Underground watering

I live in Denver. It is always dry, and now we are in the middle of another drought. More water restrictions and so on.

Watering under the ground, or at least, under the mulch, seems to make sense to me. Less water would evaporate into the hot dry air.  But is there a way to do this without it being an expensive engineering project?

I have tried using bottles with holes poked in the lid. In my experience, they either get clogged up, or empty out right away.

I have also seen expensive kits that regulate pressure and all that. For me, that kind of stuff is too big a deal.

Any ideas how to do this?