You need the following:
elevation above sea level of pump
elevation change from pump to highest sprinkler head
elevation from eye of pump to water level
size & type of suction line piping
gpm of largest zone
pipe sizes & distance to farthest head
head pressure needed at nozzle

That's a pretty good start.

--
Baine

"Eugene Ferreira" wrote in message
...
Hi

I am trying to find out how you determine what sizeof pump you need to
keep
the water pressure in an irrigation system. I stay on a farm and we're
watering from a dam, so there is no water pressure.

Eugene