Townsville SOE home page

A Volunteer Community Awareness
Program for Louisa Creek

Graphs and Tables

2002 - dissolved oxygen (DO) compared to water temp.

Of the three sites monitored, the Banfield Drive site showed only low oxygen readings while Greg Jabs Court site and Bayswater Road site trended together. As water temperature trended gradually down, dissolved oxygen levels trended up until October, when the heat set in and water levels dropped in the lead-in to the “Wet Season”.

Note the gradual trend from ‘very poor’ dissolved oxygen levels (0-45% saturation) through ‘poor’ dissolved oxygen levels (45-65% saturation) to ‘good’ dissolved oxygen levels (65-100% saturation)(see Table 1). This trend was interrupted by late May rain (56.5mm on 26th May which was not enough to flush the creek but lowered dissolved oxygen levels.

Click to open 2002 - dissolved oxygen (DO) compared to water temp graph: PDF
Click image to open
(.pdf 19Kb)


2003 - dissolved oxygen (DO) compared to water temp.

Five of the seven water quality monitoring sites were selected for representative results. Water temperatures trended together, unlike dissolved oxygen results. The differences between dissolved oxygen monthly readings could be explained by water depth as opposed water temperature. As the year moved into the drier months, the results became less comparable between sites.

February’s high temperature and abundant rainfall (58mm on 24th February and 314mm in total for the month) saw first, a lowering of dissolved oxygen levels and then a substantial increase taking the readings from very poor dissolved oxygen levels to good dissolved oxygen levels. The 1st of March saw 56 mm of rainfall contributing to flushing of Louisa Creek. By May and June the rain had backed right off and the water levels would have been dropping causing dissolved oxygen levels to drop as well. The sudden increase in Camuglia St dissolved oxygen levels in September is an anomaly from one reading so is best ignored.

Click to open 2003 - dissolved oxygen (DO) compared to water temp graph: PDF
Click image to open
(.pdf 22Kb)


2004 - dissolved oxygen (DO) compared to water temp.

Water temperature trends were consistent with seasonal variations.

Mid and late February saw substantial rain; 300mm by mid-month with another 96mm falling by the end of month. This heavy rain caused the dissolved oxygen levels to hit bottom and then slowly rise across four of the five sites in April. Late April got moderate rain (60.5mm from 24th to the end of the month) causing another slump. After May dissolved oxygen levels improved. June through October were relatively dry months with the most monthly rainfall being 6.7mm. The dissolved oxygen level generally stayed within the ‘very poor’ to ‘poor’ ranges over the course of the year.

Click to open 2004 - dissolved oxygen (DO) compared to water temp graph: PDF
Click image to open
(.pdf 22Kb)


2002/2003/2004 electrical conductivity.

For 2002 and 2004 the first third of the year saw salinity levels remain in the 0-800 microseimens per centimetre level (see Table 2) with the second trimester seeing the salinity levels move into the 800-2500 range, lessening water quality. The last trimester of the year saw water quality deteriorate and salinity rise above 2500 microseimens per centimetre. This is likely due to water levels dropping and pools gradually drying up.

electrical conductivity
electrical conductivity
electrical conductivity
Click to open 2002 electrical conductivity graph: PDF
Click image to open
(.pdf 14Kb)
Click to open 2003 electrical conductivity graph: PDF
Click image to open
(.pdf 18Kb)
Click to open 2004 electrical conductivity graph: PDF
Click image to open
(.pdf 15Kb)

2003 had sporadic rain events thoughout the dryer portion of the year (10.5mm in June, 38mm in August and 28mm in October). Perhaps as a result the data for 2003 has more peaks and troughs with the salinity level at the end of the year generally being an improvement on 2002 and 2004.

Monthly Rainfall data
Click to open 2002/2003/2004 monthly rainfall graph: PDF
Click image to open
(.pdf 16Kb)


Table 1: Ranges of water quality and waterway health as determined by dissolved oxygen levels for slow to no flow drains and streams.

DO % Saturation Range
0-45 % very poor
45-65% poor
65-100% good
100%+ poor

Table 2: Ranges of water quality and waterway health as determined by salinity level and suitable uses.

Salinity (EC- µs/cm) Use
0-800 Good drinking water for humans
800-2500 Good for irrigation, drinking water for livestock
2500-10,000 Not for human consumption, not normally for irrigation
›10,000 Not suitable for irrigation or livestock(50,000 is seawater)


Concluding comments:
Although any results can only be preliminary, indications are that dissolved oxygen and electrical conductivity are quickly affected by rain events and subsequent water levels. The data plus anecdotal evidence indicates that the flushes caused by initial rain events see water quality deteriorate, while follow-up rain on top of raised water levels and which cause the creek to flow improves water quality. This would suggest eutrophication is a significant factor in this waterway's health. Observations would indicate that both natural eutrophication and cultural eutrophication are contributing to poor water quality, although to what degree each contributes is open to question.
Townsville City Council Home PageCouncil's Environment Management Services