Botanica Park lake Bundoora

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This web site is an experiment with local students, residents and public agencies to see if the health of Botanica Park lake can be improved by participative governance and information sharing between agencies. In a low carbon and resource constrained future we will all need to explore better methods of engagement and knowledge sharing to protect our communities and the natural environment.

News and Events

Planning for a Community Planting Day during the school holidays in lake June-July 2022 - covid permitting. More than 2000 terrestrial plants will need be planted around the northern lake to provide habitat for small birds and frogs. We are also hoping to run a Waterbug event so that you can see what tiny animals live in Botanica Park lake and other nearby lakes. A diverse population of waterbugs are a good indicator of a healthy waterbody.

Collection of waterbugs from a healthy waterbody.

Background

  • Botanica Park lake is located 16km north of Melbourne in the suburb of Bundoora.
  • The lake was built in 1999 and was originally intended to provide a habitat for frogs, especially the endangered Growling Grass frog (Litoria raniformis).
  • It has a clay lining (300mm thick) to prevent water seepage and a water residence time of 35 days (estimated using MUSIC). The recommended water resident time is 20-30 days (Melbourne Water).
  • The lake is divided into two sections
    • Northern lake (Upper lake)
    • Southern lake (Lower lake)

Photo of the threatened Growling Grass frog captured during a wildlife audit 14 Dec 2021. These frogs were once very common all throughout the municipality. It is believed that urban development, pollution, introduced animals, loss of habitat and the chytrid fungus (Batrachochytrium dendrobatidis) have caused local populations to crash.

Northern lake

  • Stormwater enters the lake from a relatively small catchment (made up of approximately 100 house roofs and road surfaces)
  • Stormwater is treated through a Gross Pollutant Trap (GPT) Botanica Park which removal leaves and large litter items (bottles, plastic, cigarette butts).
  • 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 (Eucalyptus camaldulensis) trees.

Southern lake

  • Stormwater enters the southern lake (from the northern lake) during rain events.
  • A weir underneath a footbridge separates the two lakes. When the northern lake fills it spills over into the southern lake. It is not know if the weir is leaky or if there is a pipe that connects the two lakes directly.
  • 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.

City of Whittlesea 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 of Botanica Park Lake

  • 1999-2000 - Design and construction of the lake.
  • June 2017 – Botanica Park Lake Masterplan published by City of Whittlesea.
  • 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. Duck population successfully reduce from 200 to 20.
  • 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 (Aquatic Technologies).
  • July 2021 – Community Planting Day with the Whittlesea Youth Environment Action Group and residents from the community (6th July 2021) with NatureLinks. Riparian vegetation included Kangaroo grass (Themeda triandra), Slender Wallaby grass (Rytidosperma racemosum), Purplesheath Tussock Grass, Sword Tussock Grass (Poa ensiformis) and Common Sedge (Carex tereticaulis).
  • July 2021 - 2 Male Domestic Mallards removed from Botanica Park southern lake by Nigels Wildlife Rescue service.
  • Dec 2021 - Planting of aquatic vegetation in northern lake by NatureLinks to assist with nutrient removal and to provide habitat for frogs.
  • Jan 2022 - Removal of filamentous algae from northern lake by Reveg Works.

Community Planting Day Botanica Park 6 July 2021

Community Activities

Challenges with Botanica Park Lake

The following issues were identified at Botanica Park lake. Council is working on a Project Brief to help address most of these water related issues over the next 2 years.

Northern lake

  • Sedimentation pond needs desilting (every 5 years). The next desilting operation is scheduled for 2022. Access to the east of the sedimentation pond needs to be grassed so that heavy excavation vehicles can access the desilting site. An area within the park also needs to be defined so that removed silt can be dewatered before being sent away to landfill.
  • 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 protective bushy 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 to control weeds. It is not know if all herbicides are ‘frog sensitive'.

Southern lake

  • Evidence of duck feeding (in the past) which resulted in the pollution of lake water and the build up of nutrients in sediments. This resulted in a disease outbreak which affected both birds and fish.
  • 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 outlet drain. The outlet drain needs to be re-engineered so that turtles cannot fall into it.
  • Turtles also need more emergent vegetation or exposed rocks so that they can sleep at night (head above the waterline) and sunbake when the weather if warm.
  • The southern lake is relatively exposed to the hot summer sun. Additional tree plantings will help to shade the water which will help to minimise algal blooms.

