Dam maintenance and de-silting
Dams should be regularly inspected and any dam maintenance issues addressed to avoid extensive repair work in the future.
Check for the following dam maintenance issues and address them early 1 :
- Is the dam wall leaking? Inspect the dam wall toe (where the wall meets the ground outside the dam) for signs of leakage. Patches of green grass that remain even when the rest of the paddock has dried off can indicate seepage through or under dam walls.
- Are there cracks along the dam wall? This can indicate slumping of the wall, and should be assessed by a professional.
- Has the depth of the dam been reduced due to a build-up of silt? If so, the dam will now be holding less water.
- Has stock access to the dam caused tracking and erosion on the banks or the dam wall?
- Has the dam wall eroded? The wall may need to be built up or widened, or the dam batters re-built to obtain the correct slope.
- Has the freeboard been reduced? There should be a minimum of 1m vertical height between the full water level of the dam and the top of the dam wall.
- Are rabbits burrowing in the wall or banks? This will undermine the dam’s integrity, so it is important to manage rabbits, dig out burrows and re-pack with clay-based material.
- Has the dam sill eroded, meaning that the dam is losing water before it is full?
- Is the spillway well-vegetated with grass? Is it clear of debris or other material that could impede the flow of water?
Drought can be a good time to undertake maintenance, if water levels have fallen significantly and the dam is not in use.
Things to consider when de-silting a dam:
- Move the silt from the base of the dam to the back of the dam, and use it to create shallow shelves for aquatic plants to establish on.
- Once the silt has been removed and clay is reached, use some of this clay to re-seal the inside of the dam wall if required.
- If the dam is not already fenced, consider fencing it to minimize inflow of silt in future.
A dam that is fenced and well-vegetated is likely to require less maintenance, for two reasons: the vegetation zone around the dam will help filter inflow and reduce siltation, and stock exclusion will prevent wear and tear on the banks and dam wall.
1 The material in this section is based on Agriculture Victoria’s ‘Maintaining your farm dam’ ( https://agriculture.vic.gov.au/farm-management/water/managing-dams/maintaining-your-farm-dam ) and South East Local Land Service’s ‘Farm Water Series’ videos ( https://www.lls.nsw.gov.au/regions/south-east/key-projects/farm-water )
Last update: February 28, 2023
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