Heya and welcome.
I need to make a quick point here:
Interrupting the flow of a natural stream without an ecological impact study, public hearings, permits, engineering plans, etc is illegal and virtually guaranteed to draw unwanted attention to your grow and yourself if anyone sees you.
Just a heads up for you safety and also honestly for the environment, because we need to remember to keep up a good ethical image among growers.
That being said, there are certainly ways to irrigate! Have you considered a rain barrel of some sort... I am imagining a 55 gallon drum sunk into the hillside up=grade of your grow, with buried irrigation drip lines fed by gravity, leading down to where your grow is. I'm not near a piece of paper but I'll draw a diagram tomorrow if someone reminds me. Then upgrade of the rain barrel, you hook up a very simple trench system to fill the barrel, and a simple filter over the intake... this interests me because the big PITA of outdoor is carrying water.
Hmmmm I have to think about this a little.