Threat to Lake Macquarie
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What is the biggest threat to
This week I will look at a question
that I am constantly asked, by people who are concerned
about the long-term health of the Lake - "What
is the single biggest threat to Lake Macquarie?"
The answer is simple, stormwater run-off, containing
sediments and nutrients. Understanding the causes and
effects of sedimentation is more complex.
The Lake Macquarie Project Management Committee has
adopted a strategy of community education and works
higher up in the catchment (not directly within the
Lake itself) to slow down the accelerated sedimentation
and nutrient enrichment of Lake Macquarie.
This strategy aims at solving the cause of the problem
instead of the effects, to achieve long-term sustainability
for the Lake.
The objective of community education is not to apportion
blame for stormwater run-off to any community sector.
Rather, by understanding the nature of the impacts we
have on the Lake ecosystem, we might be better equipped
to find ways to lessen the effects associated with urban
development on the edge of sensitive environmental areas.
It should be clear that the objective of community
education and works is to SLOW DOWN the sedimentation
of Lake Macquarie, not to stop it completely. Sedimentation
is a natural process that is sped up by human impacts.
While it might be many thousands of years, Lake Macquarie
actually has a limited lifespan and theoretically it
will eventually fill-in completely through natural processes.
The main way that we speed up the sedimentation process
is through stormwater. It might sound strange, but our
stormwater management systems have become so efficient
at moving water away from our urban areas that they
are damaging the Lake.
In days gone by, stormwater would travel into the Lake
more slowly, through naturally vegetated drainage lines,
wetlands and creeks. Along this journey, sediments and
nutrients were filtered and removed naturally through
a mixture of physical, biological and chemical processes.
In modern times, concrete drainage lines carry stormwater
much quicker and in greater volumes. The missing ingredient
is the natural filtration that makes the water entering
the Lake clearer and cleaner.
We are now faced with a major shift in thinking in
the planning of modern urban development. Instead
of filling in wetlands, replacing natural vegetated
drainage lines with concrete versions and other hard
engineering structures, we are incorporating natural
systems into our urban areas. We are also recreating
natural systems like wetlands and vegetated drainage
lines in an attempt to mimic natural processes. The
result will be a slowing down of sedimentation and
nutrient enrichment and a cleaner, longer life for