Oxley Creek Turbidity Watch 2001

National Science Week and National Water Week
4 -13th May, 2001 and 14 - 20th October, 2001

What is Turbidity Watch 2001?

The Problem!

Oxley Creek is a polluted waterway on the Southside of Brisbane. Turbidity levels are extremely high. The cause of these high levels ranges from sand extraction operations in the catchment, the erosion of creek banks and the release of sediment into storm water drains.

Increased levels of particles in waterways leads to reduced biodiversity by reducing the amount of light penetrating the water, smothering aquatic plants and clogging filter feeding animals, and absorbing heat from the sun and so increasing water temperature.

The Task!

To highlight the problem of turbidity in the creek, Oxley Creek Waterwatch is conducting Turbidity Watch 2001.

Schools, volunteers, community groups and sand extractors are invited to participate by monitoring the turbidity levels of their local waterway or drain. Data collected over the two weeks (in May and October) will be collated by the Turbidity Watch Coordinator to give a Catchment Snapshot. The Catchment Snapshot will be placed on the Oxley Creek website. Click here to see Turbidity Watch 2001 results

Measuring Turbidity is easy!

The Turbidity Watch Coordinator can show you how. A special plastic measuring tube is used to view a water sample. It is that easy!! Data sheets will be provided. If you would like the Coordinator to give an introductory talk to your group, just ask!

See where Sand for Building Materials Comes From!

It is an eye opener visiting the CSR Sand Quarry on Oxley Creek. Small groups are welcome for tours. Contact Mick Horan on 3272 0299.For more information and to book for Turbidity Watch, contact the Oxley Creek Catchment Association on 3278 2899 or write to us at PO Box 217 Sherwood 4075, email occa@flatrate.net.au

How do I do Turbidity Watch?

About turbidity

Turbidity is a measure of water clarity, that is, how much the particles suspended in the water decrease the passage of light through the water. Particles include soil particles (clay, silt and sand), algae, plankton, microorganisms, and other substances. To the naked eye, turbidity appears as cloudy or muddy water. It differs from colour; water can have high colour and low turbidity, for example, tannin rich waters that flow through peaty areas are naturally brown but can have very low turbidity. Although turbidity measures the effect the particles in the water have on water clarity, it does not actually measure the concentration of these particles.

Equipment

Turbidity tube (measures Nephelometric Turbidity Units or NTUs)

Directions

1. Join the two parts of the turbidity tube together.
2. Collect a sample of stream water being careful not to disturb the sediments on the bottom. Lower your collection container 20cm below the surface of the water.
3. Shake your sample before examination.
4. Stand the turbidity tube on its base with a white background so that the three wavy lines on the bottom can be clearly seen when looking down the tube.
5. Pour the water sample into the tube while looking vertically down the tube.
6. Stop pouring at the point where the wavy lines on the bottom are just visible.
7. Record the NTUs by reading the scale on the side of the tube.
8. Pour a small amount of the sample out of the tube and repeat steps 5 to 7, to verify the result.
9. Average the results obtained for the sample.
10. If delayed testing is unavoidable, samples should be stored in the dark for no longer than 24 hours.

Interpreting your results

Turbidity is caused by the presence of suspended material in the water. This suspended material cancome from silt from streambank or bed erosion, plant and animal material, and industrial discharge. Turbidity usually increases after rainfall. However, smaller increases should be observed where the catchment is well vegetated compared to catchments with little vegetation cover.

Stormwater drains can contribute large quantities of silt and leaves to the waterway. High turbidity levels prevent light from entering the water. This, in turn reduces the amount of light available for plant growth with a resulting drop in the oxygen level of the water. High turbidity causes an increase in the temperature of the water because the suspended material absorbs heat from the sun. Increased turbidity can be associated with increases in some pollutants because the metals, pesticides, and nutrients are attached to the particles in the water.

High turbidity levels will lead to a decrease in the biodiversity of a waterway.

Under normal flow conditions, turbidity should be less than 20 – 50 NTU. At high flows, the turbidity values can be much higher. Click here to see the Turbidity Watch 2001 results

Participant List Turbidity Watch 2001

Participant list at 30^th March, 2001