The hydrodynamic regime at John Brewer Reef, Great Barrier Reef

An array of current meters and tide gauges was deployed around John Brewer Reef between March and September 1987. Moorings were located to allow recording of data from the far field and near field of John Brewer Reef. These measurements were used to provide boundary conditions and test the accuracy of the numerical model of circulation around the reef.

The model boundary was defined by CM1, CM2, CM3, CM4, CM5 and CM13. However, the current meters attached to moorings CM5 (deployed 2/4/87) and CM13 (deployed 1/4/87) were not recovered. Mooring CM4 (deployed 2/4/87) drifted to the Whitsunday Islands. The current meter was badly fouled and the data were unusable.

The locations for moorings CM6, CM7, CM8 and CM12 were chosen on the basis of results from a complementary project, where numerical models of hydrodynamics and dispersion were used to simulate the wind, tidal, long-period current and wave circulation around GBR reefs, for examination of dispersal of larvae of the crown-of-thorns starfish.

The transect CM3, CM8 and CM9 was laid to investigate the interaction between John Brewer Reef and Lodestone Reef. These reefs are only 7km apart and by studying both reefs at the same time it was possible to consider inter-reefal recruitment of crown-of-thorns starfish as well as self-seeding. The current meter attached to mooring CM9 (deployed 3/4/87) was not recovered.

Tide gauges were placed at the corners of the model (moorings CM1, CM2, CM4 and TG1) and in the centre of the model, close to John Brewer Reef (TG2). The mooring CM1 drifted from its original position and only data up to the 27/5/87 are considered reliable. Mooring CM4 drifted to the Whitsunday Islands and the data were not considered reliable. The tide gauge (TG2) was placed near the reef to monitor any tidal differences between the reef and the adjacent deep water.

The study utilized ancillary data from a wind gauge placed in the lagoon of John Brewer Reef by AIMS and wind data from Cairns, Cardwell, Townsville and Mackay supplied by the Bureau of Meteorology.