Winter Groundwater Monitoring: Why planning should start now

Winter may still feel some way off, but groundwater monitoring cannot always be arranged at short notice. 

Before monitoring begins, time is needed to review the site, confirm the scope, allocate budget, appoint an engineer and install suitable monitoring wells. Leaving these steps until the wetter months have arrived could mean missing part of the required monitoring period. 

For developments where seasonal groundwater levels may affect drainage, infiltration or below-ground design, now is the time to start planning.

Why Monitor Groundwater During Winter? 

Groundwater levels can change throughout the year in response to rainfall, evaporation and local hydrogeological conditions. Levels are often higher during the wetter months, when increased rainfall and reduced evaporation contribute to groundwater recharge. 

A groundwater reading taken during a single site visit only represents conditions at that particular moment. Monitoring over an appropriate period provides a clearer understanding of how groundwater behaves across the site and helps establish the seasonal conditions that need to be considered during design. 

This information may be required to support: 

• Surface water drainage and Sustainable Drainage Systems (SuDS) design 
• Infiltration systems and soakaways 
• BRE 365 infiltration testing 
• Basement and below-ground structure design 
• Site layouts and development plans 
• Flood risk and hydrogeological assessments 
• Planning applications and the discharge of planning conditions 

Identifying groundwater constraints before designs are finalised can reduce uncertainty and help avoid delays or costly changes later in the project. 

Why Does Planning Need to Start Now? 

Some groundwater monitoring programmes may need to run for several months or cover a full seasonal cycle. The appropriate duration will depend on the site, proposed development, hydrogeological conditions and requirements of the relevant authority. 

Before data collection can begin, the following may need to be completed: 

• Review of existing geological and hydrogeological information 
• Confirmation of planning or drainage requirements 
• Preparation and approval of the monitoring scope 
• Allocation of project budget 
• Appointment of a suitably qualified consultant 
• Site access and utility checks 
• Drilling and installation of monitoring wells 
• Collection of initial baseline readings 

Starting this process early provides more time to put the correct monitoring programme in place before winter conditions arrive. 

Waiting until winter to make an appointment could result in an incomplete dataset, which may affect drainage design, planning submissions or regulatory approval. 

Supporting Drainage and SuDS Design 

Groundwater monitoring and infiltration testing are often considered together when assessing drainage options for a development. 

BRE 365 testing assesses how quickly water can infiltrate into the ground. Groundwater monitoring helps establish whether groundwater levels could constrain the location or suitability of an infiltration system. 

A site may have suitable infiltration rates, but a high seasonal groundwater level could still affect the design or position of a proposed soakaway. Considering both sets of information gives the drainage designer a more complete understanding of the site. 

The 2025 National SuDS Standards 

The National standards for sustainable drainage systems, updated in July 2025, place greater emphasis on managing surface water within a development. 

The standards apply to England and establish a hierarchy for the final destination of surface water runoff. Where a lower-priority option is proposed, appropriate evidence must demonstrate that higher-priority options have been used to the maximum extent practicable. 

They also state that the base of an infiltration drainage feature should not be within one metre of the maximum likely groundwater level on the site. 

Reliable groundwater information can therefore help demonstrate whether infiltration is suitable and provide evidence to support the proposed drainage approach. 

Groundwater Monitoring for Highways and Infrastructure 

Understanding groundwater conditions is also important for sustainable and compliant infrastructure design. 

For highways and relevant road infrastructure projects, National Highways LA 113 – Road Drainage and the Water Environment provides the framework for assessing the potential effects of road projects on the water environment. 

Groundwater monitoring can provide baseline information to assess environmental risks, inform drainage design and demonstrate that proposed works will not adversely affect the water environment. 

How is Groundwater Monitoring Undertaken? 

Groundwater monitoring points are generally installed within boreholes at selected locations across the site. The number, position and depth of the monitoring wells will depend on the site conditions and purpose of the investigation. 

Groundwater levels can then be measured during scheduled monitoring visits using calibrated equipment. Where conditions are highly variable or more frequent measurements are required, telemetry and data-logging systems may also be used to record changes over time. 

The results are reviewed by experienced consultants and can be used to support drainage, planning, hydrogeological and development assessments. 

Plan Your Monitoring Programme 

Earth Environmental & Geotechnical provides groundwater monitoring services for developments and infrastructure projects across the UK. 

Our monitoring programmes are tailored to the hydrogeological conditions and requirements of each site. We can provide: 

• Review of site and planning information 
• In-house drilling and installation of monitoring wells 
• Scheduled groundwater monitoring visits 
• Telemetry and continuous data logging where appropriate 
• BRE 365 infiltration testing and trial pitting 
• Interpretation of groundwater data 
• Clear technical reporting to support planning and design 

Monitoring may range from several months to a full seasonal cycle, depending on the site and project requirements. 

If groundwater monitoring may be required for your development, contact our consultants now to allow enough time to prepare for the winter monitoring period.