A method of controlling a water reservoir supply pump arrangement determines a set value p, q, v, n of the pump arrangement based on an offset value pref, qref, nref, vref, G0 reduced by a component which is a function of a difference between an actual water level h and a predetermined water level href in a water reservoir. The difference is weighted by a proportional gain factor G. Further, a water reservoir supply pump arrangement is provided including at least one water pump and a control device for controlling the at least one pump.