Caboolture Region Water Quality Study - Moreton Bay Regional ...

Northern Creeks
5.7.8 Bullock Creek
Final water quality ratings were variable for sites in Bullock Creek. Water clarity was moderate to poor
at all sites, and deteriorating over recent years at BU-d. Turbidity at the most upstream site (BU-d)
was very high, although the box plots show that this assessment is based on a small sample size
(Figure 4d, Appendix E). Nutrient concentrations were good at the three sites monitored, with the
exception of elevated total nitrogen (probably from decaying organic matter() at BU-a.
5.7.9 Elimbah Creek
Elimbah Creek has a number of potential pollutant sources in its catchment, including extensive pine
plantations, turf farm and a poultry farm. Despite this, water quality remained good throughout the
creek. Dissolved oxygen concentrations and pH were both low at the upstream sites, but this is
probably normal for these creeks.
Other studies at upstream sites have found that Elimbah Creek had high concentrations of dissolved
constituents and high iron concentrations, both of which could be related to the natural lithography of
the area (Cullen, 2000). High aluminium concentrations have also been detected, although no source
has been identified (Cullen, 2000). Most other biological and physical indicators have been
categorised as moderate (including riparian vegetation, fish communities, macro-invertebrate
communities, reach environs and aquatic habitats) (SoR, 2001; Langdon, 2001). Aquatic vegetation
and channel diversity, however, have been rated as very poor (SoR, 2001).
Figure 17. Box plot of pH in Elimbah Creek, showing that further from the mouth of the creek, pH is lower, because flushing with
oceanic water from Pumicestone Passage is poorer.
5.7.10 Ningi Creek
Water quality in Ningi Creek varied from good to good, although all sites had low dissolved oxygen
and the most upstream site had low pH. Poor water quality was caused by elevated concentrations of
nitrogen, due in part to increased inputs of organic nitrogen probably from decaying organic matter.
Despite Ningi Creek being classified poor by the SoR (2001), riparian vegetation was in good
condition in the lower reaches and moderate condition in the upper reaches (Appendix G, ANA, 1998).
However, aquatic vegetation, channel diversity and bed stability have been classified as very poor,
very low and unstable respectively (SoR, 2001)
.
36