IrrigationLandSwalesWater ConservationWater Harvesting

Designing Swales in Central Victoria

by Samantha Downing

One of the major assets of our property in Central Victoria is a storm water culvert which brings storm water runoff from a number of roads nearby. Water begins to flow through the culvert whenever we have rainfall of more than 8mm. After 25 years of water pouring onto the property, a large gully has been washed away, and this is one of the places in which Gorse (Ulex europeaus) has found a niche.

This satellite pic shows the course the gully runs and the growth of gorse around it. The main swale bisects the water course and now directs water across the property on contour.

The first priority for setting up our permaculture system was to more effectively use the water currently running straight off the property and to slow it down to help with the erosion problem. This led to a design for the mainframe swale, running on contour at the highest point that traversed the longest line across the property. This was partly determined by looking at contour maps, to help decide where we would begin surveying. Online contour maps promised a level line that ran from one far corner to another, beautifully traversing boundary fences and sheds. However, there’s nothing like getting outside with a laser level or A-frame… as while pegging it out it began to look somewhat different. South of the gully the swale would run just where we wanted, but on the north side, it ran into the boundary fence. We opted to build the south side swale and come back to the northern paddock at a later date.

Digging the swale at the end of summer, the ground was too hard for the bucket on the little tractor. First the pegged line was ripped a number of times and the loose earth was scooped and piled on the downhill side of the swale.

Levels were checked by hand by moving along the swale with metal tubing and a spirit level. Constructing swales seems to have a magical meteorological effect — I’m not the first to be rewarded with rain the day a swale is dug. Water is the ultimate spirit level and indicated the need to dig a bit deeper at the bottom end.

The top side of the swale was planted with a variety of acacias — blackwood, black wattle, lightwood and wirilda in the mix. The last thing to do was to make a bridge to the lower paddock.

After years of drought, rainfall this autumn and winter has been constant. The swale has been full since April, resulting in waterlogging in the paddock below. When it came time to plant bare-rooted fruit trees, we decided to mound them up to prevent them drowning. As it turns out, the bottom end of the swale is somewhat higher, which means the ground below is less damp, and a good place to plant cherries, peaches and apricots, which are more susceptible to waterlogging. When things dry out again, the plan is to deepen and widen the swale. Having thought in terms of water scarcity for so many years, I didn’t account for how much water would be coming through that culvert. 80mm fell in 24 hours in August, blowing out the walls of small ponds we had constructed to slow down the remaining water that travels through the gully.

This represents a major challenge. We’re grappling with how to deal with the force of the water flowing through that small channel in big rain events. There’s also a concern about contaminants coming onto the property that have washed off the roads, particularly for the two small dams scheduled for future works. For the time being, the big rains are cleansing, washing up an assortment of rubbish and old bottles that have been thrown in that gully for countless years.

8 Comments

  1. I’m a Victorian too and i know how dry its been. The rain has really been a blessing. Great to see free water collection, but that torrent does look like its washing a lot of the fertility out of the land. At the risk of being chased by a mob and the government departments… perhaps black willows planted in a thick clump can slow the flow of the water leading out of the culvert. The willows would suck up any pollutants, trap the bottles, and be used for lumber. Great stuff you’re doing.

    Please keep us updated with photos!

  2. When reading your article it occurs to me that a larger swale will most likely do nothing to solve your water-logging problem. It may be a better idea to do some ripping with a yeomans plow or other similar device across your whole landscape. It sounds to me that you have a compacted layer below your topsoil that is not allowing any water to go into the sub-soil. If you can break the compacted layer and increase the depth of topsoil and the blend between top and sub soil I think you might find it less likely to water log in the future as you have increased the water holding capacity of more of your soil. I think a larger swale may actually make your problem worse.

  3. Thanks all for the comments, and lots of interesting suggestions. We’re located just outside of Castlemaine in Central Victoria. Adam, I recall that there is a hybrid willow that Darren Doherty mentions in the video “Selected Tree Species Tour” over at https://www.taranakifarm.com/blog/?cat=22 that has been okayed for planting.

    Evan, I agree that a larger swale may not be such a good idea. I have been changing my mind about that recently. Would like to do some ripping with a yeoman’s plow. Let me know if you know of one in my area. There is plenty of water in the subsoil. It’s our first year here, so it will be interesting to monitor it over summer to see how much water is retained in the soil and compare with the soil above the swale. The plan now is to set up a better drainage system, to be able to completely drain the swale when required. The rainfall we’ve received this year hasn’t been seen for 10 years or more, so we’ll keep observing how it functions in the winter’s to come.

  4. Seeing as how you are already aware of Taranaki Farm I would suggest you contact them about a Yeomans, they are located near Woodend which is in your general area, Darren Doherty is also located just outside of Bendigo, I think either Ben from Taranaki or Darren would be more than happy to help you find a Yeoman’s near you. Good luck

  5. just a quick note. when you build your ponds you need to place them to the side of your water flow so the water enters and leaves at the same height. this will slow the flow and prevent blow outs of your walls. I have done many of these in Victoria & NSW. feel free to contact.

  6. If you want to slow down the water, meander your swales as long and wide as you can like a drunk weaving, back and forth so that the water has to go over to one side, then down to the other, not in a straight line so that it sinks into the soil and at the same time there is less chance of flooding. I’m putting in a swale on a small property now and will do the widest meandering I can on it because when it pours, it really pours. Good luck on your project. On the island I’ve been pondering on building a waterwheel system from the lake to the house and that’s been a years-long ongoing project because when it rains, it floods; when there’s a draught, the water cedes about 200 – 400 feet from the island boundary so you can see all the potholes and lava rock. Very interesting.

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