Freshwater highly disturbed condition (HD)

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Highly disturbed condition of freshwater ecosystems is defined by ANZECC 2000 as “ measurably degraded ecosystems of lower ecological value. Examples of highly disturbed systems would be some shipping ports and sections of harbours serving coastal cities, urban streams receiving road and stormwater runoff, or rural streams receiving runoff from intensive horticulture. This third ecosystem condition recognises that degraded aquatic ecosystems still retain, or after rehabilitation may have, ecological or conservation values, but for practical reasons it may not be feasible to return them to slightly to moderately disturbed condition.”

Highly disturbed freshwater ecosystems

Freshwater wetland locations (e.g. mapped as ‘Riverine’, ‘Lacustrine’ or ‘Palustrine’ Wetland in the Qld EPA Wetland mapping) that have been identified by a technical panel or other information sources as having a high degree of change.

Significant conservation values/remnant natural assets will also be identified in these waterways (so that these can be recognised for protection/improvement).

Depending on availability of information, additional sub categories may be identified for this category:

  • HD a – Highly disturbed waterways identified as having relatively less disturbance than other slightly modified systems (with greater capacity for improvement to MD condition).
  • HD b – Highly disturbed waterways identified as having other significant conservation values/remnant natural assets.
  • HD c – Other highly disturbed waterways.

Management intent for HD freshwater ecosystems

ANZECC, 2000; p3.1-22: “The guidelines recommend that guideline trigger values for slightly to moderately disturbed systems also be applied to highly disturbed systems wherever possible. If that is not possible, local jurisdictions and relevant stakeholders must negotiate alternative values. For this situation the Guidelines provide less conservative values for toxicants.”

ANZECC, 2000; p3.2-19: “The philosophy of the Guidelines for these systems is that at worst, water quality is maintained. Ideally the longer term aim is towards improved water quality”

Water quality guidelines to protect HD freshwater ecosystems

The following HD guidelines are provided in recognition that it may not always be practical to improve a HD system back into a MD condition, particularly in the short term.

  • Toxicants in water: Locally determined, e.g. 10th/90th percentile of reference range (QWQG, 2006; Tables 3.4.3, 3.4.4, ANZECC Table 3.4.2)
  • Toxicants in sediments: 80–90% spp protected with 50% certainty
  • Physico-chemical: Guideline locally derived based on:

a) a less stringent percentile e.g. 10th and/or 90th or b) reference data from more impacted but still acceptable reference sites (QWQG, 2006; Tables 3.4.3, 3.4.4)

  • Biological: Guideline locally derived based on:

a) a less stringent percentile e.g. 10th and/or 90th or

b) reference data from more impacted but still acceptable reference sites (QWQG, 2006; Tables 3.4.3, 3.4.4)

References

Running River © NQ Dry Tropics 2014
Running River © NQ Dry Tropics 2014

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