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Scientists monitor water quality after recent flood

Hydrographers from Department of Natural Resources and Water monitor water quality in the Fitzroy River during the 2008 floods.

Scientists from several state and federal agencies worked hard during the recent floods in the Fitzroy region, monitoring for sediments, nutrients, and pesticides in the rivers, estuaries, and flood plumes reaching the Great Barrier Reef (GBR) lagoon.

Bob Noble, Principal Scientist with the Department of Natural Resources and Water in the Central West Region,said the recent flood was the first time in 18 years that a major flood event had occurred in the Fitzroy catchment.

“It was a great opportunity for us to don our water proof gear and get out onto the river and marine flood plumes to measure the loads of pollutants entering local waterways,” Mr Noble said.

“Monitoring water quality during floods helps scientists to identify sources of pollutants and develop and refine catchment models which are mathematical ways of estimating water flows and pollutant concentrations arising from different land uses. Results of the monitoring also allow progress towards targets for improved water quality to be assessed.

“Floods are a natural part of the long-term weather pattern in all reef catchments. In natural systems undisturbed by urbanisation, agriculture and industry, flood events do release substances such as sediment onto inshore ecosystems.

“However, with the increase in land used for agriculture, pollutants such as nitrogen and phosphorus (from fertilisers), chemicals (from pesticides) and increased sediment (from land clearing and over-grazing) have found their way onto our Great Barrier Reef.”

The Reef Water Quality Protection Plan (Reef Plan) includes actions to address pollution from broadscale land use, monitor water quality and improve the quality of the water reaching the Reef within the next decade.

These monitoring activities are supported by ambient monitoring programs, community monitoring, and the Great Barrier Reef Marine Park Authority’s Marine Monitoring Programme.

Mr Noblesaid the monitoring process itself includes sampling of water from across the rise and fall of floods at sites in the Fitzroy sub-basins near gauging stations where flow measurements are made.

“Monitoring also occurs downstream in the estuary at Rockhampton, in the plume at inshore areas in Keppel Bay and further offshore in the GBR lagoon,” he said.

“Because the Fitzroy is a very large drainage basin, floods may take many days to pass a river site. Therefore the monitoring program relies on many dedicated people to achieve effective daily sampling of the floods in the catchment and resultant freshwater plume in the adjacent marine areas.

“Strict procedures must be followed in the sampling and dispatch of water samples to laboratories for the results of pollutant concentrations to be reliable and useful.”

Mr Noble said if flood data can be obtained from across the basin, in the estuary and offshore, then the amount of pollutants being generated in the catchment and carried to the marine environment may be calculated.

“More importantly the sources of pollutants can be identified and improved land, water and vegetation management practices put in place to reduce these loads,” he said.

“In the Fitzroy and in other GBR catchments improved management practices on the land are already underway to lower concentrations of pollutants entering riverine and reef environments.

“Together with previous data from the Fitzroy program of the Coastal Cooperative Research Centre, the knowledge gained from current monitoring data will help paint an overall picture of the health of the Fitzroy Basin and estuary and the adjacent GBR reefs.

“The current monitoring delivers action oncalls for co-ordinated water quality monitoring programs in high-risk GBR catchments to track long-term trends in water quality.

“Findings from the monitoring program support the need for the current efforts by land managers in these catchments to improve the quality of water reaching the rivers and the GBR lagoon.”

This activity delivers on Reef Plan Action I5.

Last reviewed 25 June 2008

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