Question about dam water

Discussion in 'Designing, building, making and powering your life' started by Spidermonkey, Mar 13, 2014.

  1. Spidermonkey

    Spidermonkey Junior Member

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    Hi Guys,

    As I mentioned in my other thread "Planning to Cross the Line", my family and I are looking at properties in the Tenterfield area of NSW. On thing I have noticed in most of the places we have seen is that the water in the dams seems to contain brown / orange colour sediment. When I did my PDC at Zaytuna farm the water in the dams where all clear which I assume that this is due to slow passive water collection. Would it also be correct that the plants in and around the dams play a part? Aquatic plants seemed to be a prominent feature in Zaytuna farm's dams.
     
  2. rmcpb

    rmcpb Junior Member

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    Many dams are just holes in the ground to collect water from drains. They tend to have dirty water as the energy of the water in the drains or across fairly bare paddocks picks up the clay and that stays suspended in the water for a LONG time. Also, many people let their stock drink directly from dams which allows them to continually stir up the water near the drinking point.

    I would imagine the water in the dams at Zaytuna is collected in swales and directed gently to the dam in a low energy way. Also, there is likely to be nearly 100% ground cover on the catchment and the dams include aquatic plants. So the water cannot pick up so much clay and the bit that does get collected is filtered out by the aquatic plants.

    Cheers
    Rob.
     
  3. Terra

    Terra Moderator

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    Plants around the edge will help a lot , the fine particles in suspension drop out , but on the edges the wind will keep mixing them in again . Catch pits (small dam before the main dam) will catch a lot of sediment from inflows these need to be designed to slow the inflow to allow sediment to drop out . On my families sheep station 60 / 70 yrs ago most of the fresh veg was grown around the edge of dam catchpits fenced off of course from the sheep and rabbits the silt is a great resource . Good idea to clean the water up before it goes into the dam saves a lot of cost later on to clean the dam out , a catch pit can be done any time its more or less dry .
     
  4. PermaGuinea

    PermaGuinea Junior Member

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    Another thing to watch for is whether the dam is close to a gazetted road. Many dams inadvertantly collect run-off from roads, including herbicides sprayed on the verges by councils and other government departments as "weed control", as well as other toxic products of road maintenance (tar, etc.) and usage (rubber dust from tyres, etc.)

    If you have non-permaculture neighbours and can't be sure what chemicals they are spraying on their side of the fence, it is prudent to have a buffer such as a sacrificial swale along your boundary to stop their runoff ending up in your dam and killing all the beneficial organisms.
     
  5. rmcpb

    rmcpb Junior Member

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    This is good advice in areas where rainfall is plentiful and regular like the north coast of NSW but in the more arid areas water is gold. We use the roads to run water off into fairly large dams that let it sit for quite a while before we have to use it so the dilution effect combined with the micro-organisms get to clean it before its used. Using this water on the more extensive areas is priceless in the dryer areas.

    After saying this, it would be better if we didn't have to use it but, that's life in some cases.

    Cheers
    Rob.
     
  6. Spidermonkey

    Spidermonkey Junior Member

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    Thanks Guys,

    This is really useful to know.
     
  7. bazman

    bazman Junior Member

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    I don't really agree with the road excluding water as it is a major part of my hard surface water catchment. This water comes in via vegetation drains, flows across a paddock into a long vegetation swale, then flows into another drain then onto my dam. Council's can be hard to deal with, with regards to spraying, but I have done the best that I can in listing as a no spray area (talk to the council contractors when you see them, as they are often ok with no spray areas, the guys doing the mowing often do the spraying). Roads and road drains are an important catchment for many Permaculture properties and should be carefully thought about and designed around. A heavy 75mm down pour can put 50cm+ of water in my 1.5meg dam, it would not be any where close to that without tapping into my local road drains With regards to water in your dam, lots of vegetation around the dam, in swales and drains will help to reduce sediment, but from time to time it will change, mine is a dark black water when full and happy, but we are in drought at present and I have been drawing heavily from it so as it drops it tends to go cloudy again. This will also depend on your soils and the type of clays used in sealing the dam.
     
  8. PermaGuinea

    PermaGuinea Junior Member

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    Yes, I agree. I am not saying exclude the road water, just that it is wise to have buffers and filters in place. Sounds like you have that. Many don't, especially non-permies. I've seen some pretty toxic-looking dams on non-permie properties.

    It is great that you have talked to your council contractors and got them to stop or reduce their spraying. Our neighbours reduced their spraying in the neighbouring paddocks once we mentioned we had a baby.

    I agree that a good permaculture design generally slows water flow down and incorporates swales and extra vegetation that help filter the water before it gets to the dam. Anyone buying a non-permie property to start a permaculture project, however, should probably bear in mind that the previous owners may not have considered water quality in the same way we would. Sometimes people add "polymers" and other stuff to try and seal leaky dams.

    Like yours, the water in our dam gets cloudy as the level drops, but the vegetation and fish (perch and cat fish) are thriving and that would indicate that the water quality isn't too bad. The water did get an oily looking film on it earlier in the dry season, but I think that was just natural oils from the exposed clay and decomposing vegetation. It cleared again after a few showers of rain.
     

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