i dont know about the SA breed but what i know about eucalyptus (aka blue gum) in general is that they drink kisawasawa.....we are talking 50 liters per tree per day! so definitely they affect water tables. for example ealry last year,there was a decree (i think by michuki) for farmers to clear this offending tree from within 20 meters of water sources and water ways (rivers etc). amazingly,streams and dams/swamps that had since been drained out by the tree,re-emerged!! those that had been reduced in volume,suddenly started surging with increased volumes. i have seen it with my own two eyes...it is like a miracle!

also land where these trees have been grown has been shown to be unable to support any other type of vegetation even after they are cut down.

the irony is that these trees give very good returns...and i am guessing this is your dilemma. hard choices,eh?