Water Testing on the Brook

Although the information given below on this web page is over ten years old, it gives an example of the type of water testing being carried out by authoritative organisations in a similar manner to this day. The comments on weeds are still relevant as they are similar to those being made in recent times. Consider the significant effect any recent rain may have on water quality, especially after long dry periods.

For recent observations, look at the results of our Fish Snapshots (past newsletters and news items) and scientific reports such as the Ecosystem Health Monitoring Program (EHMP) managed by the South East Queensland Healthy Waterways Partnership. The 2009 EHMP Report Card groups Kedron Brook in the Lower Brisbane Catchment. This data broadly represents the information given for the water quality feeding into Moreton Bay. The overall score of "F", gained in the 2009 report, indicates our Lower Brisbane Catchments have streams in poor condition.

The recent infrastructure projects along the lower reaches of the Brook have made significant adverse changes to the health and biodiversity of the riparian habitats. [Editor (Feb.2010)]

Brookside Site & Ferny Grove Site
Water Quality Testing
by ACU students, Australian Catholic University waterwatch unit.

The Australian Catholic University at Mitchelton includes a waterwatch component in their pre-service primary teacher course. Part of this unit involves testing at two sites along Kedron Brook for Benthic Macroinvertebrates and physical and chemical water tests.

Brookside Site Location and Riparian Cover.

The first site was at Brookside shopping centre below the road bridge. This area is not in great shape as regards the riparian zone.

Every weed on the Council weed poster.

Just about every weed on the council weed poster is represented in this location. There is very little cover over the stream and consequently it is invaded by cumbungi reeds and para grasses. Weed species present included Lantana, Singapore Daisy, Castor Oil Plant, Japanese Sunflower, Chinese Elm, Maderia Vine and many others. Despite the poor riparian cover the water quality tests were quite reasonable. 

Water quality tests reasonable.

The dissolved oxygen reading for the Brookside site is a little on the low side at 32% saturation. A result of closer to 70-85% would be more appropriate. The temperature may have had something to do with this as it was higher than at the Ferny Grove site

TABLE OF RESULTS

Ferny Grove Site Location and Riparian Cover.

The site at Ferny Grove was near the tennis courts past the Australian Woolshed. This position had a more natural aspect and many more native plants and better riparian cover over the stream.

No flow made testing challenging.

The Brook at this point was not flowing but pooled in shallow areas of rock which made the testing challenging. As can be seen in the table of results the Dissolved Oxygen level at Ferny Grove was much closer to the ideal at 85%. The adequate riparian cover would make a difference here even though there was no flow. The pH readings were both normal and salinity although higher at Brookside was within the normal range. The nutrient tests of PO4 and NO3 were both higher at Ferny Grove. This may have been due to the pooling and hence concentrating of the water in this location. The normal limit for PO4 is 0.05mg/L and for NO3 it is 0.5mg/L. There had also been rain in the twenty four hours before the testing at Brookside which may have flushed the system there although generally rain washes extra nutrients into the stream from surrounding land.

Macro invertebrates found at both sites.

The macro invertebrates or water bugs probably did not reflect the water quality differences at the two sites due to the dry conditions at Ferny Grove.  At Ferny Grove the students found several sensitive groups including Mayfly nymph, Freshwater shrimp, and damselfly nymph. These taxa indicate good water quality and some were found in a little channel running into the Brook near the testing site.

The Ferny Grove site had less diversity of macros with many freshwater crayfish and beetles, bugs and mosquito larvae present. There is normally a larger range of bugs in this site and I am sure it is a reflection of the lack of flow in the stream.

Overall, the water quality in both locations in the Brook was within acceptable levels. The situation at Brookside would be vastly improved by removal of the weeds and restoration of the riparian vegetation that would have been originally there before settlement.

Contact person: Dr Barbara Odgers
Ph. 07 3855 7342

CI   19/02/2010