Flood Irrigation

I was remembering that when I was in New Mexico and in tuscon AR all of the pecan farms were flood irrigated and so I went to this site to see if it was necessary to do this type of irrigation and to get water uniformely in an orchard underneath the canopy of leaves and branches this is how the orchard needs to be watered. I know there are fields that dont need this type of irrigation but the farmers are too lazy to up grade.