The other major source of salinity is from the Jemalong Irrigation area, which has effectively killed Bogandillion Creek to as far as Bogandillion Swamp. This irrigation area may also impact on Lake Cowal in the next 10 years.

The MDBC Audit (1999)1 has estimated trends in the quantity of salt (tonnes per year) mobilised to the land surface over the next 100 years. Based on these trends, Lachlan River salt could increase from 710,000 tonnes in 1998 to 1.78 million tonnes by the year 2100!

The MDBC study (1999) estimated that much of the
salt that is mobilised does not go to the sea, but onto irrigated areas or floodplain wetlands. One suspects that in the Lachlan River’s case, most of this salt is accumulating in the major wetlands such Booligal and in the terminal point of the Lachlan and the Murrumbidgee, the Great Cumbung Swamp (featured on the front cover of this Journal)

Little is known about the long-term effects on these wetlands, but I would suggest the Lake Eyre basin is a grim warning for the future.

According to draft Australian and New Zealand guidelines for fresh and marine water quality, an increase of 500 EC in salinity is given as an ecological warning with possible loss of species biodiversity. Invertebrates and aquatic plants may be salt-sensitive to levels over 1500EC while 3000EC is likely to be lethal. Tadpoles and amphibian egg-masses are also sensitive indicators of salinity increases in wetlands. In some months the Lachlan already exceeds these figures.

Salinity will get worse in the Lachlan Valley — requiring releases from Wyangla Dam as a stopgap measure to maintain acceptable salinity levels. In 1999 when salinity levels at Cowra reached 767EC, additional water was released from Wyangla Dam for salinity management between 8-30 June and 1,012ML of Environmental Contingency Allowance was used.

The use of water for salinity dilution will become more critical in the future management of the River — however, this practice can only be considered ‘crisis management’ as at some point in time, Wyangla will not hold enough quality water to maintain dilution flows. The government needs to treat the salinity problem as a natural crisis.

This requires hard decision-making on:

o stopping of further land clearing

o changes in land management practices and

o rehabilitation of much of the Lachlan Floodplain

Areas of severe salinity around Boorowa and Forbes should be taken out of production and replanted through native revegetation or agro forestry and no further clearing should be allowed in the upper/middle Lachlan. Extensive tree planting projects should be implemented to revegetate much of the upper Lachlan slopes.

To not make these hard decisions will place at risk the prosperity of future generations in the Lachlan Valley, and jeopardise the future of the natural landscape and its dependent biodiversity.