A computer implemented method for predicting well or borehole performance in order to schedule maintenance activities, where the method comprises: - receiving data comprising a pumped flow rate Q from a well or borehole, the well or borehole comprising at least - a pump and - a water level sensor, - a flow meter, - said pump, water level sensor and flow meter being in connection to computer means, - generating one value of specific capacity Q/s, at a pump event, s being a drawdown equal to a static water level SWL minus a pumping water level PWL, the pump event being a pump stop/start event, comprising the steps of: - receiving a SWL value after a time X from the pump being stopped, - starting the pump after receiving said SWL value, - receiving a Pumping Water Level, PWL Y hours pumping after the pump started, characterized in that the method comprises: - selecting one or more specific capacity Q/s values which are comparable under a first rule; the first rule comprising values of static water level SWL which remain substantially invariable or equal, substantially invariable or equal comprising having a difference among values of SWL no greater than +10% or -10% from a value of reference, - iterating steps during a pump operating period so that generated values are stored, - predicting well performance by: - applying an extrapolation calculation from a group of stored selected values of specific capacity Q/s calculated before a time instant, - applying a second rule, said second rule comprising a threshold, to the extrapolation calculation in order to predict a period, after which the predicted values Q/s overpass said threshold and performing maintenance works before said period from said time instant elapses. - receiving data comprising a pumped flow rate Q from a well or borehole, the well or borehole comprising at least - a pump and - a water level sensor, - a flow meter, - said pump, water level sensor and flow meter being in connection to computer means, - a pump and - a water level sensor, - a flow meter, - said pump, water level sensor and flow meter being in connection to computer means, - generating one value of specific capacity Q/s, at a pump event, s being a drawdown equal to a static water level SWL minus a pumping water level PWL, the pump event being a pump stop/start event, comprising the steps of: - receiving a SWL value after a time X from the pump being stopped, - starting the pump after receiving said SWL value, - receiving a Pumping Water Level, PWL Y hours pumping after the pump started, - receiving a SWL value after a time X from the pump being stopped, - starting the pump after receiving said SWL value, - receiving a Pumping Water Level, PWL Y hours pumping after the pump started, - selecting one or more specific capacity Q/s values which are comparable under a first rule; the first rule comprising values of static water level SWL which remain substantially invariable or equal, substantially invariable or equal comprising having a difference among values of SWL no greater than +10% or -10% from a value of reference, - iterating steps during a pump operating period so that generated values are stored, - predicting well performance by: - applying an extrapolation calculation from a group of stored selected values of specific capacity Q/s calculated before a time instant, - applying a second rule, said second rule comprising a threshold, to the extrapolation calculation in order to predict a period, after which the predicted values Q/s overpass said threshold and performing maintenance works before said period from said time instant elapses. - applying an extrapolation calculation from a group of stored selected values of specific capacity Q/s calculated before a time instant, - applying a second rule, said second rule comprising a threshold, to the extrapolation calculation in order to predict a period, after which the predicted values Q/s overpass said threshold and performing maintenance works before said period from said time instant elapses.