[permaculture] "thirsty " trees....

permed at nor.com.au permed at nor.com.au
Wed Sep 4 13:04:20 EDT 2002


>I have been surprised to read references from Australia blaming the 
>ABSENCE of trees for RAISED ground water levels, because all other 
>references accredit the PRESENCE of trees with raising the water level. 
> I can't pretend to understand the mechanics of either of these 
>assumptions, at least that's what I believe they are.

This  phenomena is associated with soil salting in inland areas of 
Australia. Previous open forest maintained the groundwater levels and 
more importantly maintained a freshwater layer in the upper ground water. 
Many of these areas were once part of a large inland sea and the lower 
groundwaters are quite saline.  The forest facilitated the infiltration 
of fresh rainwater and through transpiration kept water levels down in 
the flat areas. With the trees cleared groundwater levels under the low 
rolling hills has dropped and on the flatlands the ground water levels 
have risen bringing saline water to the surface. Difficult to explain in 
a nutshell without diagrams but hope this short explanation has helped.
Robyn



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