Primary Studies for the Presence of Offshore Freshened Groundwater in the Bulgarian Black Sea Shelf

Abstract

The groundwaters draining in the continental shelf area can be an unconventional resource of fresh water for drinking, irrigation, and industrial purposes in water-scarce coastal areas. Recently, possible offshore sources of such groundwater in the coastal zone have been subject of increased investigation and description. The aim of the present research is to identify similar, available for use, potential sources of Offshore Frehsened Groundwater (OFG) in the area of the shelf of the Northern part of the Bulgarian Black Sea coast. In the watershed of this region, which has the least rainfall in the country, there is almost no surface runoff, the rainfall mainly feeds the groundwater. A hydrogeological analysis of the region was carried out to identify potential submarine sources of fresh groundwater. 40 years ago in that shelf area, on the basis of temperature and mineralization anomalies of the seafloor waters, continental Submarine Groundwater Discharge (SGD) zones were established. The present studies, based on the detection of anomalies in the distribution of bottom and surface sea water temperature in the area, were carried out to confirm the then established data on the availability of potential submarine sources of fresh water. For this purpose, data from observation obtained by modern high-tech means were used. Sea Surface Temperature (SST) mapping and water contrast plume zones establishment was conducted for Northern Bulgaria by applying a high-resolution satellite product (GHRSST, CNR MED Sea Surface Temperature) from the NASA data-set. The locations of mapped potential groundwater discharge determined by the present SST study are consistent with those previously estimated. The study is the basis for further research, local sampling to assess the existence and magnitude of the Offshore Freshened Groundwater (OFG) and its potential utility.