Guidance

Groundwater source protection zones (SPZs)

Find out where SPZs are, what defines the different zones and why the Environment Agency must protect groundwater from pollution.

Groundwater supplies a third of our drinking water. In some areas of southern England, up to 80% of the water you get from your taps is from groundwater. It also keeps many of our rivers flowing.

The Environment Agency must protect groundwater sources used to supply drinking water from pollution. Sources include wells, boreholes and springs. We’ve defined SPZs – they’re zones which show the level of risk to the source from contamination. This could be from any activity that might cause pollution in the area. For example, storing pollutants like petrol underground, soakaways from septic tanks to the ground. The closer the activity, the greater the risk.

We use our Approach to groundwater protection to:

  • put in pollution prevention measures in areas of high risk
  • monitor the activities of nearby potential polluters

Find groundwater SPZs

The maps show 3 main zones:

  • inner – SPZ1
  • outer – SPZ2
  • total catchment – SPZ3

We sometimes apply a fourth zone of special interest.

See how we’ve defined the zones.

You can view the Environment Agency’s groundwater SPZs on MagicMap.

To find the SPZs, from the table of contents on the left hand side, select in this order:

  • designations
  • land-based designations
  • non-statutory
  • source protection zones merged (England) – tick the box

Enter your postcode and size the map. You can use the transparency slider bar under the ‘designations’ sub heading to adjust visibility of place names within the zones.

You can also download groundwater SPZs or view them as a GIS layer from Defra’s data services portal.

When you need to find a groundwater SPZ

You may need to find out if you’re in a SPZ if:

  • your property is not connected to mains drainage – your septic tank or small sewage discharge treatment plant has a soakaway to the ground – this can be a major cause of pollution
  • you’re applying for an environmental permit or other permission and your business carries out activities that may affect groundwater – for example spreading waste to land
  • your business produces bottled water
  • you’re a developer and your proposals have the potential to pollute or harm groundwater
  • you’re a landowner and your land is within a SPZ
  • you’re a source operator, for example you’re a water company
  • you need to define a new SPZ
  • you have an interest in drinking water quality

How we defined the zones

We have used models to estimate:

  • how long it will take for a pollutant to travel from the water below ground (any point below the water table) to the source (the point where water is taken)
  • the area around the source which needs protecting from potential pollutants

Inner zone – SPZ1

This zone is 50 day travel time of pollutant to source with a 50 metres default minimum radius.

Outer zone – SPZ2

This zone is 400 day travel time of pollutant to source. This has a 250 or 500 metres minimum radius around the source depending on the amount of water taken.

Total catchment – SPZ3

This is the area around a supply source within which all the groundwater ends up at the abstraction point. This is the point from where the water is taken. This could extend some distance from the source point.

Extended zones beneath protective cover

We’ve extended some zones to include areas where there is protective geology cover, such as clay. This is because activities below the surface, such as deep drilling, could create pathways for pollutants to enter the groundwater. The maps show them as zones 1c, 2c and 3c.

Zone of special interest – SPZ4

This zone is where local conditions require additional protection.

Technical guidance

You can use the Manual for the production of groundwater source protection zones to find out:

  • how the Environment Agency produced the zones
  • technical details of the methods used
  • how the Environment Agency keeps the zones up to date
  • case studies of using particular methods in different geological settings
Published 1 August 2019