The Southern Grampians Shire
Council (SGSC) engaged GHD to develop an Action Plan to improve
water quality in Lake Hamilton in Australia. The overall aim of the
Action Plan was to manage and prevent high levels of Cyanobacteria
(blue-green algae) and Escherichia coli (E.
Lake Hamilton is located in western Victorian, Australia and is
fed by the Grange Burn, urban stormwater and overland flow.
Recurring high levels of Cyanobacteria and E. coli has resulted in
the SGSC erecting warning signs to deter the use of the lake due to
potential public health issues.
The most significant finding of the Action Plan was that Lake
Hamilton has undergone a long period of eutrophication. The main
factor contributing to Cyanobacterial blooms was excessive
nutrients entering the lake from stormwater and the Grange Burn.
There is also a large bank of nutrients contained within the lake
Short to medium-term management actions include the use of
chemicals (as algicides), microorganisms to consume nutrients, and
dyes to attenuate sunlight and discourage algal growth. However,
these options may pose risks to the lake and further downstream in
the Grange Burn. There is also a large financial cost associated
with their use.
Artificial aeration was another potential short to medium-term
action aimed at breaking down water column stability
(stratification which promotes algal growth) and creating
oxygenated conditions in the water column to limit the release of
nutrients from the sediment. Currently, there is no evidence of
seasonal stratification so this action can only be considered
following a more comprehensive investigation.
Dredging of the lake sediments was considered to reduce the pool
of nutrients. The large financial costs associated with dredging
and the impacts on the Lake ecosystem resulted in this action not
Ultimately, Lake Hamilton requires long-term management actions
to address the problem of eutrophication. Such actions should be
aimed at reducing nutrient inputs from the Grange Burn. Significant
catchment management, such as the introduction of riparian buffer
strips, stabilisation of riparian zones and improved farming
practices are required to limit nutrient entry and further
eutrophication. Maintenance and enhancement of macrophytes was
identified as an important action as they have the capacity to
reduce nutrients. Reduction of nutrients could also be achieved by
construction of a treatment wetland upstream of the Lake and by
introducing stormwater treatment swales.
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