Hydrology

Hydraulic structure fed by water withdrawals from watercourses or bodies of water and mainly intended for navigation, drainage, irrigation or flow regulation.

Amount of soil water below which a plant wilts. The irrigation doses are calculated from the easily usable water reserve (RFU) and we irrigate when the latter is exhausted. It is expressed in mm.

All changes in the status and characteristics of an aquatic environment which regularly recur in time and space and go through cyclical variations, e.g. seasonal variations.

Difference between precipitation and actual evapotranspiration and expressed in mm. Effective rainfall can be calculated directly from climatic parameters and easily used available water (RFU). The water of effective rainfall is distributed to the ground surface into two fractions: runoff and infiltration.

Value of the interannual flow converted into mm.

Amount of water passing through the soil surface. The infiltration phenomenon recharges groundwater and maintains the groundwater flow in permeable hydrogeological formations in the sub-soil. Compared with surface water flow, the groundwater flow can be slow, delayed and long-term (a few hours to several thousands of years).

Periodic oscillation of sea level. Swell occurs sporadically, depending on unequal pressures and friction of the wind, and is generated by these differences in pressure. It is formed by the wind far away from the observation area, and has a substantially sinusoidal oscillation profile, thus very regular, and spreads over long distances, unlike the

Difference between the average water depth of rainfall in the basin and the equivalent depth of runoff. It can be considered, in a first approximation, as actual evapotranspiration.

Current created at the immediate border of the coastline by the supply of water by oblique waves. It may be important in the Mediterranean, because of the lack of tidal current in particular. It can set in motion sand particles.

Terrestrial part of the coastal area whose influence on the water quality of the marine part is the strongest. This part is the smallest sub-area of the natural cachtment area.