Australia may be the second driest continent on Earth, but it is still pimpled with various marshes, swamps, bogs and wetlands. I have tried to recreate our native swamps as a centrepiece to my parent's garden. This page explains the current status, the original design and implementation has been kept for posterity.
My parent's house is on a very steep slope, about 2:1 average, and it is sitting on the outside ridge of the hill. To provide suspension of disbelief we need to provide a reasonable story to explain why there are two large ponds in such a location.
The lower pond is reasonable as it is surrounded by houses and built up areas everywhere but the low side, which we have hidden with a fence and some climbers. The upper pond has no such cues. The idea is that like many places around Melbourne, such as the Christmas hills and Churchhill National Park, we have a small piece of old aquaduct winding around the edge of the hill. To present this we have a path running along the down side embankment.
I made a map showing the spot heights and estimated contours of the area under consideration. One thing that helped was the previous construction of a terrace for a trampoline. David and I then moved a lot of dirt to build the ground up and down. The original path had to be realigned, and a bridge was constructed to cross the new creek path.
It is important to ensure the slopes are all correct for a good stream, otherwise water piles up in the gentle parts and leaks out everywhere. Too steep and the creek bed erodes, requiring expensive, and ugly, concrete work. We effectively reduced the slope required by putting a rock shelf waterfall in next to the bench seat.
The first thing I've noticed with making realistic water features in a garden is that you need to be serious about the earthwork. To build our current design required moving about 4 tonnes of wet clay and carefully placing another tonne of granitic sand, pebbles, plain sand and large rocks. And it still doesn't feel right in a few places.
Once the earthmoving had been finished we were lucky enough to have a huge downpour that filled the top pond basin with water. We puddled the clay pan underneath, allowing, at least in theory, us to avoid the use of a liner. However, as water is so unreliable, and due to the proximity of a large number of very thirsty gum trees, a liner was essential.
We covered the black polybutylene plastic with a layer of washed sand (from the garden supplier) and then covered that with about 10cm of granitic sand, a fairly impervious coarse sand/gravel mix made from decomposed granite. Then a fairly complex pipe system was installed to allow the pump to recirculate the water, and rain to top up the ponds.
The most exciting change (well, in my opinion - ajh thinks the pump is the bee's knees) is the development of a sphagnum bog with an alpine flora. The outside of the creek is Sphagnum with a Richea continentalis, a Brachyscome nivalis and a Gunnera cordifolia. The inside is a peat bog with Poa costiniana, Centella cordifolia, Bracteantha paludosa and a Cranberry bush (doesn't really belong).
Around the waterfall are many ferns and rock orchids, including a large Dendrobium speciosum. Along the creek are Bauera rubioides and some small grasses.
