All seriousness though... what's the service here? Commercial? More than one household? That 4m³/hr translates to almost 18GPM American, and here typical is 5-12GPM for residential, with most being in the low side of that range. And we are horrible water wasters.
mnem
Got to water the Sheep - Insert Baaaaad New Zealand Sheep Shagging Joke here
Water from pond at the bottom of the hill pumped up a big hill to a storage tank so it can be gravity fed to stock troughs back down the same line in most cases.
Exactly this ^.
50M lift, 40mm single poly line that acts as pump delivery and main farm feed line.
Typical summertime max usage is ~1500 gals/day.
All cattle here.
Gotcha... so still plenty of pump to keep up with demand at ~26,000 gal/day theoretical max capacity modified by the losses from 50m head and 40mm pipe diameter. Just can't do it against a wide open 40mm line like the old one would. I used to know this math... but I'll leave that part to you pros; I grok what's important here.
mnem
*Slippery when wet*
Yeah got heaps of pump capacity and always had/wanted that. Didn't want a pump that ya had to have goin all the bloody time.....just like they say for IC engines, there's no substitute for cubes.
But ya have to give them the pipe to breathe properly.
Additional friction head was calc'ed by 250m of 40mm whereas there's only ~200m plus 50m of 50mm poly up high by the tank where it can handle the pressure.....it accounted for an additional 11m of head so we worked on 60m of head which should also allow for the frictional looses of the few fittings in the line.
Think of fittings as additional resistance in an electrical circuit.
At this time it's all manually controlled with a tiny wireless remote back at the house some 500m from the pump (see my Antenna Project log thread) however I've had designs to automate it with a PV powered tank level sense blipping the pump an ON/OFF signal to the pump house.
Done the circuit, breadboard proofed it all and routed the PCB, got the transmitter, PV, enclosure and made all the mounting metalwork and sense probes. Need to etch the PCB and slam it all together....one day.