Freshwater and Estuary – What’s in a Grade?

Our results aren‘t simply pulled out of the sky, they have been prepared using a set of formulas and scores that are applied from the individual sample level all the way to the Basin grade. All of these steps and their application are based on best available science along with the expert knowledge and guidance of our science panel.

Freshwater catchments and Estuary

The freshwater and estuary reporting areas are assessed using indicators, thresholds and a normalising formula.

No Data

grade-n Sometimes there are no data available to assess an indicator. When this is the case a grey N icon is displayed.

Imputed Data

gradeX In some reporting years data are not available for an indicator in one catchment, although they have been available in the previous reporting years. In this case the score is marked with an X and is exchanged with a calculated score.

This calculated score is the previous year’s score for the indicator, which has been adjusted by the average % change at the basin scale, using these steps:

  • Compile all site results for the indicator across all the catchments of the Fitzroy Basin.
  • Remove any sites which don’t have data for both the current year and the previous year.
  • Calculate the Fitzroy Basin average score for the indicator for the current year and for the previous year.
  • Calculate the % change in score between the previous year and the current year.
  • Apply this % change to the indicator score that was the previous year’s score in the catchment with the missing data.
  • Use the calculated value to score the indicator for the catchment.

Marine Zone

The marine reporting area is assessed with a different rating system to the freshwater and estuary reporting areas, find out more here.

How are Grades Awarded?

How the Basin is scored

How the Reporting areas are scored

Indicator categories have a weighted average applied to them. You can see the break-down below.

Category weightings

Each of the indicator categories contibutes a certain percentage towards the overall reporting area score.


Freshwater indicators categories include physical/chemical, nutrtients, toxicants and ecology which contribute 40%, 10%, 25% and 25% respectively to the overall catchment score. Some catchments had no ecology data, in which case physical/chemical, nutrtients, and toxicants contribute 53.3%, 13.3% and 33.3% respectively.


Estuary categories are the same as freshwater, except without toxicants. The Physical/Chemical, Nutrient and Ecology categories contribute 53.3%, 13.3% and 33.3% respectively towards the overall estuary score.


Marine condition for the Fitzroy is available via additional information and does not contribute to the overall score for the basin. The marine condition report is provided by the office of the great barrier reef. It utilizes its own set of category weightings and thresholds and does not affect Fitzroy Partnership’s ecosystem health report card results.

How Monitoring Sites are scored

A flow weighting is applied to catchment indicator grades when they are averaged up to a category grade.
Find out how here.

Formula, Indicators and Thresholds

Assessment Formula

If a sample result for an indicator is better than the benchmark, it scores 100 which is an A. If the sample result is worse than the worst case scenario (WCS) it scores a 0 which is an E. If a sample result is between the benchmark and the WCS, the score is calculated using the formula:formula
This formula standardises the sample result in to a score between 0 and 100, and is based on the formula used in and developed by the South East Queensland Ecosystem Health Monitoring Program.

Indicators and Thresholds

The following table shows all the indicators for the freshwater and estuary reporting areas and the benchmarks and worst case scenarios used in calculating the grades. Use the drop-down menu to change the reporting area.[indicator_threshold_table] (1) All metals are dissolved except Selenium, which is Total (due to no guidelines for dissolved).
(2) WQG = Water Quality Guideline or other benchmark.
(3) WCS = Worst Case Scenario.
Click here to download table as an Excel workbook