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Ducks, photo by Richard Nunn

A Dam Good Idea

By Jonathon Howard

I’ve built a series of ‘leaky weirs’ on my property. A leaky weir is a structure designed to slow water flow, filter the water through the vegetation, and reconnect the water to the surrounding floodplain.

People might be familiar with these structures if they have seen Peter Andrew’s ‘Natural Sequence Farming’ on television. If you haven’t seen them, they are basically a series of erosion control structures made from rock, earth, and vegetation that slows water as it flows over the land.

Ideally leaky weirs create wetlands and habitats along a creek. When built at scale, they also improve water quality and create more sustained water flow during dry times.

My weirs lie along a normally dry drainage line that leads down to my main dam. My weirs are small scale, but even small-scale efforts can help moderate water flow, reduce soil erosion, and create wildlife habitat.

How do I know this? While other neighbouring properties have dams smothered with azolla (duck weed), my dam has remained healthy. I believe the difference is that the weirs above my dam capture the nutrients before they reach the dam.

There are now a family of wood ducks with a brood of about a dozen babies living around the dam. Other species of duck, cormorants and grebes also visit. I have water reeds rather than a mass of floating ferns.

It is not just the dam that has benefited. The creek line where these weirs have been built now has a number of wattle and eucalypt seedlings emerging- reflecting the increased availability of water in the surrounding soil.

My weirs don’t trap the water they just slow down the flow. When it rains they create a series of shallow pools for a few days. The water then ‘leaks’ away. I now have frogs, lizards and many other small creatures sheltering along the creek line.

ANU’s sustainable farming initiative (see; https://www.sustainablefarms.org.au/) has found that there can be wider benefits. That is because improved water quality can lead to increased weight gain in livestock. My attempt is simply on a hobby farm.

Imagine if our creeks were rehabilitated in this way… If we created a ‘chain of ponds’ that buffered our landscape during times of floods and drought. It would be a win-win for both farmers and wildlife.

Ducks, photo by Richard Nunn