Animals

Our Parks provide homes for many animals. You can help our native animals by:

  • Not feeding any native animals - not even native food mixes. Instead buy a book on birds, install an app on your phone or buy a camera with a good zoom lens (e.g. Canon PowerShot SX70 HS) and learn how to identify these little creatures.
  • Install any of the following apps:
  • Keep dogs on leashes and lock up cats at night (on average cats kill 8 small animals every day!).
  • Plant native plants in your garden. These provide both food and habitat for our native animals. Parks only represent 5% of all the land area in our municipality.
  • No not use any weed killers or fertilisers on your garden (except home compost) because these wash into our waterways when it rains.
  • Install a rainwater tank and use the water on your garden.
  • Ride a bike, walk or take public transport. Many animals are killed or injured by cars and cars are a major source of urban pollution (oils and heavy metals).
  • Report any pollution events to the EPA and also alert Council. Oil spills and other pollutants harm animals and plants.
  • Only wash your car at special car washing stations. Washing cars on the street sends detergents into our stormwater drains and into local waterways.
  • Humans take too much water from waterways. 20% of water is extracted for cities and 70% of the water is extracted for agriculture. This only leaves 10% of the original water for animals. Foodprint Melbourne - How much water is needed to grow Melbourne’s food?
  • Solutions include installing rainwater tanks at home (10,000 litres), diverting greywater to your garden, growing more food at home and installing a waterless composting toilet. See ANU report Troubled Waters Confronting the Water Crisis in Australia’s Cities - Conclusion


Birds

Botanica Park once had up to 200 Pacific Black ducks because they were being fed. Once feeding stopped the number of ducks at the lake dropped to between 10-20. Most of the Pacific Black ducks left, and there are mainly Australian Wood ducks. This population number is acceptable for a lake of this size. As a general rule, we should not feed any animals in the wild. Instead, we should aim to plant more grasses, shrubs, bushes and trees so that animals have all the habitat they need to provide for their own needs.

Red-rumped Parrot Botanica Park lake northern lake 25 Feb 2021

A recent survey of the park in 2021 gives an indication of the diversity of bird species present in the park and also highlights birds that are not present.

Birds in Botanica Park - Small (S), Medium (M) and Large (L)
Common Occasional Not seen in park, present nearby
Australian Wood Duck (L) Willy Wagtail (S) Spotted Pardalote (S)
Pacific Black Duck (L) Little Pied Cormorant (L) New Holland Honeyeater (M)
Rainbow Lorikeet (M) Welcome Swallow (M) Striated Thornbill (S)
Red-rumped Parrot (S) Corella (M) Superb Fairy-wren (S)
Red Wattlebird (M) Galah (M) Silvereye (S)
Rainbow Lorikeet (M) Grey Teal (L) Red-browed Finch (S)
Australian Magpie (M) Black Swan (L) Grey Fantail (S)
Crested Pigeon (M) Australian Shoveler (M)


Most waterbodies provide habitat for a wide range of birds. Some good examples of diversity are present along the Darebin creek within Mun Reserve, Thomastown, Blau St Park, Bundoora and Watson Court Park, Lalor (north of McKimmies Rd). All of these parks have lots of small birds such as:

  • Willy Wagtails
  • Spotted pardalotes
  • Grey fantails
  • Red-browed Finches
  • New Holland Honeyeaters
  • Yellow Thornbills
  • Superb Fairy-wrens
  • Red-rumped Parrots
  • Musk Lorikeets

The arrangement of trees, small bushes, open grasslands and water play a big role in determining what small animals can live in a park. Small birds require bushes and trees that provide a safe refuge from larger birds (e.g. Noisy miners) and food sources (nectar and/or insects). Watch this video from ABC Catalyst (1 Feb 2022) The Secret Lives of Our Urban Birds especially the 40-50 minute mark, to see what happens when the vegetation mix in a park is not favourable to small birds. Most of the examples presented in this program are from Melbourne.

