Erosion and irrigated agriculture in northern Australia

18 September 2015

North Queensland’s Gilbert catchment has long been recognised for its potential for large scale irrigated agriculture. While this sort of development is likely to generate a wide range of benefits, it also has its challenges, especially in an area highly prone to erosion.

Senior research fellow with the Australian Rivers Institute at Griffith University, Dr Andrew Brooks, has been investigating how new irrigation developments can be planned and implemented to minimise the risk of erosion.

“Major erosion not only poses a major environmental risk, but a risk to the viability of any new development in northern Australia,” he said.

“Using the Gilbert catchment as a case study, the results of this project can help developers and landholders better understand the areas at risk of erosion and to minimise its acceleration. There are a range of logistical issues that need to be considered to ensure that landscape degradation doesn’t result from the transformation of the region’s current low density grazing land use, to high intensity irrigated agriculture.”

A presentation titled The promise vs the reality of irrigated agriculture in northern Australia was delivered by Dr Brooks to the Australian Government and discussed the challenges of agriculture within the ancient fragile soils of the Gulf Country. The presentation focused on a major proposal in the Gilbert River catchment to create an integrated farm and processing precinct producing mainly sugar and guar beans for the Asian market.

“This new proposal is utilising an approach called fertigation, where fertiliser is dissolved and distributed within the water of the irrigation system, in a process akin to large scale hydroponics. The approach has been typically used on smaller scale projects where the water and nutrients are delivered via drip irrigation, however, in this proposal it is intended to be delivered via a furrow irrigation system,” Dr Brooks said.

“The use of furrow irrigation on these sorts of soils, in this landscape, raises serious concerns in our minds regarding the potential for initiating significant erosion given the poor structure of many soils in the area of interest. This approach changes the emphasis for site selection to locations suitable for water infrastructure development, while soil quality is a secondary consideration.”

“This case study highlights the development constraints associated with topography and soil structure. The assessment of soil erosion susceptibility must be ranked as one of the highest priorities for consideration in the planning processes for any new agricultural development in northern Australia.”

Dr Brooks also discussed the potential impacts the water extraction needed for the development could have on habitat values of the Einasleigh and Etheridge Rivers, as well as the Gilbert River downstream. For more information about this research, click here.

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