This waterfall is approximately 20' tall. We use bags of grey mortar mix. We add a charcoal color dye to the mix. We try to build our rock waterfalls with very little to no mortar visible. Many of the boulders are placed in a way that they are locked in together

Wow, without any scale to compare, I thought the "fence" behind was approx 6 feet tall. It's great and thanks for the info. I was curious if the mortar was fortified or any sealers are used. I'm looking to build one approximately 5-7 feet tall by 15-20' wide and have recently poured a concrete basin and foundation for it. I'm going to incorporate a natural gas fire near the top and live plants near the base.