Vegetation for Small Birds

  • Grey Fantail (Rhipidura fulginosa) - a member of the flycatcher family. Catches flying insects with incredible accuracy.
    • Acacia spp.
    • Cedar Wattle (Acacia elata)
    • Sunshine Wattle (Acacia terminalis)
    • Eucalytpus spp. including Argyle Apple (Eucalytpus cinerea)
    • Sheoaks (Casuarina spp.) - also suitable habitat for Willy Wagtails
    • Tea-trees (Leptospermum spp.)
  • New Holland Honeyeater (Phylidonyris novaehollandiae) - prefers open woodlands adjacent to water. Nectar feeder, but also eats small insects.
    • Acacia spp.
    • Banksia spp.
    • Bottlebrush (Callistemon spp.)
    • Hakea spp.
    • Paperbark (Melaleuca spp.)
    • Grevillea spp.
    • Grass Tree (Xanthorrhoea spp.)
  • Spotted Pardalote (Pardalotus punctatus) - very load call for such as small bird. Their beak is specially designed to eat thrips, spiders, moths and caterpillars in eucalypts and acacia foliage.
    • Acacia spp.
    • Eucalypus spp including Argyle Apple (Eucalytpus cinerea) - clumps of these trees will attract thronbills and pardalotes throughout the year because they feed on parasitic insects such as scale.

Bird photos around Botanica Park

Australian wood ducks Chenonetta jubata in Botanica Park

Eastern rosella Platycercus eximius eating grass seeds on a grassy lawn

Musk lorikeet Glossopsitta concinna makes its home in tree hollows nearby in Bundoora Park.

Frogs

There are currently no frogs at Botanica Park lake.

Frog species

Frog species that should be present at Botanica Park include:

  • Common Eastern Froglet - Crinia signifera
  • Spotted March Frog - Limnodynastes tasmaniensis
  • Southern Brown Tree Frog - Litoria ewingi

Spotted March frog - Limnodynastes tasmaniensis in Bundoora 20 Jan 2022

Habitat for Frogs

The aim is to first establish habitat suitable for frogs. Suitable habitat needs to include the following features:

  • Grass and shrubs for protection and shelter.
  • Logs and rocks that frogs can hide under (e.g. railway sleepers and old roof tiles).
  • Access to clean water (not muddy). Water that is muddy has a high turbidity. Clean water has a low turbidity. Water should be clear enough so that you can see to the bottom.
  • No foreign fish (e.g. carp and mosquitofish). If all foreign fish cannot be removed, then the provision of off-stream ponds may provide a safe refuge for frogs.
  • Vegetation next to water to provide habitat (e.g. Poa spp, Lomandra spp).
  • Gentle banks (not steep). Frogs can hop in and out of waterbodies provided that the banks are not too steep or high. This will also benefit the moment of other aquatic animals such as turtles.
  • Vegetation corridors so frogs can travel overland at night between waterbodies (frogs are nocturnal).
  • Protection from cats, dogs and people. Please keep all cat in at night and all dogs on their leash at all times.
  • Diverse and healthy population of waterbugs in the lake water (macro-invertebrates).
  • Site should be free of insecticides and other chemical treatments.

Vegetation for Frogs

  • Common Tussock-Grass - Poa labillardierei - Height 1m. Large tussock. Plume-like flowerheads appear from spring to summer. Prefers moist, well-drain soils.
  • Spiny-Headed Mat-Rush - Lomandra longifolia - Height 1m. Large tussock. Flower spikes appear in spring and summer. Drought tolerant. Provides ground cover around waterbodies.
  • Native Broom - Viminaria juncea - Height 3-4m. Fast growing small tree. Flowers in spring and summer. Prefers shade and moist soils.
  • Hedge Wattle - Acacia paradoxa - Height 2m. Dense shrub with thorns. Flowers in spring. Good bird habitat and also provides protection for frogs.

Plants

To improve the habitat for frogs, birds and insects, the following new plantings are proposed. Two good books for reference include:

  • Plants of Melbourne's Western Plains - A gardener's guide to the original flora. 2nd edition. Australian Plants Society, Keilor Plains Group Inc.
  • Birdscaping Australian Gardens - Using native plants to attract birds to your garden. George Adams.

