Drip irrigation has been grossly oversold.
Drip irrigation reduces surface evaporation somewhat, but does not do nearly as well as my friend's technique. It has numerous problems, not the least of which is root clogging. The emitters that drip the water tend to get clogged by thirsty roots, which prevent them from working. Also, water is still lost to capillary action to the surface followed by evaporation.
My friend taught me that the key to minimizing water use is getting the water to the PLANTS, not to the soil.
David F Mayer