Extensive Roof Garden University Project

[GD001]

Hello everyone!

I have a university project on contructing a prototype for an extensive roof garden and I had some issues I would like to ask you about.
Mainly, the issue of irrigation.
Extensive roof gardens usually depend on natural rain water as a means of irrigation, however, I would like anyone, with experience, their opinion on extending a single perforated hose down the center of the garden to surround with the more water dependent plants. The reason I'm considering water is because summers in Lebanon are VERY HOT and VERY DRY and we have no rain fall during those months whatsoever (especially in the city).
This issue of irrigation confused me with my plant selection. I had initially planned on a variety of colorful sedum succulents but also wanted to integrate a few short ornamental grasses and some native summer wildflowers like poppies and daisies. I also was considering short plants like small-leaved Thyme and Chamomile so give the space a small "harvest-factor".

Does anyone believe the absence of irrigation will allow my more herbaceous plants to survive? Or should I install a perforated hose and position the water dependent plants around that hose? Also, the watering schedule should be daily, I'm guessing?

Thank you very much for your advice!!! =D