[permaculture] drainage

John D'hondt dhondt at eircom.net
Thu Jan 5 15:46:41 EST 2012


Hi Ute,

I know we have been in contact before but I can't remember on what list that 
was exactly.
You are right, I am all in favour of using trees for drainage. However 
sometimes willows can have the oposite effect of what you desire. We have a 
deep root cellar here, perfectly dry as long as the drain pipe we put in the 
bottom of it keeps clear and every year we have to remove willow roots from 
that pipe. Some 2 inch in diameter and grown since the year before. Don't 
take the roots away and that cellar fills with water to the top. So I am a 
bit doubtful about hydraulic conductivity of willow roots :(

A special problem for us is that we have a fairly decent mountain (for 
Ireland) above us and a lot of the rain falling on that mountain is going to 
come our way. A problem agravated by State Forestry who are extremely bad 
neighbours. Before planting trees they bring a 20 ton excavator in making 
ridges and gullies that end at the fence line. Where the land is steep water 
from those gullies does not stop at the fence but rather proceeds at some 
speed.
Planting willows on our side of the fence definitely slows that down a bit.

But something else that might be worth mentioning is that underground water 
veins break to the surface in many unwanted places when it gets very wet. 
There are sometimes fountains (a few inches high) coming straight through 
the tarmac of the road when it gets very wet and that of course also happens 
in the middle of fields. It is impossible to stop water that comes from a 
few hundred meters higher up, there is fair pressure behind it and if you 
try you might create a bigger swamp.

We have most of the trees you mention including Salix sachalinensis. Worth 
mentioning is Alnus rubra, the seedlings of which will take when plunked in 
a heap of loose boulders without any soil as long as it remains moist. Grows 
fast and strong.

In West Cork this seems to be our wettest year in 25 years. Is that the same 
for you?
john

> I'm in Ireland, like John, and have problems with drainage, given the high
> amounts of rainfall. I have planted a lot of willow and many other tree 
> species,
> for all sorts of reasons, including wind shelter, fodder, firewood, bee 
> food
> etc. and also drainage.
>
> It is important to remember that trees not only evapotranspirate (and they 
> do a
> little of that also during dormancy as they keep up their life functions) 
> but
> their deep roots also change the soils' basic physical and hydraulic 
> properties:
> they reduce soil water retention, increase hydraulic conductivity, and 
> loosen
> the soil structure, in comparison to grassland cover.
>
> I think what Steve may have meant when he said to keep them at a constant 
> growth
> stage by coppicing is to keep them at their maximum annual growth rate. A 
> tree's
> growth rate is higher when they are younger and levels off as they mature.
> However, for the purpose of maximum evapotranspiration it may be more 
> beneficial
> to have a large tree with a lot of leaf surface rather than a small and 
> fast
> growing one? I don't know.
>
> re willow species: I have planted dozens of different willow
> species/hybrids/cultivars on our land and I have found that here, in the 
> West of
> Ireland, the one which puts out leaves the earliest (c. late January) and 
> holds
> on to them for the longest time (into November/December) is Salix 
> sachalinensis
> 'Sekka' (Japanese Dragon willow). It also grows very quickly and produces 
> large
> amounts of biomass. Due to the very long growing period it should be a 
> prime
> candidate for drawing water. Unfortunately it does not strike easily from
> cuttings like most other Salix sp.. It has to strike roots in water and 
> then
> needs to be planted out (rather than just cutting a branch and sticking it 
> into
> the ground). Let me know if you want cuttings John or anyone else in 
> Ireland.
> I'd be happy to cut and post some cuttings for the cost of postage.
>
> Eight years ago I planted a 200 m hedge along a drain on a field on fen 
> peat
> soil. The drain borders my neighbour's land, sloping down from a drumlin. 
> Our
> field is on level ground. As the drain is no longer accessible by 
> machinery from
> either side I decided to go for 'pumping' species rather than having to 
> manually
> clear the drain. The trees also shade out the
> drain, preventing grass growth from clogging it up. Did a bit of research 
> and
> came up with the following list for our situation (also wanted something I 
> could
> lopp for our goats). All these are suited for wet sites and are considered
> 'pumping' species:
> Alnus glutinosa (Common alder)
> Alnus incana  (Grey alder)
> Betula pubescens
> Fraxinus excelsior (Ash)
> Prunus padus  (Bird cherry)
> Rhamnus frangula  (alder buckthorn)
> Salix sp. (willows)
> Sambucus nigra (Black elderberry)
> Sorbaria sorbifolia (False Spiraea)
> Viburnum opulus  (Guelder Rose)
> I planted a mix of these and they are doing well. Between taking up a lot 
> of
> water during the growing season, improving drainage, and keeping the 
> existing
> drain clear the field has definitely improved (also aided by a three-row 
> mixed
> tree & shrub hedge on the other side of the field). It used to have water 
> lying
> right at the surface for long periods. Now that's a transient phenomenon 
> for
> brief periods after heavy winter rains only.
> Sorbaria is quite slow-growing here but it finally seems to kick in now 
> (7-8
> years on). Alnus glutinosa is fantastic, very fast growing. It can also be
> coppiced for firewood. Sambucus is great of course for its berries. One of 
> my
> favourite willows for this situation is one I got from 
> westwaleswillows.co.uk
> (great supplier and great info on their webpage by the way): Salix 
> nigricans. It
> creates nice dense bushy growth, great habitat. I also threw some 
> Elaeagnus into
> the mix as I found they do well on that type of ground.
>
>
> Other 'pumping' species for wet ground that I came across but did
> not plant include:
> Acer pseudoplatanus
> Aeculus hippocastanum
> Betula nigra
> Populus alba 'Nivea'
> Populus canadensis 'Robusta'
> Populus canescens
> Populus nigra 'Italica'
> Ulmus carpinifolia 'Wredei'
> Ulmus hollandica 'Lobel'
> Ulmus leavis
>
> Of course there will be more/others for other climates and other 
> continents.
> This is a list for NW-Europe.
>
> Hope this helps all those who don't struggle to keep water *on* their land 
> but
> rather to get rid of it ;-)
>
> Ute
>
>
>
>
>
> Wednesday, January 4, 2012, 7:07:52 PM, you wrote:
>
>
> JDh> Only that willows don't do leaves here in winter when you would need 
> them
> JDh> most. They do help while growing.
> JDh> john
>
>>>
>>>
>>>
>>>
>>> G'day, I wonder how big an effect willows will have on lowering the 
>>> water
>>> table and whether your land supports many trees that can evapotransirate
>>> water out of the ground. Keeping these water loving trees in a constant
>>> growth cycle by coppicing may help with drainage over the growing period
>>> and the leaf drop will add to SOM.
>>> _______________________________________________
>
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