Water Quality Index
The water quality index (WQI) includes nutrient and chlorophyll-a data collected routinely from 93 sites, and physico-chemical data collected via underway monitoring throughout Darwin Harbour for the year 2020. Data is collected by the Northern Territory Government and reported across nine regions that make up Darwin Harbour.
For further information: https://depws.nt.gov.au/water/water-management/darwin-harbour/Darwin-Harbour-water-monitoring.
Scoring method
Collected data are compared to guidelines to yield an index value on a scale between 0-1, with an index value of 0 reflecting no data met guidelines, and an index value of 1 indicating that all values have met their respective guideline.
In order to standardise the reporting scale across all indicators, the average water 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 water quality index identified good to very good water quality conditions in most regions of Darwin Harbour, with an area-weighted average score across all regions of 67% (B). Certain areas, however, did show signs of degraded water quality including a poor grade for Buffalo Creek (D) and a moderate grade for Myrmidon Creek (C+). Buffalo Creek is influenced by treated effluent from the Leanyer-Sanderson waste stabilisation ponds. Myrmidon Creek receives treated effluent from the Palmerston waste stabilisation ponds.
