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According to the hydro-geological meaning, a water volume supplying an aquifer over a given time. Rainfalls are mainly recharging groundwater. Unconfined groundwaters are recharged rather fast at each rainfall event. The rise in water levels and rainfall events are observed on a piezometric curve.
Elevation defined either in NGF level (French levelling network) or in relative depth. The NGF level, established under the control of the National Geographic Institute (IGN), is the reference. NGF can indeed express altitudes in one and unique reference system, i.e. as compared to the same and unique fundamental point (or "origin-zero" or point zero). The "0" level is the average sea level in Marseilles. This point is used to determine the altitude of any other point. The elevation of the piezometric record can also be expressed in relative depth with respect to the benchmark of the
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…
Value (flow rate of streams, groundwater level, reserve storage, etc) necessary for the quantitative management of the resource. The quantity goals are set to achieve a satisfactory balance between the demands of human activities and the requirements of aquatic environments on the one hand; and the surface and groundwater resources that can be mobilized, on the other. At nodal points, these values are the
Extraction of fresh water from a groundwater source or surface, permanently or temporarily, and conveyed to the place of use. Water abstractions include all activities related levies generated by agriculture, industry (including energy), the supply of drinking water, or other (mineral spring authorized, production artificial snow).
Area on which the water that soaks into the ground supplies the abstraction for drinking water.
Warning issued in advance by the departmental flood forecasting services. In the event of heavy rainfall or hydrological alert, a flood warning is sent to the Prefect, who then alerts the mayors of the catchment areas concerned.
Warning issued in advance by a special state service (flood forecasting service). In the event of a rainfall or hydrological alert (triggering when thresholds are exceeded), the flood forecasting service offers the Prefect the alert of the mayors of the watersheds concerned. As a severe overflow flood, the flood warning service broadcasts, for prefects and mayors, hydrological situation bulletins and information on the evolution of water levels . In 1994, 54 flood warning services monitored 16,000 km of waterways in France using automated measurement networks.