The top curve is for the pump I'm working with. The rain bird sprinkler I'm using has a 7/8" main nozzle coupled with a 3/8" drive nozzle and a smaller nozzle. I'm hoping the pump matches with this sprinkler to the higher volume side of the curve, between 130 and 140 GPM. The problem is the Rain Bird 100B is an antique as far as sprinklers go and I've been unable to locate accurate performance specs on it. I'm using other impact sprinkler heads with similar nozzle sizes to get in the ballpark on my estimates.