Quarterly results January to March 2024
In response to the flooding events and fish deaths in March 2023, the NSW Environment Protection Authority (EPA), in partnership with the Department of Climate Change, Energy, the Environment and Water (DCCEEW) are monitoring the health of the Darling-Baaka River. The aim is to increase our knowledge of the river system and to deliver a river health monitoring program to assess the aquatic ecosystems and their recovery.
This report provides an initial assessment of the river's health between January and March 2024, based on key water quality indicators. Some data are still undergoing analysis.
Water samples were taken monthly from 20 sites along the river (see table below). Measurements included temperature, dissolved oxygen (DO), nutrients, pH, chlorophyll-a, algae and pesticides. Four smart buoys with automatic monitoring stations recorded water quality every 30 minutes.
Nutrients - Total Nitrogen (TN) and Total Phosphorus (TP)
Samples showed consistently high levels of TN and TP. Many samples exceeded guidelines for lowland river ecosystems in NSW (ANZG 2018). On average TN and TP exceeded these guidelines by up to 1.8 and 2 times respectively. High nutrients levels can lead to algal blooms and may be harmful to animals and humans.
Pesticides and Metals
Pesticides were tested from water and sediments. Seven sites were sampled monthly with 2 additional sites (Lake Wetherell and Wilcannia) sampled in February, and 32 sediment sites sampled in the Menindee weir pool in March. No chemicals were found to exceed the guideline values for toxicity (ANZECC & ARMCANZ 2000). The only pesticide detected was atrazine, at levels well below the guideline values of 13µg/L. Eighteen water samples, and five sediment samples were tested for 11 metals during March 2024. All samples contained metals below the default guideline values.
Algae
Algal biomass (indicated from chlorophyll-a) was very high, ranging between 20-130 μg/L. The algal biomass saw increases in potentially toxic cyanobacteria. Further analysis of algal dynamics is underway and will be reported in subsequent reports.
Dissolved Oxygen (DO)
All DO records fell within the guidelines, except site B3 which had values below 2mg/L in January and 4mg/L in February. Low DO concentrations can cause harm to aquatic life.
Overall assessment
The areas of concern for the current samples were elevated nutrient and algal levels. Further analysis of algal species is underway. Analysis of the most appropriate water quality guidelines to use for the Darling-Baaka system is occurring and will be addressed in future reports
Contact enquiries.waterscience@environment.nsw.gov.au for more information
Future sampling
DCCEEW has expanded sampling of river health to include 34 sites between Wilcannia and Wentworth. Sampling for these sites will start in June, and will include biological indicators of river health such as fish and macroinvertebrates.
Water quality summary
Date 1: 31 Jan–2 Feb Date 2: 19–22 Feb Date 3: 25–28 Mar
| Sampling site |
Dissolved oxygen |
Nutrients | Pesticides | Metals | |||||||||||
| Date 1 |
Date 2 |
Date 3 |
Date 1 |
Date 2 |
Date 3 |
Date 1 |
Date 2 |
Date 3 |
Date 1 |
Date 2 |
Date 3 |
||||
| TN | TP | TN | TP | TN | TP | ||||||||||
| E1 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | ✓* | ✓ | ||
| E2 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | ✓* | ✓# | ||
| E3 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | ✓* | ✓# | ||
| E4 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | ✓ | ✓* | ✓# | ||
| E5 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | ✓* | ✓# | ||
| E6 | ✓ | ✗ | ✓ | ✗ | ✓ | ||||||||||
| E6.5 | ✓ | ✓ | ✓ | ✗ | ✓ | ✗ | ✓ | ✗ | ✓ | ✓ | |||||
| E7 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✓ | ✗ | ✓ | ✓ | |||||
| E8 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | |||||
| E9 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | |||||
| E10 | ✗ | ✗ | |||||||||||||
| E11 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | |||||
| E12 | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | ||||||
| E13 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | |||||
| E14 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | |||||
| E15 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | |||||
| B1 | ✓ | ✓ | ✓ | ✗ | ✓ | ✗ | ✓ | ✗ | ✗ | ✓ | |||||
| B2 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | ✓ | |||
| B3 | ✗ | ? | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ | ✓* | ✓# | ||
| B4 | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ | ✓ | ✗ | ✓ | ✓ | |||||
✓ Meets guidelines ✗ Outside of guidelines
? Potentially stressful for aquatic life
* Sediment samples # Water and sediment samples
Guidelines used are for lowland river ecosystems in NSW (ANZG 2018)