Suppliers of Native plants

Small plants can be obtained from native or indigenous nurseries as tube stock. Indigenous means from the local area, whereas native means from Australia. Suitable suppliers for home gardeners include:

  • Edendale Farm Nursery, Nillumbik
  • Indigenous plant nursery - Wildlife - La Trobe University

Aquatic plants - Northern lake plantings

Aquatic plants have recently been installed in the northern lake of Botanica Park (10 Dec 2021). Water Ribbons (Cycnogeton procerum) were placed under netting to protect them from ducks and other aquatic birds during their establishment phase. Water Ribbons will gradually spread within the lake. They flower from September to March. These aquatic plants also provide a safe habitat for frogs.

Frog and Small Bird Garden - Proposed Northern lake plantings - East side

  • Gold-Dust Wattle - Acacia acinacea - Height 1.5. 100 plants - Prefers well drained soils. Can tolerate full sun or part shade under eucalytpus trees. Bird friendly habitat
  • Silver Wattle - Acacia dealbata - Height 8-15m. 200 plants - Fast growing tree. Flowers in winter to spring. Prefers moist soils and will tolerate inundation. Bird and butterfly friendly.
  • Black Wattle - Acacia mearnsii - Height 8-12m. 200 plants - Fast growing. Needs a sunny position with well drained soils. Provides food for butterfly caterpillars, and insect and seed eating birds. Bird and butterfly friendly.
  • Golden Wattle - Acacia pycnantha - Height 4-6m. 50 plants - Fast growing. Golden ball flowers appear in winter and spring. Needs dry, well-drained soils. Lives for 7-10 years. Australia's floral emblem. Bird and butterfly friendly.
  • Prickly Moses - Acacia verticillata - Height 2-4m. 200 plants - Prickly shrub. Flowers in winter to spring. Fast compact growth habit. Provides protection for small birds.
  • Silver Banksia - Banksia marginata - Height 4-8m. 50 plants - Small tree with yellow flower spikes in summer and autumn. Once common on basalt soils. Needs moist well drained soils. Bird and butterfly friendly.
  • Sweet Bursaria - Bursaria spinosa - Height 4-6m. 400 plants - Small tree. Small fragrant flowers and thorns on stems. Very hardy plant. Bird and butterfly friendly. Important for the Bright Copper butterfly.
  • Rock Correa - Correa glabra - Height 1-2m. 100 plants - Flowers from May to August. Prefers dry, well-drained soils. Bird friendly.
  • Ruby Saltbush - Euchylaena tomentosa - 100 plants - Ground cover. Fruits with yellow to red berries all year round. Prefers dry and well drained soils. Suitable for rocky slopes.
  • Rosemary Grevillea - Grevillea rosmarinifolia - Height 1.5m. 100 plants - Red and cream flowers in winter and spring. Attracts honeyeaters. Prefers well-drained soils. Bird and butterfly friendly.
  • Hemp Bush - Gynatrix pulchella - Height 2-4m. 50 plants - Fragrant, cream flowers in spring. Prefers moist soils that are well drained. Separate male (larger flowers) and female plants. Prune after flowering to encourage bushy growth.
  • Bushy Needlewood - Hakea decurrens - Height 2-3m. 100 plants - Pink flowers in winter and spring. Prickly leaves. Bird friendly.
  • Purple Coral-Pea - Hardenbergia violacea - Ground cover. 50 plants - Purple flowers from winter to spring. Good ground cover plant. Butterfly friendly.
  • Leptopspermum continentale
  • Wooly Tea-tree - Leptospermum lanigerum - Height 2-4m. 50 plants - Dense shrub with white flowers in spring and early summer. Prefers moist soils. Prune after flowering to promote dense vegetation. Planted around ponds and bogs. Bird friendly due to dense foliage.
  • Rhagodia candolleana

Insect Pollinator Garden - Proposed Northern lake plantings - West side

The plants chosen for the west side were chosen to promote insects and other small insect pollinators. For inspiration, have a look at the Wildflower Meadow - Royal Botanical Gardens Sydney featured on ABC Gardening Australia in 2021.

