To view the previous 12 months issues please use the links above or
use the Backcopies link to view ALL previous issues

The GREEN HORSE - sustainable horsekeeping

Vol 27-5

In the February/March 2006 issue of The Green Horse you will find the following articles:

Talking Point and Information Exchange
Dung Beetles by Sharon Roberts
Water Divining by Fiona Adams
Weed Watch - Serrated Tussock by Nicola Field
Using A Tractor Safely by Liz Tollarzo
Grazing Management Systems by Jane Myers
Basic Fencing by Pam Brookman
Growing Your Own Equine Herbs by Fiona Adams
The Dam - A Property Asset by Chris Ferreira and Tracey Bell

THE DAM
by Chris Ferreira and Tracey Bell

Many farms and smaller properties around Australia are blessed with dams, which can be valuable reserves of fresh water over the long and inevitably dry season. In many cases however, these dams fail to add beauty and value to the property. With careful design and planning this can be overcome and property dams can become beautiful, functional and highly productive assets on the farm.

Dams – a bare hole in the ground?
Most dams in this country are built expressly to hold water and are kept bare of all vegetation as it is believed that plants will only soak up water or worse still, break holes in the dam structure thus releasing the water within. The truth is that a carefully designed and revegetated dam will not only have more water but will be cleaner, more attractive and a lot more diverse and interesting than the bare ‘hole in the ground’. Below are some of the key considerations in transforming a boring dam into a special and more productive feature on your farm.

Greening your water source
If your dam is working well, has no leaks through the long dry and you are happy with its shape, size and location, it can be a very effective move to revegetate this feature with carefully chosen trees, shrubs and most importantly, rushes and sedges (these have commonly been referred to as ‘reeds’ in previous articles).

There are some very important principles to consider when thinking of revegetating your dam:
1. Use trees carefully - as a general rule, trees (anything over four to five metres in height) should NOT be planted on the major dam walls that have been designed to hold back the water. It is true that roots in this area can break up the clay wall and let water through. That said however, trees have a vital role to play screening the dam from the hot dry winds that, if blowing across the water, greatly increase evaporation and subsequent water loss. Trees can also provide shade especially to the north, helping to keep the water cool, reducing water evaporation and stifling algal blooms. Generally, trees should be at least five to ten metres back from the walls and sides of the dams. In time they will grow to provide shade but at this distance their roots shouldn’t become unwelcome guests by damaging the dam’s clay wall.
2. Use shrubs - they can be sited in front of the trees and closer to the water; many are very colourful and will attract wildlife.
3. Close to the water use rushes and sedges – these really are the unsung heroes of waterways throughout Australia. They help to clean the water by taking and locking up the nutrients in the water, preventing the outbreak of potentially deadly algal blooms. They also help to stop erosion of the banks which, if left unchecked, can make the water cloudy. They provide an excellent habitat for fish, frogs and waterbirds, and look beautiful too. If carefully planned and sited, a mix of trees as a backdrop leading towards the banks with colourful shrubs and then rushes and sedges in and around the waters’ edge creates both a very effective windbreak and beautiful framing for your waterbody. A well designed wind break can reduce water loss through evaporation by up to 25 percent, leaving you with more water for your property needs.

Planning for a revamp
It will be essential to design your planting to get the best effect. Use an aerial photo or overhead sketch to site the plants. Remember to plan these plantings across the path of the worst hot dry winds and to leave areas open when you wish to preserve views onto the waterbody from the homestead or other similar vantage point. Weed control will be essential if there is plenty of competition, though sometimes the biggest obstacle to successful planting on dams is the hard and dry nature of the clay banks themselves. In this case you may need to drill planting holes with an auger or post-hole digger, remembering to ‘chip’ the sides of the hole if they are smooth to aid lateral root growth and perhaps even throw two shovelfuls of compost and a shovelful of gypsum into the planting hole if it is really clayey. Closer to the waters’ edge where it is squelchy, planting should be much easier. Check with your local landcare centre, Department of Agriculture and or Shire environment officer for details on suitable species.

What if the dam leaks?
In many cases dams on slopes leak, which can be a major disappointment or even the difference between life and death for stock. This leakage is usually because the dams have not been formed out of good impervious material and have too much rock and or sand in the mix.
There are two broad strategies for remediation and both are usually pretty expensive.
Most people look to seal the dam with expanding clays – usually this involves using Bentonite clay at high rates. This fine, white, expanding clay is applied to the dam and thoroughly incorporated into the dam surfaces. When it becomes wet it will swell up pushing closed the gaps in the dam and thus helping to create a good seal. You will probably need heavy machinery such as a dozer to undertake this work.
The other option is an artificial liner made from geo-textiles. These are very tough but need to be expertly laid in clean soil without rocks or sticks which can eventually puncture the liner.
In the height of summer you can lose up to 10 millimetres of water per day through evaporation, so don’t discount the value of dam covers which are increasingly being used and can save the property enormous amounts of lost water.
Your local Department of Agriculture or rural stockist should have some idea of local contractors who can do this work , and there are also many dam consultants and contractors in horticultural regions where farmers use a lot of water and rely on good dams for production.
Once the dam is holding water you can then set about careful revegetation to compliment and build on this important repair work.

Water Harvesting
In many cases dams can also be improved by increasing their size and the water catchment that feeds them. This is called water harvesting and usually involves making earth banks to capture, collect and then direct water into the dam that would otherwise just run off down the slope and away from the dam. There are many farmers who set up such banks across the slopes above dams to intercept and then use this precious runoff. Banks need to be sited very carefully to ensure that they are at just the right angle to collect the water so that it does not run into the dam too quickly or not move at all, staying in the banks to evaporate away. Generally when designing such banks, the chosen sites are pegged by a surveyor and then constructed by a road grader. If they are well designed and working properly they can significantly increase the amount of water captured for your dam. They can also be planted with trees and shrubs to add even more value to the landscape.
In all cases your dam should have a well designed overflow to cater for flash flooding so that excess water can be safely directed into adjacent water courses or even other dams lower down the slope.
Dams can be so much more than bare holes in the ground and if well vegetated and managed they can be significantly improved to provide much needed water, visual relief and value on the farmscape.