The piezometric record is the collecting of the evolutions in time of the monitored groundwater level or piezometric level (see piezometric level). It consists of measurements that link the water level to a given date. Depending on the variability of groundwater level, the measurements are more or less close in time. The measurements obtained are positive or negative with respect to the measurement benchmark: they are positive when the groundwater level is below the benchmark measurement (the most common cases) and negative in the opposite case (artesian wells). Artesian: a well is artesian when the water is gushing. A record is represented by a curve which is time-slotted to be stored in a succession of points, each point representing a groundwater level at any given time. Points are linked to each other by means of a code that indicates whether a point is related to the preceding point in time. If the point is not related, it is then the initial point of a new part of the record. The presence of an initial point also characterizes the lack of information on the groundwater level for the period that separates it from the previous point.