  • Chocolate Lily - Arthropodium strictum - Height 60cm. 50 plants - Purple flowers in spring with a chocolate scent. Prefers moist, well-drained soils. Plants die back after flowering. A tuber in the ground will reshoot in autumn.
  • Brachyscome paludicola
  • Cut-Leaf Daisy - Brachyscome multifida - Height 20cm. 50 plants - Lilac daisy flowers with yellow centres. Flowers appear through the year. Butterfly friendly.
  • Clustered Everlasting - Chrysocephalum semipapposum - Height 30cm-1m. 50 plants - Yellow flowers. Prune after flowering to promote more stem growth. Butterfly friendly.
  • Button Everlasting - Coronidium scorpoides - Height 30cm. 50 plants - Bright yellow flowerheads in spring and summer. Insect friendly.
  • Spreading Flax-Lily - Dianella admixta - Height 40cm-1m. 50 plants - Blue flowers followed with blue berries.
  • Matted Flax-Lily - Dianella amoena - Height 20-30cm. 300 plants - Blue flowers in spring and summer, followed by blue berries.
  • Scaly Buttons - Leptorychos squamatus - Height 15cm. 50 plants - Yellow, button-like flowers in late spring and summer.
  • Showy Podolepis - Podolepis jaceoides - Height 30-60cm. 50 plants - Large, bright yellow daisy flowerheads. Flowers in spring and early summer.
  • Chamomile Sunray - Rhodanthe anthemoides - Height 30cm. 50 plants - White daisy flowers with yellow centres appearing in spring. Butterfly friendly.
  • Grass Triggerplant - Stylidium graminifolium - Height 30-60cm. 50 plants - Small tussock. White or pink flowers in spring.
  • New-Holland Daisy - Vittadinia cuneata - Height 30cm. 150 plants - Lilac-purple daisy flowers with yellow centres. Flowers in spring.
  • Wahlenbergia capillaris - 50 plants
  • Wahlenbergia gracilis - 50 plants
  • Tall BLuebell - Wahlenbergia stricta - Height 40-50cm. 50 plants - Blue, bell-shaped flowers in spring. Butterfly friendly.
  • Sticky Everlasting - Xerochysum viscosum - Height 60cm. 50 plants - Yellow flowers appearing in spring and summer. Butterfly friendly.
  • Poa morrisii - 50 plants
  • Grey Tussock-Grass - Poa sieberiana - Height 40cm. 50 plants - Small tussock. Butterfly friendly.
  • Striped Wallaby-Grass - Rytidospermum racemosum - Height 20cm. 50 plants - Grass with fine foliage.
  • Bristly Wallaby-Grass - Rytidospermum setaceum - Height 30-40cm. 50 plants - Common in grasslands. Butterfly friendly.

Insect attracting native plants - Bug Blitz

  • Any Eucalypt that provides loose bark for insects to hide under.
    • Manna Gum (Eucalyptus viminalis)
    • Forest Red Gum (Eucalyptus tereticornis)
    • Woollybutt (Eucalyptus longifolia)
  • Flowering daisies - daisies flower at different times, providing food for pollinators year-round.
  • Blackwood (Acacia melanoxylon)
  • Cootamundra wattles (Acacia baileyana)
  • Salvia - Salvias (also known as sages) flower for a long time; grow well in hot, dry conditions; and they provide a variety of bloom shapes, colour, and fragrance
  • Sweet Bursaria (Bursaria spinosa)
  • Black wattle (Acacia mearnsii) - plant away from paths and keep plant well trimmed.
  • Violet Westringia (Westringia glabra) – attracts native bees, butterflies and pollinators.
  • Kangaroo Grass (Themeda triandra) - attracts Meadow argus butterflies.
  • Purplish Wallaby-Grass (Rytidosperma tenuius) - attracts finches and other seed-eating birds like Rosellas and some parrots.
  • Common Wallaby-Grass (Rytidosperma caespitosum) - attract finches and other seed-eating birds like rosellas and some smaller parrots.
  • Weeping Grass (Microlaena stipoides) - provides food for the larvae of many different kinds of butterflies. It will also feed small seed-eating birds such as the Turquoise Parrot.
  • Tussock Grass (Poa labillardieri) - provides food for butterflies and seed-eating birds, as well as the occasional kangaroo or wallaby.
  • Kangaroo Grass (Themeda triandra) - provides food and a place to lay eggs for many butterflies. It also feeds seed-eating birds, such as finches and parrots, including the Ground Parrot.

