Water circulation around Britomart Reef, central Great Barrier Reef (July 1979)

A comprehensive study of the hydrodynamics of Britomart Reef was carried out over a 3 week period in July 1979.

An Aanderaa RCM4 current meter was deployed 1.2 m above the seabed in 30 m of water at each of the deep passes south (Site 1) and north (Site 2) of Britomart Reef. Data were recorded at 10 minute intervals for 3 weeks.

Aanderaa RCM4 current meters were also deployed 1.2 m above the seabed at the western entrance to the reef (Site 3), 100 m inside the lagoon from the northern reef flat (Site 4), in the pass between the central and western lagoons (Site 5) and at the southern entrance to the reef (Site 6). Data were recorded at 10 minute intervals for 10 days. Data from sites 5 and 6 are incomplete.

A continuous recording Marinco Q-15 current meter was suspended from a frame at a depth of 90cm above the bottom on the southern reef flat, 100m from the reef edge (Site 7) for 1 week. Another Marinco Q-15 current meter was suspended 1.5m from the surface from a vessel at the northern entrance (Site 8) for one tidal cycle.

A Microdata weather station was mounted on a 10m tower erected on the reef flat between the western and southern entrances (Site O). Data were recorded every 10 minutes. Additional weather data from the Townsville airport were provided by the Commonwealth Bureau of Meteorology.

Three stilling wells were installed beside towers erected approximately 200m apart from the reef edge to the lagoon, across the southern reef flat in the vicinity of Site 7.

Curtain drogues (2m wide x 2m deep), suspended from a surface float connected to a buoy fitted with a radar reflector were deployed in the western lagoon and tracked by radar at half-hourly intervals.

Microscale currents over the southern reef flat were studied qualitatively by observing the movement of dye released at 5 locations between the southern entrance and Site 7.

The surface temperature field in the area was mapped using infra-red photographs from the Nimbus-N satellite.