Is improving the irrigation efficiency really beneficial?

Hello guys,

I would like to discuss a topic that was popular during my studies and kept me thinking for a while: Is improving the water use efficiency on field-scale really beneficial for farmers?

Physical losses on field level can be found by deep percolation, runoff and evaporation. In this way these "losses" can be used by other farmers by groundwater/surface water, or it returns in the water cycle by rainfall.

So why should we be aiming for the most efficient irrigation system? How do you think about this?