August 2025: Chemical, Water Quality and Macroinvertebrate Analysis

Alison Loxton
Sep 30, 2025
2 min read

Hi everyone

I trust you are all keeping safe and well.

Currently we have had little rain (a more traditional spring than the last few years) and freshwater levels are quite low. We need around 100mm of rain, spread over several days.

Attached are the results for August, 2025. In respect of explanatory notes please find the following:

Results are fairly even across the catchment except for the pH at Ruth Terrace inflow at Waterhen Lake. The low pH is most likely the result of concentrated inflow from the street without following up rain to spread the concentrated pollutants out into the lake.
Chemical results are somewhat variable with higher levels in Waterhen Lake for the same reason shown in 1 above. There were a couple of spikes in phosphate readings in Regatta Waters, most probably due to people fertilizing their gardens coming into spring. In the upper reaches of the Coomera River estuary there were higher levels of phosphates, reflecting the flow from housing around Yaun Creek, and also a concentration of pollutants at the weir.
It is worth noting the temperature differences between Regatta Waters and the Coomera River – on average the river water moving in and out of the Broadwater is around 3 degrees warmer than Regatta Waters. Likewise, the salinity is higher in the lower reaches of the Coomera River, decreasing as we venture further upstream.
In a spot of good news we undertook a Macroinvertebrate survey in Guanaba Creek; in what were ideal stream conditions, the riffle scored the highest SIGNAL riffle score ever of 6.72, which is way over the healthy minimal score of 6. This was due to a preponderance of mayflies (higher scoring) and an absence of more tolerant (lower scoring) animals. There were so many mayflies that there was little room for other species in the habitat.
We do few Macroinvertebrate sample these days due to rapidly changing stream bed conditions, and also dangerous high water levels. Perhaps in time we may be able to undertake more sampling.

Just a reminder that we will be meeting for our next planting at Regatta Waters Park on Saturday 11^th October commencing at 8.00am.

It would be great to see your smiling faces and to catch up again with good friends.

Kindest regards to you all.

Steven Gill