Beachmere Lake

The lake is an artificial stormwater feature and provides an environment for fish and marine life. However, there is limited opportunity for fish to migrate out of this artificial system.

Council is working with an appointed fish management consultant to measure the fish population in the lake (number of fish and species), tracking changes over time. This will involve measuring the fish population in the lake several times over the next three years, starting in January 2024.

Council’s consultant will complete the fish surveys via boat and canoes, utilising various sampling equipment (such as underwater cameras and nets) during daylight hours on weekdays.

From time to time the sampling team may visit the lake outside of these times to undertake surveillance, if required. In addition to the fish surveys, other aspects of the lake, including water quality, will be monitored during the survey period.

The goal of this sampling program is to develop an enhanced understanding of the range, number, size and growth rates of fish in the lake. This will assist Council to develop appropriate management approaches that minimise the risk of future fish kills. 

The replacement of the revetment wall around Beachmere Lake has been completed. The timber wall was replaced with durable marine grade sheet pile with a concrete capping. The turf area around the revetment wall and newly planted trees around the lake have been included in a high maintenance phase whilst establishing.

Inflow

The water intake from the sea is located along Kunde Street. The sea water only enters the lake through this pipe system when the tide level is 0.5m above mean sea level.

The combination of the size of the inlet pipes together with activation on the top part of the tide is designed to ensure the water entering the lake is sufficient to allow flushing, however is not so much that it causes the level of the lake to rise and impact on nearby homes.

Outflow

The outflow from the lake is located at the northern end of the lake and is controlled by a weir system. This system allows water to flow back to the sea via underground pipes for the period when the tide levels are below 0.5m.

The intake and out-take pipes operate continuously, responding to each high tide. Minor fluctuations in water level within the lake occur in response to tidal cycles (typically 100-150mm rise and fall per tide).

Stormwater overflow weir

Stormwater drains (for example curb side gutters) in the surrounding residential areas also flow into the lake.

To cater for stormwater input into the lake during and after rainfall events, a stormwater overflow weir is provided at the southern end of the lake. If, due to rainfall events, lake levels exceed 0.8m, excess stormwater is discharged via this overflow. The overflow weir has been specifically designed to prevent high tide water entering the lake from the mangrove area south of Kunde Street. If water was to enter the lake from this location, impacts to homes may occur. 

Tidal exchange system 

The existing tidal exchange system was designed to control lake inflows and outflows. The pipework carrying the tidal water has been inspected and cleaned to remove the build-up of growth and restore the hydraulic efficiency of the system.

The inlet and outlet structures of the tidal exchange system have been upgraded and tidal valves replaced to provide better control of the exchange system and improved maintenance access to ensure long term efficiency of the system.

Sediment removal

The desilting work at Beachmere lake is now completed, with new turf reinstated within the park.

Desilting the inlet of the lake is a scheduled maintenance task to remove excess build-up of sediments around the inlet and improve water movement through the system.

A water quality buoy is located within the lake.

This buoy sends information on the quality of the water electronically to Council, including data on lake water levels, dissolved oxygen concentration, pH and temperature. In addition, an alarm system has been set up to alert Council to conditions that could potentially result in poor water quality.

Aerators (bubblers) are installed in the lake to assist with water circulation, aeration and the mixing of salt and fresh water.

The aerators produce micro bubbles that enable greater oxygen exchange into the water of the lake, whilst continuing to provide a physical mixing function. The aerator system pumps air into the lake. By adding air, it supports the aquatic ecosystem of the lake, especially during times of low dissolved oxygen.