Very good question Dr Veerasingam. Many works have been published since the middle of 90's on the submarine groundwater discharge in coastal zone, mainly through the development of radiotracer to quantify this SGD (but not only). In some case, SGD have been proposed as an important source, but it generally corresponds to karstic area. Most of the time, SGD are in fact assocaited to brackish waters due to mixing between fresh and salt water within a saltwedge, below the coastal interface. So, the fluxes of water and of some dissolved coumpounds could be important, but it's often with brackish and not freshwater. But it could be different from on coast to another, mainly depending on the type of coastal aquifers.

Dear Dr. Olivier Radakovitch,

Thanks for your discussion. Yes, radio tracers including 222Rn and 226Ra are widely used to quantify the SGD. But if we go through the history of SGD, the offshore discharge of freshwater has been investigated and used in a number of cases for water resource purposes. One particularly spectacular example of such use involved the construction of dams in the sea near the southeastern coast of Greece. Moreover, people lived before 2000 years in Syria were aware about SGD and they collected freshwater from near the island of Aradus in the Mediterranean by boat, utilizing a lead funnel and leather tube, and transported to the city as a source of freshwater (Burnett et al., 2006). If they executed successfully long back, then why can't we do now? What are the bottlenecks to achieve this?

Regards

Veerasingam

Dear Colleagues,

if I understand well this small discussion about marine sea water influence on the coastal areas of fresh water origin. Except of direct experiments such influence can be checked by biological indicators. I used this possibility during investigation of the Sassyk Reservoir in Odessa Province in Ukraine that is simply the uniqe experiment of transformation the sea bay (liman in local slang) into fresh water reservoir. During the summer time or even hot season it is hardly cheked the influence of the sea but in winter, when ice catch the surface (under stratification) appear visible influence of  "grifons" that are salt springs with extremely high salinity. This completely reconsruct the ciliates benthic community, where appeare a lot of marine species! So, we have to do with impulse-stabilised ecosystem. the fact was'nt take into consideration when project had been prepared< that produce giant economical losses, as water from liman was used for watering of closely near areas of grapes. detailed explanation in book consecrated to Sassyk in my list, sorry, in Russian.

Your's,

Andrey