Territory Stories

The Water Quality of the Blackmore Estuary., Darwin Harbour: May and June 2001



The Water Quality of the Blackmore Estuary., Darwin Harbour: May and June 2001


Dixon, I. H.; Padovan, Armando V.


E-Publications; E-Books; PublicationNT; Report No. 19/2003




Blackmore Estuary


The primary aim of this study was to obtain data on the water quality of the upper reaches of Blackmore Estuary in Darwin Harbour at a time when development in the catchment is relatively minor. Future development within the Blackmore Estuary catchment may alter the quality of water flowing into the estuary and in turn the main body of Darwin Harbour. Results from this study can be used as a baseline data set, against which to measure any future changes.; Made available via the Publications (Legal Deposit) Act 2004 (NT).

Table of contents

Summary -- Introduction -- Methods -- Results and discussion -- Conclusions -- References -- Appendix A-B




Salinity; Water clarity; Nutrients; Algae

Publisher name

Northern Territory. Department of Infrastructure, Planning and Environment

Place of publication



Report No. 19/2003

Now known as

Northern Territory. Department of Environment and Natural Resources


iii, 69 pages : some colour illustrations, some colour maps, tables ; 30 cm.

File type


Copyright owner

Check within Publication or with content Publisher.

Parent handle


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Page content

43 Total Phosphorus Total phosphorus (TP) consists of mineral phosphorus, and dissolved and particulate organic phosphorus. Average surface concentrations for each location are shown in Figure 29. Surface averages ranged from 0.015 mg L-1 at locations 10 and 11, to 0.036 mg L-1 at location 9 in May, and from 0.014 mg L-1 at location 10, to 0.036 mg L-1 at location 9 in June. There were variations in TP concentration across the channel width, where surface concentrations of TP generally declined from one side of the channel to the other (Figure 30). The greatest variations were of 0.011 mg L-1 (110%) at location 6 in May and 0.005 mg L-1 (42%) at location 10 in June. Temporal changes between May and June did not show any consistent pattern (Figure 29). Concentrations measured at these times were within 0.007 mg L-1 of each other at all locations. Surface concentrations generally decreased with distance from freshwater inflows in May and June (Figure 29). Location 5, however, had lower concentrations of TP in May than some locations further from freshwater inflows. Generally, the tidal creeks, especially Middle Creek, had higher concentrations than the main estuary channel. In a separate study of the main body of Darwin Harbour, Padovan (1997) measured surface TP to be mostly in the range of 0.010 to 0.015 mg L-1 in May and June 1991. These concentrations are generally lower than those measured in Blackmore Estuary, suggesting that by the time phosphorus reaches the main body of the harbour, concentrations are considerably diluted or consumed by the ecosystem. Overall, TP surface concentrations were low, with the highest concentrations measured in the tidal creeks and gradually decreasing with distance from freshwater inflows.

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