Hydrology

Phenomenon where an internal wave reaching the coast causes a rise, sometimes very high (up to 2 m) and lasting long enough, of the instantaneous mean sea level.

Minimum flow possibly increased with the authorized withdrawals on the influenced section. It is expressed in the specifications and water regulations in particular. Often mistakenly used instead of minimum flow.

Value of the mean monthly flow at the nodal point (key management point) above which we consider that all uses (activities, abstractions, discharges, etc) made

Fraction of a volume of surface or ground water, withdrawn and not returned to the aquatic environment (river or aquifer), i.e. not discharged after use (water used by plants and evapotranspiration, evaporation, etc.).

Ratio, in a given place, of the mean tidal range in spring tides. This number, expressed in hundredths, is applied to the tides on French coasts. It allows an approximate prediction of High and Low Tides. Tides whose coefficient is greater than 85 are called "spring tides" and those whose value is less than 55 are "neap tides". The concept of

Balance made on a given basin or sub-basin for a specific period between, on the one hand, the available resources, owing to foreseeable water inputs or income over the same area for the time period taking into account the necessary functioning of aquatic ecosystems, and, on the other, the water demands, i.e. the volumes or water

Adjective that describes the water-sediment interface (= water-lithosphere interface) of an aquatic ecosystem, regardless of its depth (the bottom of lakes or of rivers or of the sea). Also describes an organism living on the river bottom or sea bed (macroinvertebrates, for example).

Underwater equivalent of topography, i.e. description of the immersed relief through the study of the nature of the bottom of an aquatic environment and its depth. The results of these studies are drawn into bathymetric maps.

Reappearance above ground of water infiltrated in limestone rock in the form of a spring.