From John Skidmore
Doug Cross describes salinisation of freshwater aquifers following over-abstraction near the sea and resulting in negative hydrostatic pressure (30 April, p 28).
In the Murray-Darling river basin in south-eastern Australia, exactly the opposite has occurred. Excessive irrigation with good-quality fresh water from the Snowy Mountains on productive farmland situated over extensive salty aquifers has resulted in a disastrous raising of the saline water through positive hydrostatic pressure. First trees, then vegetable crops die, to be replaced by unproductive salt pans when groundwater breaks the soil surface.
Kangaroo Valley, New South Wales, Australia
