wanting "niagara falls" is not gonna happen with 8000 gph. that is a sissy homeowner flow. our minimum we use on most backyard waterfall apps is 14,000 gph centrigugal pump. when people want a lot of water, especially on a fall that is 5' wide, you will want to step up to a 220v, but check the calculations online. there are many sites that will tell you how much gph you will need on a 5' wide fall and how many inches in height the water will be. i have the chart, but its in one of my trucks and i am too lazy to go look. good luck, rent a big decent size excavator and make sure you get one with a thumb.