Lake Ainsworth

In 2018 Council engaged Hydrosphere Consulting to prepare a CMP to provide a long-term strategy and management actions for Lake Ainsworth. The CMP was prepared in accordance with the NSW Coastal Management Act 2016 and the NSW Coastal Management Manual and was one of the first CMPs to be certified in NSW. The Lake Ainsworth CMP contains 29 actions in total which are to be carried out within a ten-year timeframe. These actions cover various management issues including:

• Water quality
• Sediment management
• Bank erosion
• Catchment management
• Cultural heritage
• Flooding
• Flora and Fauna
• Community uses
• Education

Action 1 – Trial modifications to artificial aeration

complete 

Lake Ainsworth - Action 1 - Trial Modifications to artificial aeration - Report (pdf)

The Phase 1 monitoring trial was carried out during the summer months of 2022 and was intended to continue through autumn, however autumn sampling was not carried out due to extremely high lake levels following the February and March floods. Phase 2 of the monitoring trial commenced in September 2022 and will run until May 2023.

This project is designed as a trial over a two-year period to test the effects of modifying the current aeration program on lake water quality and specifically the incidence of blue-green algae blooms. The following modifications are being undertaken in the trial:

Phase 1 aerator trial – results

Phase 1 of the trial indicated marked improvements in water quality observed with 24-hour operation of the aerator.

• At the conclusion of the trial nutrient concentrations measured in the lake and particularly at the surface of the lake had decreased substantially.
• Phosphorus showed the greatest reduction, while the overall reduction in nitrogen was minor. Chlorophyll a and cyanobacteria concentrations were also reduced during the 24-hour/day operation.
• Reductions in nutrient and particularly bioavailable phosphorus concentrations observed are likely to have contributed to reduced levels of cyanobacteria and algae, although the climatic conditions this summer (i.e., above average rainfall and cloudy, cool conditions) are also likely to have created conditions less favourable for algal growth.

Phase 2 aerator trial – September 2022 - May 2023

• Step 1. Aerators to be operated 24 hours per day over the Spring/Summer season (as Phase 1 trial showed improvements to water quality). 
• Step 2. Reporting and analysis of monitoring data collected.
• Step 3. Provision of a final report with recommendations for future management of the aerator regime in the lake, based on the results of the data collection and analysis.

Actions 3 and 10 – Beach nourishment and erosion protection

March 2022 - late 2024 

Council was successful in obtaining grant funding under the Crown Reserves Improvement Fund (CRIF) to undertake works surrounding the lake in areas that have been heavily eroded through natural factors and human use. Eroding banks and exposed tree roots are creating uneven footing with trip hazards and causing damage to tree health and bank stability.

The project aims to take the following approach:

• Carry out beach nourishment through the placement of sand along priority foreshores to address the loss of beach areas.
• Establish a beach retention sill where required to stabilise steeper beach gradients. This will consist of a row of large sandbags installed underwater to act as a retaining sill to reduce the downslope loss of sand.
• Backfilling of tree roots. This measure is an extension of the beach nourishment and will re-establish soil levels over tree roots that have been exposed due to continued erosion.
• Riparian vegetation, fencing, and access management. This measure is part of a continuing strategy to ensure that vegetation around the lake is healthy and resilient, and the foreshore is managed to reduce human impacts that cause erosion.
• Stormwater management will be addressed and will be vital in ensuring foreshore erosion is minimised.

Actions 4, 9 and 22 – Riparian vegetation enhancement for erosion control and educational signage

March 2022 - late 2024 

This project has been slightly amended in response to the impacts of the severe weather and flooding experienced in the Ballina Shire in early 2022 leading to the lake levels being higher than normal and access to riparian area being inaccessible. This project will begin with rehabilitation of the dune areas at the Eastern side of the lake. Once water levels have receded this project will follow woks outlined in Action 3 of the CMP with the Southern and Eastern foreshore rehabilitated and revegetated in a way that offers greater erosion protection while managing adequate access for the community.

Issues to be addressed:

• Foreshore erosion of the lake
• Foreshore accessibility and public safety
• Stormwater impact
• Poor riparian vegetation condition
• Terrestrial weeds
• Decreased amenity and enjoyment
• Reduced aesthetic quality of the foreshore
• Educational resources to foster understanding, respect and stewardship for the Lake.