Processes Impacting on Lake Macquarie

Constant Change
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Change in Lake Macquarie is a process of continuous evolution. It is natural, constant and in many cases desirable. The challenge we face, is to manage the rate of change, which has been accelerated by human activities, to achieve our goal of a healthy and functioning ecosystem.

The environment will never return to 'how it used to be', because of the natural evolution that is always occurring. The Lake is constantly ageing and has a limited life span. In fact, even without human intervention, Lake Macquarie would eventually fill in through natural processes. However, maintenance of a healthy ecosystem is possible by reducing the quantity of nutrients and sediments entering the Lake with stormwater.

The most obvious signs of this infilling occur around the mouths of the larger creek systems. When the velocities of the creek slow as the waters mix with the lake, sediments drop out to form extensive delta areas. For example, the area known as Five Islands at the mouth of Cockle Creek, has filled in so rapidly it is barely possible to distinguish the former five islands.

In geological terms Lake Macquarie is still quite young, formed only 6,000 years ago. Many parts of low lying suburbs such as Dora Creek, Blackalls Park, Speers Point and Teralba, located nearby to creek systems were actually part of the Lake only a few thousand years ago.

Prior to Europeans settling in Lake Macquarie, the flow of sediments into the Lake was estimated to be at a rate of approximately 6,600 tonnes per year. By 1983, the then State Pollution Control Commission estimated that sediments were flowing into the Lake at a rate of approximately 75,000 tonnes per year. With this type of exponential increase in sediments and nutrients, it is easy to see why Lake Macquarie became such a stressed environment.

Since the early 1990's, we have learnt a lot about the natural systems within our environment and the role they play in maintaining balance and wellbeing within the ecosystem.

We have also identified some of the many contributors to increased sedimentation and nutrient enrichment and through community awareness and behavioural change within the catchment, we have had some success in addressing the problems.

In 1998 the Lake Macquarie Task Force established by the NSW Premier estimated the flow of sedimentation into the Lake to be approximately 57,000 tonnes per year and some believe that it has since reduced even further. It is a trend we need to continue.

Supporting natural filtration systems like wetlands and vegetated areas (especially around creek banks and in drainage lines) is important as they remove contaminants from stormwater to reduce the stress on the lake.
The Project Management Committee has funded a number of projects which re-introduce natural processes back into the environment. These include the construction of wetlands, sedimentation traps and vegetated drainage swales. While these projects will never fully replicate the natural processes, by mimicking them we can help the environment to manage natural change more effectively.

 

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