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Index of Wetland Condition (IWC)

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Developer

Victorian Department of Environment, Land, Water and Planning

Latest documentation

2018

Designed for use in

Victoria, Australia

Ongoing

Yes

Assessment purpose

Condition, Management effectiveness, Prioritisation, Processes and components, Values

Assessment criteria

Physical and chemical, Management and planning, Flora

Method type

Field, desktop, laboratory assessment/analysis

Timescale

Rapid term – The field assessment can take anywhere from 45 minutes to half a day depending on the size of the wetland.

Scale

Site/habitat

Wetland system

Lacustrine, Palustrine

Description and method logic

Method purpose

The IWC is used principally to assess wetland condition. The technique also advises management decisions and targets while assessing threats to a wetland. It has six weighted sub-indices based on the characteristics that define wetlands: wetland catchment; physical form; hydrology; soils; water properties; and biota.

Summary

The Index of Wetland Condition (IWC) is a standard method developed in Victoria for rapid assessment of wetland condition. It is based on the state of the biological, physical and chemical components of the wetland ecosystem and their interactions. The method aims to differentiate natural from human induced changes in wetland condition and assist in management decisions. It has six weighted sub-indices based on the characteristics that define wetlands: wetland catchment; physical form; hydrology; soils; water properties; and biota. It is primarily a site/habitat based assessment (individual wetland scale), some measures require wetland catchment scale assessment.

The technique is suitable for use at all naturally occurring, non-flowing wetlands without a marine hydrological influence in Victoria, at any time of the year. It is designed to assess wetland condition in a single visit.

IWC can be used as a tool for surveillance of wetland extent and condition over a 10-20 year timeframe.

Method logic

The IWC takes the form of a hierarchical index. It has six weighted sub-indices based on the characteristics that define wetlands: wetland catchment; physical form; hydrology; soils; water properties; and biota. Possible measures for each sub-index have been selected by identifying commonly accepted and well recognised threats and impacts in Victoria that affect wetland condition and relating them to key ecological components of wetlands. The measures were then assessed against suitability for rapid assessment. A methods manual provides details of how to collect the recommended measures.

The methodology makes use of the IWC wetland mapping tool; a publicly available mapping tool on the DSE website. This is necessary for assessing changes in actual salinity concentration, while also providing evidence for changes in vegetation and wetland fauna from pre-European times.

Each sub-index is scored out of 20. The total index score is then calculated by summing each sub-index score multiplied by its respective weight. The wetland is then assigned a linguistic condition category based on its total numerical score. Refer to the IWC Assessment Procedure for more information.

Criteria groupings of the method

Criteria or sub-indices are based on the characteristics that define wetlands: wetland catchment, physical form, hydrology, soils, water properties and biota.

Data required

Data on pre European salinity, land use adjacent to the wetland, width of wetland buffer, percentage of wetland perimeter with a buffer, reduction in wetland area, wetland area with changed bathymetry, action that have changed the water regime and their severity, nutrient enrichment, degree of wetland soil disturbance and wetland vegetation quality assessment.

Resources required

Expertise required

An understanding / ability to identify and assess wetland Ecological Vegetation Classes in Victoria is required to assess the vegetation component of the IWC. Refer to the IWC Assessment Procedure for more information on necessary skills.

Materials required

Field assessment, field sheets / mobile app for field data entry, desktop mapping, data management system for data curation and reporting

Method outputs

Outputs

IWC result for a wetland in five categories:
  • Very poor
  • Poor
  • Moderate
  • Good
  • Excellent

The methodology also produces disaggregated, unweighted sub-index scores.

Uses

  • Assessing the condition of wetlands in a catchment region 
  • Is a metric in Victoria’s Wetland Tender method
  • Identifying wetlands where threats are operating
  • Assisting with the assessment of management options by comparing the relative effectiveness of different options on improving condition.

Criteria by category

    Physical and chemical

    • Hydrology
      • Change in water regime and severity of change
    • Physical form
      • Change in wetland area
      • Wetland bathymetry disturbance and severity
    • Soil
      • Soil disturbance and severity of disturbance
    • Water
      • Change in salinity
      • Nutrient enrichment

    Management and planning

    • Wetland catchment
      • Adjacent land use intensity
      • Wetland buffer width and proportion of wetland with buffer

    Flora

    • Vegetation
      • Wetland vegetation quality

Review

Recommended user

The technique requires a general expertise in NRM and expertise in wetland Ecological Vegetation Class identification and assessment – i.e. botanical expertise. Various NRM authorities, consultants, botanists and government departments and agencies are likely to use this methodology.

Strengths

  • Rapid assessment
  • Method is regularly updated and reviewed
  • Simple, straightforward and inexpensive
  • Easy to interpret outputs
  • Management/decision support.

Limitations

  • Limited parameters
  • Knowledge gaps in pre-European conditions.

Case studies

(not documented)

Links


References

  1. Department of Environment and Primary Industries (2013), Index of Wetland Condition 2009/10: Statewide assessment of Victoria’s high value wetlands.. [online], Department of Environment and Primary Industries, Melbourne. Available at: https://iwc.vic.gov.au/docs/IWC_Statewide_assessment_condition_of_wetlands_online.pdf.
  2. Department of Environment and Primary Industries (2013), Index of Wetland Condition: Assessment Procedure. [online], Department of Environment and Primary Industries, Melbourne. Available at: https://iwc.vic.gov.au/docs/IWC%20Assessment%20Procedure%20-%20February%202018.pdf.

Last updated: 16 December 2020

This page should be cited as:

Department of Environment and Science, Queensland (2020) Index of Wetland Condition (IWC), WetlandInfo website, accessed 13 May 2021. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/resources/tools/assessment-search-tool/index-of-wetland-condition-iwc/

Queensland Government
WetlandInfo   —   Department of Environment and Science