i can help you . it intails a bit of work thow . you need to dig out a big part of your rockery and then get an oversized piece of realy good pond liner . i would havea pool of some sort at the top with plants in probably a liner to that overlaps your waterfall bye a good foot and sylicone it in . this makes a great filter for your pond also especialy if you can get somewatercress in there somewear . have another pond at the bottem with the pump in it . run the electric cable threw some bigger pipe that you bury under the waterfall with your water pipe from your pondso you can changethe pump if it goes wrong .realy the waterfall can go strate down or loop round like a road down a steep mountain . i would mess about with a bit of paper to see what you like . you could have a strate drop or have some eddies in the waterfall for some choice planting maybe . id get some old carpet man made to go under your liner everywear . the choice on what waterfall you have is down to you . you can buy premoulded liners even that look quit effective these days . i wouldnt but thats my choice . id buy some more choice big rocks depending on what you already have . put the liner down first after the carpet and the 2 ponds which can be any size realy then cement in stones and cobbles that arnt to sharp to your liking . it mite be worth having a dummy run before the cement ie put stones wear you think you like them and run the hose down down it and adjust if needed . when your happy get some loose cobble stones etc and spread them right over the liner and onto the soil . you could even leave some high points down the cascade to do other planting . make sure the liner is well over size of your actual waterfall so you dont loosewater when its windy or wear it splashes.i guess youl have to dig out the basic shape which is down to you .preperation is everything . anything ive missed or any other help just ask away . ps pond pumps are shown to pump x amount of water per gallon/litre . this is tested with the pump at water level . the higher the water has to get pumped the less the pump will actualy pump than what it sais .