G.Dub, Pumping water to a water fall will NOT increase the flow rate of the pump. And you need to be carful expecting the advertised rated flow of any pump if the actual flow is important to you. Many submersible pumps are centrifugal types and will lose flow the higher up you pump it from the water line. A pump curve from the manufacturer will tell you what to expect compared to head pressure (pumped height above water level).

Fish on!,
Noel