The salinity of the springs varies over time depending on discharge; the salinity comes from great depth below sea level, from land that is several kilometers inland. The Port Miou observation site is unique for the study of coastal karst; it is an artificial tunnel that permits access to an underground drowned gallery 500 meters from the sea, within the land. Measurements are conducted on water (CTD, fluorescence, water isotopes, major ions) and on reservoir rocks (morphologic evolution of karst, 3D structures, geochemistry) at the scale of the regional hydrosystem. The springs are part of the network of hydrogeologic measurements established by CEREGE within the KarstEAU project (www.karsteau.fr).
Coastal karst springs are the subject of specialized study. They are characterized by brackish water of variable salinity that acts as a natural marker making it possible to study both the hydrodynamic functioning of the karst and the saline intrusion mechanism. Because of their location in a littoral zone, these springs are also the outlet of aquifers that constitute a strategic water resource for growing populations in the Mediterranean region. Long-term evolution of discharges and groundwater salinity is directly related to global change (climate, eustatic variations). Coastal springs are the result of a) flow and transport processes on the continent determined by the spring’s drainage basin and b) interaction with the sea, which enters the land at depth and receives the fresh or brackish water contribution in the littoral zone.
The Port-Miou hydrosystem contributes to the following objectives: