How much work must be done to raise 50 Kg of water through a height of 30 m?
You can say:
Work done (W) = potential energy gained (mgh),
Or you can say that
Work done is the weight force (mg) * the distance moved against the force (h)
Either way,
W = m * g * h
where m is the mass; g is the acceleration due to gravity {9.8 m/s²}; h is the height
W = 50 * 9.8 * 30 = 14700 J
If you need to do that amount of work in one second, that's a rate of working of 14700 J/s
A joule/second is a watt.
Minimum power required = 14700 W = 14.7 kW