Darwin Harbour
Integrated Report Card

Sediment Quality Index

The sediment quality index (SQI) includes metal data (copper, lead and zinc) collected from 286 sites throughout Darwin Harbour. Data used in this assessment was first collected in 2020 by the Northern Territory Government. Data is collected by the Northern Territory Government and reported across nine regions that make up Darwin Harbour.

Sediment quality sampling locations and results

Scoring method

Collected data are compared to pre-European conditions to yield an index value on a scale between less than 1 - greater than 4, with an index value of <1 being very good and an index value of 4+ being very poor.

In order to standardise the reporting scale across all indicators, the average sediment quality index for sites within each reporting region was converted to a 0-100 report card scale using the relationship shown in this graph.

Findings

The sediment quality index indicated good conditions for sediment metals in all assessed regions of Darwin Harbour, with an area-weighted average score across all regions of 73% (B). Certain sampling sites, however, did show signs of degraded sediment quality, primarily in East Arm.

Scores have been assigned to Buffalo and Myrmidon Creeks, however these are of low confidence due to limited sample size in each.