Research and analysis

Groundwater situation: Hampshire 6 June 2024

Updated 6 June 2024

Current situation

Groundwater levels in Hampshire remain higher than normal for this time of year, but are slowly falling. In May 2024, average or above average rainfall was recorded across Hampshire, with all of our rain gauges receiving between 90% to 230% of the long-term average for this month. Almost no rain has been recorded during the first week of June.

As we move into the summer months, groundwater levels will continue to fall across the county. A small amount of flooding impacts continue in the North-West Hampshire. Impacts include flooding to a small number of cellars, as well minor impacts to sewerage networks and septic tanks.

Figure 1: Graph showing changes in groundwater levels in Oakley Borehole in North Hampshire from March 2022 to May 2024. The graph shows a steep incline in groundwater level from the end of October 2023 to the middle of January 2024. The level then remains stable until mid-February 2024, before another incline in groundwater level until mid-March 2024. Groundwater levels have been steadily declining since then.

Figure 2: Graph showing changes in groundwater levels in Hursley Borehole in central Hampshire from January 2022 to March 2024. The graph shows a steep incline in groundwater level from the end of October 2023 to mid-January 2024. The level then slowly declines until early-February 2024. The graph then shows another incline in groundwater level until mid-March 2024. Groundwater levels have been steadily declining since then.

Figure 3: Graph showing changes in groundwater levels in Whitedale Farm Borehole in East Hampshire from January 2022 to March 2024. The graph shows a steep incline in groundwater level from the end of October 2023 and a steep decline during January 2024. From mid-February 2024, the graph shows another steep incline in groundwater level until mid-March. Groundwater levels have generally been declining since then.

Forecast risk of flooding

In the spring and summer months, groundwater levels are expected to continue falling as we expect less rain, warmer weather and more plant growth.

Long range forecasting is difficult. Over the next 10 days, mostly dry weather is forecast in Hampshire and groundwater levels are expected to continue falling slowly. Ongoing isolated groundwater flooding impacts to cellars will continue through much of June. Minor sewerage system impacts may continue into July. All groundwater flooding impacts are expected to have fully receded within the next 6 weeks.

Groundwater levels in all susceptible locations are high for this time of year and will likely be higher than average when approaching the next winter season. We recommend that residents review flood plans and check flood protection equipment as there is an increased risk of groundwater flooding impacts next year.

Next update

With groundwater levels expected to continue to fall, and flood risk reducing, we are not planning to update this briefing note next month. However, we will continue to monitor the levels and forecasts and will re-issue this briefing note at any time when new instances of groundwater flooding are thought possible. We will likely re-issue this briefing note in autumn or winter 2024.

What we are doing

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

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

We will remove flood alerts when no further flood risk is expected.

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

Our operational staff removing 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
• groundwater situation information for North Hampshire (Alton, Basingstoke, Crondall, Farringdon, Sherborne St John)
• 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