Hydrometric level

It expresses the difference between the altitude of a particular altimetric reference (hydrometric zero and/or average sea level) and the share of the free surface of water in a water body (natural and/or artificial) or in an artifact at a particular point and at a given moment. You can then refer to watercourses, springs, canals, lakes, non-pressure vessels, etc. The measurement can be made directly, for example by reading graduated rods, or by means of appropriate instrumentation (hydrometers) of different types and technology. The indicator is sometimes expressed as an annual average or monthly average or daily average of a series of values measured at different time steps (e.g. 15‘, 30’,..) over a long period. Much more often is used to describe the extreme values recorded (maximum level, minimum level) and/or technically compatible with a given work.