Botanica Park lake Bundoora

Background

• Botanica Park lake is located 16km north of Melbourne in the suburb of Bundoora.
• The lake was built in 1999.
• The lake is divided into two sections
  • Northern lake (Upper lake)
  • Southern lake (Lower lake)

Northern lake

• Stormwater enters the lake from a relatively small catchment (approximately 100 house roofs and road surfaces)
• Stormwater is treated through a Gross Pollutant Trap (GPT) which removal leaves and large litter items
• Stormwater then enters the northern lake where aquatic plants help to remove excess nutrients from the water.
• The northern lake is shallow (0.5m to 1.5m depth) and is shaded by River Red gum trees.

Southern lake

• Stormwater enters the southern lake (from the northern lake) during rain events.
• A weir underneath a footbridge separates the two lakes.
• The southern lake is deeper, has steep embankments and contains large submerged stands of eel grass as the predominant vegetation.
• During rain events, water will exit the southern lake in a raised stormwater pit (underneath the decking on the east of the lake). Water travels via a Melbourne Water drain and empties into Blau Street Park further south, before entering the Darebin Creek.

Water for All Strategy 2020-2030

• The City of Whittlesea has adopted the Water for All Strategy 2020-2030 which identifies cleaner waterways as one of five key outcomes for success.
• Many of Council’s existing water assets need to be renewed because they are not providing adequate stormwater treatment and are therefore compromising the health of local waterways.
• In addition to treating stormwater, water treatment assets improve amenity values, assist with urban cooling, and provide a safe habitat for birds, frogs and other native animals.

History at Botanica Park

• June 2017 – Botanica Park Lake Masterplan.
• Feb 2018 - Avian botulism outbreak early 2018 resulting in more than 40 bird and fish deaths at lake. Lake fenced off and community educated about not feeding ducks. Previous duck population at lake was 200.
• Mar 2018 – Park upgrade. New playground installation.
• Aug 2018 – Engeny investigation into water quality and treatment options.
• May 2019 – Peter Homan audit of frog habitat improvement opportunities.
• Aug 2019 – Aquatica Environmental audit of biota in lake.
• Feb 2020 - Commencement of revegetation works at Botanica Park Northern Lake.
• June 2020 – Revegetation of Botanica Park Northern Lake with NatureLinks.
• June 2021 – Removal of litter and filamentous algae (Re-Veg Works).
• June 2021 – Aeration fountain installation.
• July 2021 – Community Planting Day with the Whittlesea Youth Environment Action Group and residents from the community.
• Dec 2021 - Planting of aquatic vegetation in northern lake to assist with nutrient removal.
• Jan 2022 - Removal of filamentous algae from northern lake.

Challenges with Lake

The following issues were identified at Botanica Park.

Northern lake

• Sedimentation pond needs desilting (every 5 years). The next desilting operation is scheduled for 2022.
• Large numbers of introduced Mosquitofish (Gambusia holbrooki) are present. This species has been implicated in the reduction of frog populations. Mosquitofish are known to predate on frog eggs and tadpoles. Mosquitofish can only be removed by draining the lake and euthanising all individuals. Mosquitofish give birth of live young, so draining the lake (lake must be free of all standing water) is sufficient to remove all mosquitofish. There is a risk that large rain events may allow for new mosquitofish individuals to enter the lake.
• No frogs present at the lake. Frogs exist at other sites around Botanica Park lake. Common Eastern froglets (Crinia signifera) and the Spotted Marsh Frog (Limnodynastes tasmaniensis) are very common on McKimmies Rd, Bundoora. Frogs may not be present for two reasons:
  • Excessive predation by mosquitofish
  • Insufficient protective habitat for frogs around the waterbody, including on land.
• No small birds present within park that are typically associated with waterways (e.g. Superb Fairy-wren - Malurus cyaneus, Spotted Pardalote - Pardalotus punctatus) due to a lack of bushy cover vegetation.
• Macroinvertebrates populations are very low and indicative of very poor water quality based on the SIGNAL analysis. Poor macroinvertegrate diversity is attributed to:
  • stormwater pollution (e.g. hydrocarbons, pesticides, heavy metals) and other contaminants in stormwater
  • excessive predation by mosquitofish and other non-native fish
• Lack of terrestrial vegetation and refuge sites to provide perennial diurnal (year-round daytime shelter) and non-breeding shelter sites for frogs and other fauna.
• Herbicides are regularly used, and it is difficult to determine if ‘frog sensitive’ herbicides are being correctly applied.

Southern lake

• Evidence of duck feeding (in the past)
• Domestic ducks dumped on site. Domestic ducks are removed from the lake by Council and re-homed. Domestic ducks are not suitable for waterbodies in parks because they encourage people to feed them and they may also try to mate with native domestic birds.
• No emergent vegetation around perimeter of lake. Emergent vegetation provides habitat, nesting material and food sources for birds and other animals. Vegetation also helps to remove nutrients from the water which helps to reduce the growth of algae.
• Introduced fish in lake – Carp, Mosquitofish
• No frogs or habitat refuges for frogs
• Excessive amounts of unsightly floating litter in lake
• Steep embankments which limits entry and exit of frogs and other small fauna
• No island within lake as a refuge for aquatic species. Although there is a small water fountain that operates during the day and provides a small dry platform at night.
• Avian botulism outbreak in early 2018. The water quality has since improved and Avian botulism has not re-occurred.
• Filamentous algal bloom in 2021. Filamentous algae is a difficult algae to eradicate. More aquatic vegetation in the lake that can shade out the water and remove excess nutrients in the water will help to reduce the growth of filamentous algae. The current treatment used at this lake is to remove the algae by hand (contractors using boats). The addition of an agent called Aquaritin may also help. Aquaritin acts to promote the growth of freshwater diatoms.
• Turtles living in lake can accidentally fall into stormwater exit drain. The exit drain needs to be re-engineered so that turtles cannot fall into it.

Animals

Birds identified in Park

Food complements

Fruits	Fats
Orange	Butter
Pear	Pie
Apple	Ice cream