Seaweed,

The only way I've done it is by manually calculating the flows and pressures depending on the length and height of the wall, showing a lateral leading to the wall, and putting a pipe cap symbol on the plans indicating the minimum flow and pressure at that location. It's a bit of a pain in the neck but that's how I've done it before. Then, I would just put a note on the plans to refer to irrigation detail "xx" for the installation of the irrigation on the wall. Hope this helps.