Pool pumps are usually centrifugal pumps. Centrifugal pumps usually operate in a pretty narrow pressure / flow range, where a slight change in the resistance of the piping will show up as more amps drawn ... though there may not be much change in the discharge pressure.
I'd suggest looking to be sure all the right valves are open; then checing to see if the filter media is in need of replacement / back flushing.
Rod's suggestion - check the bearings and alignment - is also a good idea.
Finally, you said this was a three phase motor. When was the last time your meter was calibrated? Is it s 'true RMS' type meter? Has the increased amp draw been a new development - or has it always been that way? Is the draw the same on all three legs?
