Not sure where to post, so trying it here but also posted in the irrigation forum too.

There are large boulders behind my house, it slopes up to about 40ft or so. Some of them are over 10ft tall. I thought it would be so cool to plant some bougainvilleas in between the boulders so like a hill of color.

If the objective is to store a 50 gallon of water on the top of the slope then use gravity to drive low pressure drip irrigation to water the bougainvilleas. What would be the most economical way to deliver water to the 50g storage? I think 50g is enough for a week of consumption so we don't need speed.