Climate has a much greater influence on salt and water movement than thought previously, according to the results of a NSW DPI salinity hydrology project.

The effects of the drought on groundwater levels and salt mobilisation have been dramatically revealed by the project, which involves monitoring eight typical upland dryland catchments in NSW.

The project, titled "Key Sites for salinity hydrology and model validation", has been researching the effect of land use and climate on salt and water movement at the eight sites since July 1, 2005.

Previous work at the sites began around 2002.

Two of the eight sites are in the north around Tamworth, three in the Central West, one near Boorowa, one near Wagga and in the Hunter Valley.

Over the last five to six years the results from the sites show interesting trends in the amount of water and salt that has been mobilised and transported.

These results have been dominated by the protracted period of low rainfall that NSW has experienced since 2001, and show explicitly the effect of climate on the condition and state of the natural resources, specifically water and salt.

When the sites were first instrumented, mostly in 2002, three had streams draining from the catchments that were either permanent or running most of the time.

Four of the sites had streams running most of the time or streams that run after rainfall.

However, over the period of observation from 2002, the permanent streams have dried up and only run after rainfall, and some of the other streams have not run for three years.

This change in the nature of the streams also affects the amount of salt that is drained from the sites.

The reduced rainfall has meant much less salt is being mobilised and drained into the streams.

This change in stream flow corresponds to decreases in the groundwater level.

The groundwater levels at the Livingstone Creek site have dropped nearly three metres since 2002.

As there has been no change in land use at this site it can be assumed that climate has been driving this trend.

At the Boorowa site, a change in land use in 1998 from cropping to perennial pastures has seen a similar groundwater response, but there is scientific evidence that this is due to a combination of both land use change and climate.

At some of the other sites, groundwater has remained stable over this period, indicating that at these sites there is not such direct connection between climate, land use and groundwater response.

These measured results concur with modelling results from the 2006 NSW Salinity Audit which show that climate has a much greater influence on salt and water movement than thought previously.

The long-term nature of this research sheds light on how these landscape processes occur and the timescales needed to understand the effects of both climate and land use on salt and water movement.

As we move into a period of lower rainfall as predicted by changes to climate, this research will help underpin the investment decisions in terms of policy and on-ground works for improved natural resource management.

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

Some sites commenced in 1994, while the majority of the sites began in 2002 and 2003.

Contact David Mitchell, (02) 6391 3852, david.mitchell@dpi.nsw.gov.au