Processes Impacting on Lake Macquarie

Threat to Lake Macquarie
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What is the biggest threat to Lake Macquarie?
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 Lake Macquarie.

 

Editiorials
Channel Challenges
Channel & Water Quality
Constant Change
Seagrass
Seawalls
Threats to the Lake
Vegetated Swales
Water Sensitive Urban Design
Wetlands
Wrack & Ruin
Introduction