I don't understand the operating range on a pump curve

Hi everyone. I am brand new to pump sizing. I'm currently attempting to size a pump to transfer water from one 4 ft tall 300 gallon tank to another one. The issue is that I cannot find a pump that has the appropriate operating range for a total dynamic head of less than 10 ft. I'm looking at about 5 ft of TDH and I want a flow rate of 100 gallons per minute. Should I buy a pump that will operate at this flow rate with more head? I don't really understand why any pump curve stops before reaching the x-axis. If the pump can handle 25 ft of TDH, why not 2.5 ft? Thanks in advance for your help.

The pump curve shows the most efficient operation of the pump, the reason they want some head, is to transfer load properly to the appropriate bearings. The phase power has nothing to do with the pumping.....all you'll need is probably a 3 hp, and there are plenty of options for single phase motors, either on centrifugal pumps or submersible. Don't forget about friction loss when calculating head.....100 gpm through 2"discharge piping will help alot creating head. Call a real pump sales company.....Berkely will build a pump to meet any conditions you give them, and this should be an easy project.