Research and analysis

Groundwater situation: Hampshire 18 December 2024

Updated 19 December 2024

Current situation

Groundwater levels in Hampshire are high and continue to rise in response to a wet autumn. However, December 2024 has been slightly drier than normal so far, with all locations in the county recording between 25mm and 50mm of rain. Because of this, the rate at which groundwater levels are rising has been slowing down.

Groundwater flooding impacts in Preston Candover and Old Alresford are imminent. In other susceptible communities in north, west and central Hampshire, impacts could begin in late-December or early in the New Year. Impacts could include:

• winterbourne streams flowing
• flooding to land, roads and cellars
• the inundation of sewerage systems and septic tanks

Flood water on the road may cause icy conditions during spells of cold weather.

Figure 1: Graph showing changes in groundwater levels in Clanville Gate Borehole in North Hampshire from December 2022 to December 2024. The graph shows groundwater levels rising from the beginning to October 2024 until now. Groundwater levels are very high for this time of year and continue to rise.

Figure 2: Graph showing changes in groundwater levels in Hursley Borehole in central Hampshire from December 2022 to December 2024. The graph shows a steep incline in groundwater level from the beginning of October 2024. Groundwater levels are currently high, and continue to rise quickly.

Figure 3: Graph showing changes in groundwater levels in Whitedale Farm Borehole in East Hampshire from December 2022 to December 2024. The graph shows a steady incline in groundwater level from the beginning of October 2024. Groundwater levels are average for this time of year and rising steadily.

Weather forecast

Over the next 5 days, rain and showers are expected to affect Hampshire. If heavy rain affects the area, then the rate at which groundwater levels are rising will begin to speed up. From Monday 23 December 2024 to Friday 27 December 2024, dry weather is expected to be the dominant pattern, although there may be spells of rain or showers at times. Groundwater levels in Hampshire are generally expected to keep rising for most of December in response to this week’s rainfall.

Long range forecasting is difficult. Currently there is a suggestion that, while some unsettled weather is likely at times, the rest of December and beginning of January is expected to be drier overall with a greater influence of high pressure. Groundwater levels would begin to stabilise if drier weather conditions occur.

Forecast risk of flooding

If very heavy rain does affect Hampshire in the next couple of weeks, then it is possible that groundwater flooding effects, such as cellar flooding, road flooding, and inundation of septic tanks and sewerage networks, could occur before the end of December or in early January. The communities most at risk of groundwater flooding effects within the coming weeks are villages surrounding Andover, Deane and Ashe, the Bourne Valley, Hursley, the Wallops, Broughton and West Tytherley. If heavy rain occurs over the coming months, then all susceptible locations in Hampshire could experience effects from flooding during this winter.

If we record an average total of rain this winter, then it is still likely that groundwater flooding effects will occur in a small number of susceptible locations in north and central Hampshire. Generally, it would require a much drier than average winter for the effects of flooding to be avoided everywhere this year. As ever, the impact from rising groundwater levels will vary, depending on the exact amount, intensity, and location of rainfall over the next few months.

Next update

We will update this groundwater situation document by Friday 17 January 2025. When in force, groundwater Flood Alerts are updated with information more frequently.

What the Environment Agency are doing

• We continue to monitor groundwater levels and their response to rainfall. 
• Throughout autumn and winter, we will update this groundwater situation document 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 make sure they are aware of the situation. 
• Environment Agency operational staff will remove blockages from main rivers, to make sure they flow freely.

Actions and advice

Think and prepare now for what you will do if flooding occurs where you live, do not 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. Move valuables 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 to register your email address.

Contact

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, for more information, you can contact: 

• 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