There is a silver lining to recent Fraser Coast floods – the surge of fresh water entering Hervey Bay is providing valuable data for University of Southern Queensland (USQ) and Griffith University research.
USQ’s Associate Professor in Climatology Dr Joachim Ribbe, USQ PhD student Daniel Briewa and scientist Johann Gustafson from Griffith University recently measured the Bay’s water temperature, salinity, turbidity and underwater light as part of an ongoing research project and found this year’s floods provided important information.
“Our main interest is to understand how the oceanic circulation of water moves from one place to another and Hervey Bay’s estuaries and marine life respond to flood and drought events,” Dr Ribbe said.
“This research is particularly important for the sustainable natural resource management of the region. For example, fish larvae are found in estuaries and being non-mobile, they float in water and ocean circulations determine where they go.
“Some years ago sea scallops were brought to larvae stage on land and released into the ocean. Fisheries were to go out many months later but where the larvae went was a mystery.
“That’s the type of knowledge we needed that motivated us to do this work and we continued from there on. It’s been ongoing since 2004 with funding from a range of sources including the Wide Bay Catchment Management Authority. Several publications have already been produced with international collaborators.”
Dr Ribbe said he was among the several scientists who have studied Australian coastal environments and estuaries of significance, including Hervey Bay, and contributed published books such as Climate Alert, Climate Change Monitoring and Strategy published by Sydney University Press.
“My research includes tracking the freshwater discharges from all Hervey Bay estuaries within the Bay itself,” Dr Ribbe said.
“Australia’s estuaries are many and varied. They’re in different climate zones with different patterns and characteristics – some are very wet, others very dry.
“The Hervey Bay region is of special interest because it’s recognised as one of Australia’s most biodiverse marine environments. Including the Great Sandy Strait, it’s referred to as the Great Sandy Biosphere.
“Hervey Bay is classed as a bay but it has the characteristics of an inverse estuary (on a large scale) due to evaporation being higher than precipitation and river runoff. Because very little fresh water came into the Bay during the 10-year drought before 2009, it became inverse more frequently with a near shore high salinity zone and the ocean appears to be fresher (less salt).
“That has implications on how water is being exchanged throughout the whole system. Classical estuaries flush quickly but with inverted estuaries, it takes much longer for water to reach the ocean. That impacts on the ecology, for example with pollutants. There was a sewerage plant accident here a few weeks ago. Sewerage came into the system and being an inverted estuary, it potentially stays here for a longer period.
Dr Ribbe said that with heavy rain in the past two years and now the recent flooding, a lot of fresh water was flowing into the Bay.
“As that water flushes out of the Bay it will lower salinity,” he said.
“What we did on our recent visit was try to find the front between salty Hervey Bay water and the freshwater. We’re studying how long it sits there and how long it takes the Bay’s system to get back to its normal state.”