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Close Glossary

Algal blooms - The temporary rapid growth of algae in water. During the early part of the growing season an abundance of nutrients in the surface waters combined with an increase in water temperatures, allows algae to rapidly multiply, until one nutrient becomes scarce or limiting, usually nitrogen. The phase of rapid growth is followed by the algae dying off very quickly and it rises to the surface of the Lake forming a green scum. The decomposing algae consume large quantities of oxygen dissolved in the water causing the waters to become anaerobic, killing most of the aquatic life (primarily fish). These are often more prominent in shallow areas and enclosed bays, where there is often high nutrient input from nearby urban development.

Catchment - A large area of land which catches and collects water for a river, stream, creek or lake.

Constructed Wetland - Constructed wetlands are purpose built structures, utilising the predominantly natural materials of soil, water and biota, which perform the desired physical, chemical and biological processes and functions of natural wetlands. Constructed wetlands are designed primarily for improving the quality of stormwater runoff by filtering out sediments and nutrients before they enter the lake.

Delta - The flat area, normally fan shaped, at the mouth of some water courses and creeks where the main stream divides into several distributaries. Examples of deltas can be found throughout Lake Macquarie, such as Five Islands at Speers Point. Deltas occur where there is an accumulation of sediment deposited in the Lake. This happens when fast flowing waters meet with areas of still water. While the fast running water is able to carry sand and sediments along with it, this material is deposited once the velocity of the current slows. The sand and sediments are dropped to create the delta. Wave action and currents may work with sedimentation to shape a delta.

Dredging - Dredging is the removal of sediments from the bed of the lake. Dredging is normally only carried out to remove excessive sediments that have entered the lake as a result of stormwater runoff and pose a threat to the health of the aquatic ecosystem. Dredging is sometimes carried out for navigation purposes.

Estuary - Semi-enclosed coastal body of water which has a free connection with the open sea, but within which the salinity level of the ocean is considerably diluted by the addition of fresh water brought in by a river system. 

Eutrophication - The process of nutrient enrichment of an aquatic system. In water environments like Lake Macquarie, occurrence of eutrophication has increased in frequency due to urban development and agricultural production. The nutrients accumulate at a greater rate than can be recycled by decomposition or used in photosynthesis, often resulting in algal blooms.
Foreshore Stabilisation & Vegetation - These works are carried out to address foreshore erosion on public lands. It normally consists of construction of a natural sloping beach and vegetation with endemic species. The vegetation also provides a filter for runoff into the lake. Sometimes in very exposed areas a row of rock work may be used behind the beach, however endeavours are made to avoid a hard visual impact and natural methods are used as much as possible.

Groyne Construction - Rock "finger" groynes extend into the lake at 90° to the foreshore to address erosion problems. They are only used when other methods would be unsuccessful and access to a natural foreshore is required.

Littoral vegetation - Vegetation in the area around the edge of the Lake.

Nutrient cycle - The constant transfer of essential nutrients from living organisms to the physical environment and back to the organisms in a cyclical pathway. This sequence is achieved by the physical processes such as weathering and/or biological processes such as decomposition.

Riparian vegetation - Vegetation in areas around the edge of streams.

Sedimentation - The deposition of sediment. Sediment in the soil particles and rock fragments transported and deposited by the action of rivers, glaciers, sea and wind.

Stormwater Pollutant/Sediment Traps - These traps are normally commercial, pre-caste, below ground devices or open, caste in-situ concrete boxes that capture or filter coarse sediment and litter from stormwater flows. They require routine maintenance to remove the accumulated sediment and litter that has been prevented from entering the lake.

Vegetated Swales - These swales mimic natural watercourses and the base may have some rockwork, ripple ponds and vegetation. The plants put oxygen into the water and act (in a limited way) like a constructed wetland to assist in filtering out finer sediments and nutrients. They are normally used in conjunction with a sedimentation basin or stormwater pollutant trap.