Posted: 27/07/2015 at 06:56
I have no experience of growing olives on that scale - but my initial reaction to your first picture is that the olive tree is surrounded by much bigger trees which must be taking all the water from the soil.
Have a look at successful olive groves in your area - are the olive trees surrounded by other trees or do they each have plenty of space?
Watering once a fortnight isn't very much at all - how much water do you give each tree?
I agree with BLT, talk to local olive growers - make friends and seek their advice