I'm trying to irrigate a garden plot that is 70' above and 700' away from a creek at the bottom of my land. I understand that I need a pump with over 70' total head in order to raise the water from the creek to the garden, but I'm wondering how much the output (GPM) and water pressure will be affected by the change in elevation.

I've considered building risers for some 300-gallon water tanks, filling them from the pump line and then running sprinklers from hoses attached to the outlet valves of those tanks, but I need to know whether the pressure from gravity-fed hoses will be sufficient to run impact sprinklers. Would it be a better idea to connect the pump down the hill directly to the sprinklers and skip the storage step altogether? If so, what specifications should I be looking for in a pump to deliver the required pressure?

One last question: Most pumps I've found that deliver 100+ gallons of water per minute have 2" inlets and outlets, but based on my research 700' of 2" poly pipe is going to put me out two or three times the price of a pump. The same length of 1" pipe costs significantly less, but will using adapters at the pump inlet/outlet and running smaller hose adversely affect the output of the pump?

Thanks,

David