I have to wonder if this result is due to increased evaporation (from the dam surface) or increased transpiration (from non-irrigated and irrigated fields). With oxygen isotope analysis the two can be distinguished.

This type of analysis reveals that trees are responsible for about 80% of all terrestrial rainfall.[1] In contrast to man-made desalination facilities, this water falls freely as rain instead of being owned and controlled.

Global deforestation/desertification is perversely convenient for those interests vying to control water, since in a very real way it eliminates the competition.

[1] http://www.nature.com/nature/journal/v496/n7445/abs/nature11...