Hotspots

A sediment, nutrient or pathogen hotspot is an area where there is a high concentration and/or loading of a pollutant and a high risk of the pollutant leaving the site and entering a water body (e.g. river, lake, estuary, groundwater or the marine environment) to cause water pollution. Transport of the pollutant may occur through surface runoff, groundwater infiltration and/or wind erosion.

The impact that a hotspot has on the aquatic environment is influenced by a range of factors, including:

  • distance to a water body (in general, the amount or load of pollutant entering a water body decreases with an increasing distance from the pollutant source)
  • condition of riparian vegetation (riparian vegetation generally acts to capture a proportion of the pollutant load transported in surface runoff)
  • presence and effectiveness of existing mitigation measures (e.g. well maintained sediment basins will capture a portion of the sediment before runoff reaches a water body).

Other factors that affect what impact a pollutant will have on a water body include the vulnerability of a water body and the environmental values of a water body (see below).

Vulnerability of a water body

This includes factors such as the:

  • sensitivity of plant and animal species present in a water body to a particular pollutant(s)
  • flushing capacity of a water body
  • ability of the water body to assimilate the pollutant(s)
  • cumulative impacts with other pollutants.

Environmental values of a water body

For each catchment in NSW, the state government has endorsed the community's environmental values for water, known as Water Quality Objectives and Marine Water Quality Objectives.

The Water Quality Objectives are the environmental values and long-term goals for consideration when assessing and managing the likely impact of activities on waterways. They help industry, the community, planning authorities and regulators when making decisions affecting the future of a waterway and when selecting the most appropriate management options.

Pollutants can negatively impact on the environmental values or uses of a water body that the community believes are important, such as supporting aquatic ecosystems, providing agricultural water and recreation.

Particular water quality characteristics are required to support these values. The presence of faecal coliforms, for example, is used as an indicator for recreational and drinking water quality because this directly puts those uses at risk, but it is not an indicator for the protection of aquatic ecosystems.

Refer to the Australian and New Zealand guidelines for fresh and marine water quality (http://www.environment.gov.au/water/quality/nwqms/) for further guidance for conserving ambient water quality in our rivers, lakes, estuaries and marine waters.

Page last updated: 26 February 2011