Meadow argus butterfly in Bundoora

Filamenous algae

  • Filamentous algae forms a troublesome surface film on the southern lake at Botanica Park.
  • Filamentous algae is difficult to treat.
  • In the short term the algae will be removed by scraping it off the surface using rakes and boats.
  • Increasing the amount of vegetation in both the northern and southern lakes will reduce nutrient loads in the lake and also reduce algae growth.
  • Additional shade using trees and the installation of a floating wetland will also reduce algal growth.
  • Aquaritin can be added to control algal growth (supplier Greendrop Solutions). Aquaritin promotes the preferential growth of fresh water diatoms so that they use nutrients in the water rather than the algae. Aquaritin is currently being trialled at Peter Hopper lake, Mill Park to control Blue-Green algae (cyanobacteria).

Photo showing the buildup of filamentous algae in Botanica Park lake southern pond before removal 13 Jan 2022.

Photo showing the buildup of filamentous algae in Botanica Park lake southern pond after removal 13 Jan 2022. Note that the eel grass is still present. Eel grass provided habitat for food for aquatic animals including Black Swans (Cygnus atratus)

Lake investigations

Revegetation works

After the outbreak of Avian botulism at the lake and the duck population was reduced, a revegetation program was started. The aim was to increase the amount of vegetation in the northern lake to help reduce nutrients in the lake water and to provide more habitat for animals. The revegetation works will include the planting of both aquatic and terrestrial vegetation.

Revegetation of Botanica Park lake with aquatic plants. Northern lake - 13 March 2020.

Some new vegetation protected by netting because ducks will eat the young seedlings. Other aquatic plants do not require netting - 13 March 2020

Facilities and Assets

Facilities and assets related to Water Sensitive Urban Design (WSUD).

Construction Plans

Gross Pollutant Trap (GPT)

  • A Gross Pollutant Trap (GPT) prevents litter and rubbish in stormwater from entering a waterbody.
  • GPTs are generally cleaned every 6 months using Council trucks.
  • Council drainage trucks have a special vaccum that sucks out debris collected in a special well within the GPT.

  • When stormwater enters the GPT floating debris hits a weir (triangular structure shown in photo).
  • The floating weir directs the debris to the right where it collects in a well.
  • The well is vaccumed up by Council every 6 months.

  • The GPT well mostly collects leaf litter.
  • The GPT well smells strongly of hydrocarbons (petrol and diesel). These pollutants are washed into waterbodies when it rains.
  • Heavy metals from car tyres and car brakes are also washed into our waterbodies.
  • Most of these pollutants attach themselves to organic matter (such as leaves and dirt), so its important to trap all these materials before they enter our waterbodies.
  • You can help by leaving the car at home and riding a bike or taking public transport, and helping to pick up litter if you see it on the street.

Aeration Fountain

  • An aeration fountain (1/2 hp, 240V) was installed in the southern lake of Botanica Park by Aquatic Technologies on 17 May 2021
  • The fountain is powered using a time circuit and connected to the electrical circuit within the park (connected to park street lights).
  • Aeration can help to reduce algal blooms by encouraging the growth of beneficial aerobic bacteria. These bacteria consume excess nutrients that is otherwise available to algae.
  • Aeration helps to prevent a build-up of “muck” at the bottom of the water body. This “muck” can house noxious gases that can lead to foul odours and muddy water.
  • By aerating your water body you will reduce algal growth, increase oxygen availability for healthier fish and other aquatic organisms, reduce foul odours, improve water clarity and reduce muck accumulation.

Maintenance documents

Aeration fountain installed in Botanica Park lake southern lake to improve water quality by mixing and oxygenating the water between rain events.

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