Lake
Corangamite, Australia’s largest permanent saline lake, is a terminal lake –
one of nine comprising the Western District Lakes Ramsar site - that fluctuates
in depth and salinity in response to the prevailing climate. Since the
1950s when the lake reached its highest recorded level of 118m AHD, there has
been a steady decline to below 113m AHD. The corresponding decline in the
lake biota includes the loss of submerged macrophytes, fish, and a decline in
the diversity and abundance of invertebrates. The euryhaline Australian Brine
shrimp, Parartemia zeitziana, formerly recorded infrequently during drought
periods, is now consistently abundant.
Waterbirds have varied greatly in diversity and abundance with the lowest
counts being recorded in the periods of highest salinity. The
construction of the Woady Yallock diversion scheme in the 1950s to prevent
flooding of agricultural land is a major factor in the decline. Climate change
predictions indicate a drier future for the lake.
To address the lake’s deteriorating condition, the Western Sustainable Water
Strategy calls for the diversion scheme to be “re-managed” to return water to
the lake and to assess the operation of the scheme in 2022 in response to
predicted and observed climate patterns. This presentation examines
preliminary modeling, which indicates that a median climate change scenario is
equivalent to the continued operation of the scheme. The results of
Integrated Quantity and Quality Hydraulic Models are used to consider the
predicted environmental consequences of a range of alternative management
scenarios.