Gardening with Em: dams, ponds and tips for aquatic habitats
Submitted by Holly on 26 Nov 2020.
With the summer now upon us, the hot temperatures may prove too warm to be planting land-based plants. However, this is the perfect time for planting in the water. Em Bowman from Stem Landscape Architecture and Design shares a case study of one of her latest projects:
Water habitats are life attracting and are essential to the health and vitality of most ecosystems. If you are thinking of creating a thriving ecosystem that encourages a diverse array of animals species, then you may be interested in a project we at are currently undertaking.
We have been working on a dam conversion, and although this is a lot larger than a pond, the same design principles apply to the success of the biodiversity it draws in. So in this piece, I thought it would be great to reveal our build and some handy tips on wetland and pond construction.
Our brief was to revamp an existing large dam, used mainly to deliver water to livestock. The new owners bought the 35-acre property as an opportunity to get away from the city and enjoy life in a rural setting. With the dam being perfectly positioned in front of the house we thought why not keep it as a functioning dam, but improve it by turning it into a wetland. Here we are still allowing it to operate normally as a dam, but it can also be enhanced to contribute back to the environment, provide habitat to local wildlife and in return, the plants will provide cleaner water to livestock.
By definition, a dam is a barrier that stops or restricts the flow of water or underground streams. This then becomes a reservoir that is used for a range of activities. In this case, this dam was used as a water source for livestock and irrigation.
Clay is the usual material used in agricultural settings, it lines the base and walls of the dam to make it hold water, and unlike natural water bodies formed over thousands of years, dams are constructed to slope dramatically and unnaturally inwards. In contrast, creeks and wetlands have shallow, medium and deep water bodies, varying edges, silty soil deposits and a variety of natural elements like boulders, logs and plants to help stabilise the edges and form habitat to a range of different animals. This is what we need to replicate when building a pond or revamping a dam. So first we need to reform the edges and shape of the dam/ pond to have deep, medium and shallow ends. Shallow zones are anywhere between 50mm- 300mm deep, medium zones are 300mm- 600mm and deep zones are 600mm- 3500mm. You also need to ensure that there are ledges and varying heights on the banks. This allows you to add soil to the small underwater pockets and is where you can plant aquatic plants. Because clay lines the dam, only a limited number of plants can grow in the heavy medium that is why we add a sandy loam soil so we can plant multiple other species that would not naturally grow in dams. Rocks and logs should also be added into the water, this provides habitat, platforms and protection for a wide range of wildlife.
Plants are obviously a significant source of food, protection, habitat and nesting material to a variety of bird, insect and animal species. This is why we must ensure we have pockets and undulated edges as we can allow different types of plant species. Rushes and sedges occupy shallow water and the edges of the water body. In a pond, rushes are great for certain insects, but they also provide protection to aquatic species when birds come in to hunt them. In a larger setting like our dam, rushes and sedges are the perfect place for dusky moorhens, reed warblers and other animals to nest in.
Aquatic plants that usually occupy medium depth between 300mm- 400mm are species like Myriophyllum crispatum, Triglochin procerum, Villarsia reniformis and Marsilea drummondii. These plants are a great nesting site for frogs and fish, and in turn, they are also a food source to predatory bird species like our friend Harry the White-necked Heron.
Whilst planting, we have already observed Australian Wood Ducks, a Sacred Kingfisher, White-faced Herons, White-necked Herons, ibis, spoonbills, flycatchers, Australian Magpies, Laughing Kookaburras, Galahs, Crimson Rosellas, Crested Pigeons and Welcome Swallows come to visit for a sticky beak and a drink. We also heard and uncovered Common Froglets, Pobblebonk frogs, and an Eastern Brown Tree Frog whilst planting.
We can’t wait to revisit this site in a year to see how much more wildlife is drawn in. I will be sure to update you on the changes in plant growth and what visitors have been drawn in to call our new water habitat, home.
Photo: Dam before conversion. Em Bowman
Photo: Dam after conversion. Em Bowman
