Greg Summerell collects water samples from rising stage sample bottles that are arranged vertically on a staff. Once the water level goes over a bottle it fills with water and, once full, a one way valve secures the sample. Water samples are used to finger print the types of salts and water that entered the stream during different stages of rain.

A field study that has created a better understanding of the way salt travels from the landscape to the stream is applicable throughout the upland Murray-Darling Basin.

In the Livingstone Creek catchment, an area of 43 square kilometers, located 30 kilometres southeast of Wagga Wagga, has been monitored since 2000. In this catchment the processes of dryland salinity are typical of upland alluvial landforms in the Murray-Darling Basin.

The study by Greg Summerell from the Department of Natural Resources, prepared for his PhD through the University of Melbourne, reveals salinity movement in streams differs markedly between major landforms.

"Dr Summerell’s study provides a substantial advance on previous knowledge and has changed the way salinity modelling is conceptualised," Vic Shoemark, a salinity technical officer for NSW Department of Primary Industries (DPI) at Wagga Wagga said.

Areas of salt-affected flatter alluvial landforms are potentially major salt sources in the upland Murray-Darling Basin.

Dr Summerell’s major finding indicates that in sloping landscapes during rain, measurable stream salinity shows the classic response, but is quite different in streams that flow through flatter alluvial valleys.

On the hills, there is an initial spiking of salt movement in the stream when rain falls. This is the result of flow rapidly washing across the landscape mobilising surface salts ("first flush"), which then later dilutes as more surface run-off water contributes to stream flow.

However, in the flatter alluvial valleys, the salt response goes with the flow - as more water flows, salinity increases and when less water flows, salinity decreases; here salt movement from the land to the stream is governed by soil water contributions.

Rainfall infiltrates rapidly through the alluvial soils and washes salts stored in them through the soil profiles to the stream.

Usually, leakage across all parts of the landscape is controlled by changes in land use and management; in cropping areas, the introduction of high water-using perennial pastures is usually recommended.

"However, in the Livingstone Creek catchment, saline water moves down the valley through the meta-sediments geology and amelioration of salinity requires a different approach to what has been the norm," Greg Summerell said.

Maintaining the leakiness of the alluvial landform flushes the salt from the soil profile, preventing it from becoming concentrated and therefore reducing a land salinisation problem.

To prevent salt mobilizing, and concentrating in the alluvial landscape, it is necessary to control recharge in the headwaters of the meta-sediment geology.

The results at Livingstone Creek have been measured by a detailed network of monitoring equipment - seven stream gauging stations measuring flow and EC, eight-soil moisture stations automatically monitoring at four depths (0.6, 1.6, three and four metres), 21 automatic groundwater monitoring locations, two units monitoring evapotranspiration from crops and pastures, and a weather station.

Many State and Federal salinity modeling tools, particularly those used to simulate land management changes, are being improved by the new knowledge of processes of alluvial landform salt and water movement into streams.

The Livingstone Creek field site was established in 2000, and since 2005 has been one of eight high priority dryland salinity locations in NSW being studied in the Key Sites project led by the DPI and the Department of Natural Resources.

The Livingstone Creek project has attracted new research partners and the interest of other organisations, including the University of Melbourne, University of Adelaide, CSIRO Land and Water, eWater CRC, the former CRC for Catchment Hydrology.

Contact: Vic Shoemark, Wagga Wagga 02 6938 1949, Greg Summerell (Department of Natural Resources), Wagga Wagga, 02 6971 4121, Tony Bernardi, Queanbeyan, 02 6297 1861.