Author(s): Vassilios K. Kaleris
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Keywords: Submarine groundwater discharge; Density driven flow; Cell model; Mixing; Near shore sea water
Abstract: Submarine Groundwater Discharge (SGD) transfers dissolved solutes, such as nutrients, organics, metals and pathogens, which can induce chemical and biological effects in the near shore sea water. Coastal zone managers have often the responsibility to decide whether SGD is of importance in the area of interest. Key issues for this decision are: (a) the magnitude of SGD as well as the pollutant load, which it transfers to the sea and (b) the intensity of mixing and circulation in the near shore sea area. An extensive review of methods to estimate the magnitude of SGD has been presented by Burnett et al. (2006). In the present paper results of numerical simulations are presented, which enable the estimation of the magnitude of SGD in the case of aquifers with simple geometry and geology. In the configuration considered, SGD consists of two components: (a) the flux of the land derived groundwater towards the sea and (b) the recirculated saltwater intruding the aquifer at its lower part. Despite the fact that the herein reported results can provide only rough estimates in actual situations, they are useful for the estimation of the probable effect of SGD on the quality of the near shore sea water. We showed, using a simple cell model (well-mixed reservoir model), that the probable maximal concentration into the near shore sea water of pollutants transferred by the groundwater depends on the relation between the flux of the land derived groundwater and the inflow of water from the open ocean into the near shore sea. The results show that the quality of the near shore sea water is, in the long term, influenced only by the flux of the land derived groundwater and not by the total SGD. Further, the flux of the land derived groundwater is of actual importance only if it is of the same order of magnitude as the inflow from the open ocean into the near shore sea area. The other component of SGD, namely the recirculated sea water, influences the time at which the quality of the near shore sea water is affected. In turns, this time strongly depends on the relation between the volume of the near shore sea area and the storage capacity of the near shore part of the aquifer. This time may be particularly large (in the order of years) if the absorption capacity of the near shore aquifer is large.
Year: 2007