict the weather weeks or months ahead, and the forecast might change. The exact groundwater response will depend on the amount, intensity and distribution of any rainfall that occurs.

If only a small amount of rain occurs this week, and a period of cold weather occurs in February, then groundwater flood impacts will probably not occur this winter. Not before late February / March, at the earliest.

Next update

We will update this groundwater situation document by Friday 30 January 2026, or sooner if the risk of flooding significantly increases.

When in force, groundwater flood alerts are updated with information more frequently.

What we are doing

We continue to monitor groundwater levels and their response to rainfall.

Throughout autumn and winter, we will update this groundwater situation and our groundwater briefing notes.

We will issue and update flood alerts when there is risk of flooding affecting property.

We liaise with the local authority and other responding partners to ensure they are aware of the situation.

Our operational staff will remove blockages from main rivers, to ensure they flow freely.

Actions and advice

Think and prepare now for what you’ll do if flooding occurs where you live, don’t wait until flooding happens.

Call Floodline on 0345 988 118 or visit check for flooding to find out if you can register to receive free flood alerts for flooding from groundwater.

Look for data in your area:

• groundwater data
• river, sea, groundwater and rainfall levels

There is practical advice on what to do before, during and after groundwater flooding, and further guidance about groundwater flooding, how it might affect you and what to do.

Prepare a personal flood plan or community flood plan to help you and your community decide what practical actions to take before and during a flood, which will help reduce the damage flooding could cause.

Check pumps and any other flood protection equipment you have. Ensure valuables are moved from basements and other low parts of properties.

Where safe to do so, communities may wish to check and ensure there are no blockages in local watercourses and ditches.

Further information

You can view:

• daily groundwater levels compared to average and maximum, with indicative impact thresholds
• sub daily groundwater levels on Gaugemap
• the latest flood alert information
• water situation reports

More detailed groundwater briefing notes are emailed as part of the flood alert service. See contacts section below to register your email address.

Contacts

For more information on the flood alert service and to find out what messages you are registered to receive, call Floodline on 0345 988 118.

Alternatively, you can contact the following for additional information:

• Environment Agency Customers and Engagement: ssdenquiries@environment-agency.gov.uk
• Environment Agency Incident Reporting Hotline: 0800 807060
• Environment Agency National Customer Contact Centre: 03708 506 506