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Vulnerability of the water environment

FRS planning officers and personnel should understand the sensitivity of local watercourses and groundwater. For areas that drain to environmentally sensitive locations, containing spillages and polluting firewater run-off should be a high priority during the planning process and at incidents.

The impact that a pollution event has on the environment is influenced by the:

  • Toxicity or polluting potential and quantity of the source material
  • Pathway by which the pollution finds its way into the environment
  • Sensitivity of the receiving environment or receptor

The sensitivity of a body of water will be determined by:

  • Its use and status, for example is it used for drinking water abstraction or home to rare plant species
  • The physical conditions at the time, such as temperature, flow rates and chemical composition

A spillage of the same quantity of a hazardous material into a small trout stream directly upstream of a public drinking water intake is likely to have a greater impact than if the discharge was made into the estuary of a large river. Similarly, the effect of a spillage of an organic pollutant such as milk at the same location in a river is likely to be more serious in summer due to lower flows and higher water temperatures. The table below offers some examples of criteria for sensitivity. Note these criteria are for guidance and are not hard and fast rules as other factors may influence them. Guidance from the appropriate environment agency should therefore always be obtained when determining sensitivity of the local environment.

Likely sensitivity of receiving waters in relation to location

Sensitivity

Location

High

Over a major aquifer

High

Within a designated Groundwater Source Protection Zone

High

Within 250m of any well, spring or borehole used for drinking water abstraction other than within a Groundwater Source Zone

High

Above a shallow water table (< 2m and with free-draining ground)

High

Above a fissured rock, for example chalk, posing risk of rapid flow to groundwater or surface water

High

Less than 5km upstream of an important surface water industrial or agricultural abstraction point

High

Firewater or spillage would affect a commercial fishery or a national or internationally important conservation site

High

Firewater or spillage would affect a site of high amenity value

Medium

Situated over a minor aquifer

Medium

Between 5km and 20km upstream of a surface water drinking water abstraction point

Medium

Between 5km and 20km upstream of an important surface water industrial or agricultural abstraction point

Medium

 Firewater or spillage would impact on a coarse fishery or locally important conservation site

Medium

Firewater or spillage would affect a site of moderate amenity value

Low

Situated over a non-aquifer

Low

Outside any designated Groundwater Source Protection Zones

Low

Situated above deep water tables

Low

Situated on low permeable ground such as clay

Low

More than 20km upstream of a surface water drinking water abstraction point

Low

More than 20km upstream of a surface water industrial or commercial abstraction point

Low

Firewater or spillage would have limited impact on fish populations or wildlife

Low

Firewater or spillage would affect a site of limited amenity value