Salinity research is challenging old theories

The ongoing eight Key Sites salinity research project is delivering results that contradict conventional thinking when it comes to effective salinity management in NSW.

Orange-based NSW DPI salinity specialist, David Mitchell, said the project for salinity, hydrology and model validation aimed to quantify the components of water and salt balances, and severity of salinity.

"Eight sites around the State are being used to better understand where the salt and water is moving and what effect this has on telltale symptoms of salinity such as saline scalds, salt load movements, reduced groundcover and degraded native pastures," Mr Mitchell said.

Mr Mitchell said sites at Gumble, Livingstone Creek, Boorowa and Baldry had revealed interesting trends and information that would better guide land management decisions.

Gumble

Data collected from the Gumble site has revealed that scald is fed by a confined saline aquifer that is recharged by the hills under native vegetation.

In this case, clearing of land did not lead to saline scald, rather it is the subsequent management of the land that led to excessive erosion and subsequent deposition that caused the scald.

Boorowa

Research into the effect of land use on water and salt movement on the Southwest Slopes has shown that farming systems have direct influence on the control and mitigation of dryland salinity.

Recent analysis of long-term data on the Boorowa site by a number of researchers has shown that conversion from annual cropping to perennial pastures with tree belts has had a significant effect on the hydrology of the site.

In particular the role of perennial pastures has reduced recharge to below measurable levels, runoff has been significantly reduced and the amount of salt being exported by the sub-catchment has been halved.

Livingstone Creek

The data collected from Livingstone Creek (story preceding page) has provided an increased understanding of the movement of salt loads in alluvial soil, and in particular the site has revealed how the condition of a catchment determines the amount and types of salt exported.

The alluvial flats which predominately are under annual cropping are flushed by rainfall and the soil is maintained relatively fresh.

This finding suggests that removal of the leaky annual cropping enterprises on the alluvial flats would allow encroachment of the saline aquifers onto prime agricultural lands.

Baldry

Initial research by the University of NSW shows that the highest groundwater salinities have been measured at bores located towards the top of the hill at the Baldry site, with the freshest around the saline scalds.

This finding is contrary to the underlying assumptions behind the causes and processes of dryland salinity and is the focus of ongoing research.

Spring storms, such as in October 2004 and November 2005, dominated the water and salt balance data.

Storms at the Baldry site show processes such as salt export are episodic and land management should target groundcover management to mitigate the effect of intense overland flow which can lead to high salt and sediment export.

The Key Sites project began in July 2005, however, it builds on research work before then conducted by NSW Agriculture, the NSW Department Natural Resources (formerly Infrastructure Planning and Natural Resources) and State Forests.