TRaCK: Tropical Rivers and Coastal Knowledge

Science and knowledge that governments, communities, industries for sustainable use of Australia's tropical rivers and estuaries

Water resource development must be based on good science

Water resource development must be based on good science

Professor Michael Douglas is based at Charles Darwin University, and is the Director of the Tropical Rivers and Coastal Knowledge Research Hub. Below he outlines why history suggests that the challenges to developing large-scale agricultural schemes in northern Australia should not be under-estimated, as they can’t be easily overcome.

In 1993, the consultants Hassals concluded that in its first 40 years, the Ord Irrigation Scheme had incurred losses that would now equate to $678 million dollars. This was mostly public funds and in 2009 governments invested a further $415 million in the expansion of Ord Scheme. But despite the large investments and long period of operation, this scheme is still a long way from being the “food bowl” that was envisaged.

This time around, the debate about how to develop our water resources in the north can be based on much better science, and it is prudent to ensure that large-scale agricultural developments are sustainable.

The most recent inquiry into the north was the Northern Australia Land and Water Taskforce, which delivered its final report in 2009.

It concluded:

  • That the north is water limited for much of the year.
  • There is limited capacity to store and use surface water due to climate and topography.
  • There are limited areas of good soils particularly where there is water availability.
  • Groundwater is the best option for new consumptive use, with about 600 Gigalitres potentially available.
  • This could support a 2-4 fold increase in irrigated agriculture which equates to roughly a further 20-40,000 ha.

The report was much more conservative in its findings than past assessments of the region’s agricultural potential, largely because it acknowledged some of the basic challenges to agriculture in the north, particularly water availability.

For decades, there have been overly optimistic assessments about the potential for development in the north, and yet the fundamental challenges to tropical agriculture remain.  

People have to be aware that these decisions are about trade-offs. If you take water out to benefit one sector, you are likely doing so at the expense of another. And so we should make the best use of the information we have to ensure that we are making well-informed decisions, particularly when we are talking about dams which are very expensive infrastructure, with potentially irreversible consequences for the environment and downstream communities.

New research from TRaCK (the Tropical Rivers and Coastal Knowledge Research Hub) has highlighted the challenges to achieving sustainable development by reinforcing the importance of free-flowing rivers in supporting biodiversity, fisheries and Indigenous use.

A survey of over 1,000 people across Australia found that most people value a balance between agricultural and other ecosystem services. When asked to choose the most important management issue, 40% of the respondents ranked ‘Preserving Australia’s tropical rivers for biodiversity and natural habitat’ as their first choice and a further 20% chose ‘Preserving rivers for the people who live there and visitors’. ‘Producing food for Australia’ was ranked first by 30% of people, whereas ‘Developing northern Australia’ and  ‘Providing food for the world’ were ranked first by only 6% and 4% of people. People value the use of tropical rivers for agricultural production but not at the expense of Aboriginal, environmental and recreational values. They prefer moderate rather than large-scale irrigated agricultural development in the Daly, Mitchell and Fitzroy catchments.

There is a perception that wet season flows in the north are ‘wasted’, but TRaCK research showed a direct correlation between river flows and the commercial and recreational catches of coastal fish such as barramundi and king threadfin. Others have shown the same pattern for prawns.

Large floods that spill over the banks have many benefits for these rivers.  Many fish move onto the floodplains to feed then move back out to the river as the floodplains dry. This means that much of the meat on barramundi in the upper reaches of river systems may have been “grown” on the floodplains, potentially many months before and hundreds of kilometres downstream. For other fish the floodplains are crucial for breeding with all of the growth of their reproductive organs occurring while they feed on the floodplains.

Large wet season floods are also necessary to connect the floodplains to the river and allow movement throughout the river system, while maintain dry season flows may be essential for the life cycles of important species. For example, barramundi and freshwater prawns need to be able to move upstream from the coast as they grow faster in fresh water. In fact, about one third of the fish found in rivers like the Daly River need to move between salt water and fresh water to complete their life cycle.

Fish like black bream rely on the fast flowing river parts of the river in the dry season for breeding and these areas are critical habitat for the juvenile black bream. Reduced dry season flows will reduce black bream and barramundi populations.

The harvest of these river resources makes a significant contribution to Aboriginal people’s diets and household budgets.  Many of the species that are important for customary harvest, like long-necked turtles, black bream, barramundi and mullet are at high risk from reduced river flows.

Aboriginal people living in these catchments have a lot to lose from developments that reduce river flows, but relatively little to gain. There is an asymmetric divide between Indigenous and Non-Indigenous economic systems in these catchments. Given the lack of employment and business opportunities, workplace skills, and the other infrastructure prerequisites for development, local Indigenous people are likely to see little financial benefit from the expansion of irrigated agriculture.
This new research from TRaCK reveals a much broader understanding of the potential values associated with tropical rivers and this highlights a much greater range of the environmental, social and cultural risks of dam construction or flood harvesting.

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For interviews please contact:
TRaCK Knowledge & Adoption Coordinator Amy Kimber on (08) 8946 7619; 0428 853 425 or