Water Leakage During Pipe Transport

Does anyone have quantitative data in their area for the leakage of treated water as an average over a specified distance?  

Smart meters help and cut down the time needed to locate the leak. As many countries are upgrading their technology, the differences in the leakage are expected in different regions.
However, it seems impossible to find the mean value percentage of the water loss by transportation due to leakage.

I know that longer distance needs higher pipe pressure which creates more leakage.  
I am trying to figure out how far away from coastlines and inland salt water bodies desalination technology can be used and still be economical.

Any research or data about this is appreciated.