What shape are our rivers really in?

Posted 8 May 2009

Dr Wendy Craik

The answer to the question 'What shape are our rivers really in?' is, unfortunately, easy but not very gratifying.

In June 2008 I received the first Murray-Darling Basin-wide river health check report on the ecological health of 23 river valleys, the culmination of a three-year systematic assessment of the ecological health of the river ecosystems.

The report was not a happy one - it found evidence of long-term environmental and ecological degradation in nearly all of the basin's river valleys.

The Sustainable Rivers Audit is an ongoing program costing $2.5 million a year and reporting every three years. This is an ongoing, comprehensive study, which spans four states and 96,000 kilometres of rivers and streams.

The 2008 report was the first in a triennial series of reports analysing the trends in the rivers of the Basin - an ongoing collaboration between the Murray-Darling Basin Commission (MDBC) and governments of the six basin jurisdictions.

The assessment used data gathered by the state agencies in 2004-07 on hydrology, fish and macroinvertebrates as indicators of river health. Data experts, ecologists and fish and macroinvertebrate specialists from the MDBC and state agencies selected the sites, determined protocols and the data to be collected. They collated the data, generated the databases and then handed them over to the Independent Sustainable Rivers Audit Group (ISRAG) - a panel of four independent ecologists who interpreted it and wrote the report. The panel comprised Dr Peter Davies (Chairman), Dr John Harris, Dr Terry Hillman, Associate Professor Keith Walker.

The report found that valleys in the northern Basin were generally in better health than in the southern part of the basin. Of the 23 river valley ecosystems studied, only the Paroo Valley was in good health. The Border River and Condamine Valleys were judged to be in moderate health. Seven other valleys were in poor health and 13 in very poor health.

The report ranked the valleys' river health from best to worst. The table (page 18) shows condition and ecosystem health assessments for all valleys.

When all valleys were ranked by ecosystem health rating, the Murray Lower and Darling valleys were toward the middle. This indicates that impacts are not simplistically cumulative from headwaters to the mouth of the Murray.

While the numbers and biomass of alien and native fish varied widely among valleys, alien fish rivalled or outnumbered native fish in nine of the 23 valleys. Twenty-eight of the 38 fish species found were native, but the 10 alien species formed 43 per cent of abundance and weighed 68 per cent of biomass.

Three alien species (common carp, gambusia and goldfish) were found in all rivers. Redfin perch and trout species were also widespread. Common carp made up 58 per cent of the total fish biomass. Most valleys showed reduced macroinvertebrate diversity compared with benchmark conditions. This was especially striking for the Avoca, Lower Murray and Warrego Valleys.

A high proportion of sites identified as being in poor condition for hydrology were on the main channels of the basin's principal rivers, particularly in the lowland zones.

While the drought will have influenced fish and macroinvertebrate results, complex interactions and timelags make it difficult to predict the nature of these effects.

However, the hydrological assessments accounted for the effects of climatic conditions, including wet and dry periods. The results therefore reflected long-term water resource development impacts on the flow regime, rather than the recent prevailing drought.

Thus, even for sites rated as near benchmark condition for hydrology, the ecosystem may still have been under stress from drought.

The report was a landmark in one of the MDBC's most important programs. It is one of the largest ecological monitoring programs in the world, easily in the top four in terms of area covered, river and stream length, number of samples collected and jurisdictions covered.

While we have been aware of the degradation of our river system for some time, this sort of comprehensive study gives us the detailed data we need to plan for the future. This is the first basin-wide assessment of ecological health and gives a comparison of how the rivers look now against how they would have looked if people had not made significant changes to them and their catchments.

It is an important reconstructed benchmark for comparison, but greater significance will come as the assessment is repeated in future years, giving us the ability to track change over time.

The next report, due in 2011, will be more comprehensive, including assessments of riverine vegetation and physical form. We can only hope that it reports some improvement to the obviously degraded rivers and streams throughout the vast area of the basin.

Condition and ecosystem health assessments for valleys in the Murray-Darling basin, 2004-07

RankValleyEcosystem healthCondition
HydrologyFishMacro-invertebrates
1ParooGoodGoodModerateModerate
2Border RiversModerateModerateModerateModerate
2CondamineModerateModerateModeratePoor
3NamoiPoorGoodPoorPoor
3OvensPoorGoodPoorPoor
3WarregoPoorGoodPoorPoor
4GwydirPoorModerate to goodPoorPoor
5DarlingPoorPoorPoorPoor
5Murray, LowerPoorPoorPoorPoor
5Murray, CentralPoorModeratePoorPoor
6Murray, UpperVery poorModerate to goodExtremely poorModerate
6WimmeraVery poorPoorPoorPoor
7AvocaVery poorModerate to goodPoorVery poor
7BrokenVery poorModerate to goodVery poorPoor
7MacquarieVery poorModerate to goodVery goodPoor
8CampaspeVery poorModerateExtremely poorPoor
8CastlereaghVery poorGoodExtremely poorPoor
8KiewaVery poorGoodVery poorPoor
8LachlanVery poorModerate to goodExtremely poorPoor
8LoddonVery poorModerateExtremely poorPoor
8Mitta MittaVery poorGoodExtremely poorPoor
9GoulburnVery poorPoorExtremely poorPoor
9MurrumbidgeeVery poorPoor to moderateExtremely poorPoor

Dr Wendy Craik AM FTSE was Chief Executive of the Murray-Darling Basin Commission (MDBC). She was previously President of the National Competition Council, and Chair of the Australian Fisheries Management Authority and of the National Rural Advisory Council. Other former positions include Chief Executive Officer of Earth Sanctuaries Ltd, a publicly listed company specialising in conservation and eco-tourism, Executive Director of the National Farmers' Federation, and Executive Officer of the Great Barrier Reef Marine Park Authority. She has also worked as a consultant for AcilTasman Consulting. Dr Craik is a member of the Board of the Foundation for Rural and Regional Renewal.

Source:

Australian Academy of Technological Sciences and Engineering ATSE Focus web site.

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