Solving the Daly dilemma

The legendary Daly River in the Northern Territory, known for its barramundi and crocodiles, is one of those outposts that seem to belong more in a novel than in a science study.

But the river is at the centre of a research project, which aims to fill in the gaps of knowledge on the relationship between land clearing, recharge (replenishment of groundwater) and spring flows.

Funding

Funded with $144,000 from the Australian Government and in-kind support from the Territory Government, the study involves scientists from Charles Darwin University, CSIRO Land & Water and the Northern Territory Government.

Activities

Project manager Steven Tickell said the study's field sites were located in the Douglas-Daly region, 200 kilometres south east of Darwin. A diverse range of disciplines had been applied to the problem including soil water dynamics, vegetation hydrology, canopy micro-meteorology, applied ecology, hydrochemistry and hydrogeology.

"The Daly River flows all year round, mainly due to springs from the Oolloo Dolostone aquifier," Steven said. "These are crucial to the river's water quality and unique water-dependent ecosystems such as hot springs and gorges, as well as to pig nose turtles, saw-fish, freshwater sharks and freshwater stingrays.

"Our current research work attempts to understand the physical processes related to recharge. This will eventually provide scientific basis for future land and water management and help prevent adverse impacts on ecosystems from spring flows into the Daly River."

Achievements

Some of the key findings show that native woodlands use more water than native and improved pastures. It also revealed that recharge increases significantly following clearing.

Spring flow to the rivers will increase in proportion to the increase in recharge. There will be an immediate increase in spring flow when the additional recharge reaches the aquifer (area that carries the water). However, the actual water recharged and any contaminants it might contain, will not discharge to the river for decades.

At the start of the project, it was presumed that recharge was not concentrated or localised. However, the study suggested that recharge beneath native vegetation was dominated by bypass flow and not slow movement through soil. Steven said the most likely mechanism for this was via cracks and root holes in the soil, which are common in the Oolloo Dolostone aquifer.

More information

• Steven Tickell, Project Manager: (08) 8999 3613
• Water Quality in the Daly Region Summary Report: www.nt.gov.au/nreta/naturalresources/water/regions/dalyregion/waterquality

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