Perennials not the answer in Gumble

Research in central NSW shows it is risky to assume that replanting perennial species in the surrounding local catchment will always fix a salinity problem.

At a recent field day at Gumble, local farmers and Catchment Management Authority advisors were told of the findings of integrated studies which examined recharge and discharge of saline water from the Gumble catchment.

One study examined how we can better manage land that has already become salinised, and the other investigated the cause of the Gumble salt scald.

The first study, part of the 'Sustainable Grazing on Saline Lands’ initiative of the Cooperative Research Centre for Salinity, is conducting research on a saline scald and investigating the impact of pasture improvement on the movement of salt and water to the stream and on livestock performance.

A second study found that the saline scald at Gumble is caused by groundwater which originates outside of the local watershed.

This work, undertaken as part of the NSW Department of Primary Industries’ Key Sites project and funded through the National Action Plan, is looking into the impact of land use on salt and water movement at a paddock and farm scale.

DPI salinity researcher David Mitchell says erosion has filled up a stream at the base of the catchment and is stopping saline water from escaping.

The slopes of the small sub catchment immediately surrounding scald, which contain naturalised pasture and some annual crops, have been found to be contributing fresh water to the creek that drains the catchment.

 “If perennial pastures and trees were planted on them, then this is likely to reduce the runoff of fresh water and decrease stream flow, resulting in the stream becoming more saline.”

Key Sites researchers have examined the hydrology of the catchment and found that groundwater contributing to the scald is flowing in the opposite direction to what was expected.

“If you stand near the scald it is logical to assume that the groundwater is coming from the surrounding cleared hills, but we have found that the groundwater actually flows in the opposite direction.

“The groundwater flows from the scald towards the surrounding hills, a clear indication it is not a local system and the source of the water is outside the catchment.”

Dr Mitchell said geology is a major factor in assessing the causes of salinity in the Central West, an area known to geologists as the Lachlan foldbelt.

“Because of the folding of the sediments, water tends to follow folds and the pathways are not as obvious as you’d think”, he said.

Early in the day, CMA staff and farmers were asked to look at the surrounding catchment and offer opinions as to the causes of the saline scald and the steps that could be taken to address it.

Participants agreed the findings challenge some of the commonly accepted strategies for managing salinity and that a good understanding of local hydrology is needed before funds can be invested to fix the problem.

 

Correction – ‘Fencing saline land’ article

Some comments in an earlier article about the benefit of fencing off saline land were based on an incorrect interpretation of research findings. The article, titled ‘Fencing saline land reduces salt runoff’, may have given some readers the wrong impression about the findings of this research.  For additional information contact Peter Regan peter.j.regan@dpi.nsw.gov.au