Groundwater source protection zones

Understanding the Groundwater Source Protection Zones maps

 

Go to Groundwater Source Protection Zones Map

 

What are Groundwater Source Protection Zones?

Groundwater provides a third of our drinking water in England and Wales, and it also maintains the flow in many of our rivers. In some areas of Southern England, groundwater supplies up to 80% of the drinking water that you get through your taps. It is crucial that we look after these sources and ensure that your water is completely safe to drink.

We have defined Source Protection Zones (SPZs) for 2000 groundwater sources such as wells, boreholes and springs used for public drinking water supply. These zones show the risk of contamination from any activities that might cause pollution in the area. The closer the activity, the greater the risk. The maps show three main zones (inner, outer and total catchment) and a fourth zone of special interest, which we occasionally apply, to a groundwater source.

We use the zones in conjunction with our Groundwater Protection Policy to set up pollution prevention measures in areas which are at a higher risk, and to monitor the activities of potential polluters nearby.

 

Key to understanding the Groundwater Source Protection Zones Map

How do we define groundwater source protection zones?

The shape and size of a zone depends on the condition of the ground, how the groundwater is removed, and other environmental factors. When we define a zone we find out how the groundwater behaves in that area, what constructions there are to get the water out into the public water supply, and the process for doing this. From this we can develop a model of the groundwater environment on which to define the zones.

We divide groundwater source catchments into three zones. The zones are divided as follows:

Groundwater Source Protection Zones

Inner zone<br>(Zone 1) Inner zone (Zone 1) - Defined as the 50 day travel time from any point below the water table to the source. This zone has a minimum radius of 50 metres;

Inner zone - subsurface activity only<br>(Zone 1c) Inner zone - subsurface activity only (Zone 1c) - ;

Outer zone<br>(Zone 2) Outer zone (Zone 2) - Defined by a 400 day travel time from a point below the water table. The previous methodology gave an option to define SPZ2 as the minimum recharge area required to support 25 per cent of the protected yield. This option is no longer available in defining new SPZs and instead this zone has a minimum radius of 250 or 500 metres around the source, depending on the size of the abstraction;

Outer zone - subsurface activity only<br>(Zone 2c) Outer zone - subsurface activity only (Zone 2c) - ;

Total catchment<br>(Zone 3) Total catchment (Zone 3) - Defined as the area around a source within which all groundwater recharge is presumed to be discharged at the source. In confined aquifers, the source catchment may be displaced some distance from the source. For heavily exploited aquifers, the final Source Catchment Protection Zone can be defined as the whole aquifer recharge area where the ratio of groundwater abstraction to aquifer recharge (average recharge multiplied by outcrop area) is >0.75. There is still the need to define individual source protection areas to assist operators in catchment management;

Total catchment - subsurface activity only<br>(Zone 3c) Total catchment - subsurface activity only (Zone 3c) - ;

Special interest<br>(Zone 4) Special interest (Zone 4) - A fourth zone SPZ4 or ‘Zone of Special Interest’ was previously defined for some sources. SPZ4 usually represented a surface water catchment which drains into the aquifer feeding the groundwater supply (i.e. catchment draining to a disappearing stream). In the future this zone will be incorporated into one of the other zones, SPZ 1, 2 or 3, whichever is appropriate in the particular case, or become a safeguard zone.