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January 2025: Chemical, Water Quality and Macroinvertebrate Analysis
- Alison Loxton
- Feb 25
- 2 min read
Hi everyone,
Welcome to the report for Water Quality Monitoring for January 2025.
The first thing you will notice is the variation in turbidity across the sampling area.
We have excessive turbidity across a wide range, from Nerang to the weir in the Coomera River.
This was due to the constant and excessive rainfall we have experienced. As an example, we look at the turbidity readings which measure the amount of sediment in the stream or river – Waterhen Lake we expect, however the readings at the Weir and the main Coomera River itself are greater than normal
In addition, when we look at the chemical readings, we find excessive levels of reactive phosphates, primarily in Waterhen Lake but also in the Coomera River itself.
Along the length of the Coomera River, it is difficult to explain the readings ranging from 0.21 mg/l to 0.41 mg/l; ordinarily we expect readings up to 0.12mg/l however this level of phosphates equates to a great deal of fertilizer being utilised across the catchment. It is possible what has happened is that crops or pasture have been fertilized, and the constant rainfall has simple dissolved it and washed it into the river. Whatever the cause it does beg an explanation.
By way of contrast, the ammonia nitrogen levels have been relatively low; this is a positive as ammonia nitrogen is linked primarily to animal and human waste.
It is to be hoped that with less rainfall and given time to stabilize the river levels, that the excessive readings will adjust to more acceptable levels in the weeks ahead.
In better news we did undertake a Macroinvertebrate sample in Guanaba Creek. This resulted in the highest SIGNAL score I can recall in eight years of sampling. The reading of 6.78 is at the higher end of SIGNAL scores where 6 and above denotes a healthy water system. Of some interest is that the reactive phosphates level was 0.21mg/l, showing little impact on the SIGNAL score. Food for thought.
Kind regards
Steven Gill
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