Evaluation of the impact by deep artesian boreholes on fresh ground waters in the terrace of Kamchiya River

The area of Kamchiya River’s inflow into the Black Sea has an important role not only as a natural landmark, but also as a leading factor for the national economy. It has been subjected for many years to oil and gas exploration, as well as to extraction of deep, highly mineralized waters containing chemical elements of industrial value. There are currently only few of the artesian wells related to these activities in the area. Outflowing water has very high mineralization (over 50 g/l). It is chlorine-sodium type and has extremely high concentrations of some components. They have formed small salt ponds around the wells, whose water and salt balance are controlled by the evaporated and infiltrated in depth water quantities. The abrupt change in the thermodynamic conditions in the porous part of the wells favours the processes of sedimentation and deposition of a substance that partially refreshes the leaking surface water and limits the possibilities for infiltration of highly mineralized waters. Salt infiltration causes enhanced local salinization of the soils and fresh groundwater accumulation in the present-day sediments of the Kamchiya River. An assessment of both the dimensions and extent of salinization in the area of the deep wells is made by applying hydrochemical and geoelectrical survey.