The hydrogeological situation after salt-mine collapses at Solotvyno, Ukraine

Study region The study site is located in the south-western part of the Ukraine, in the area of the historical rock-salt mining town Solotvyno. The former mining area is situated in close vicinity to the River Tisza, the main tributary of the Danube River, the largest river in Europe. Study focus After uncontrolled flooding of several salt mines, a one month advisory mission was launched by the European Commission to estimate the impact of the abandoned salt mines (containing large quantities of salt water) on the environment. As a consequence of the flooding, dozens of sinkholes formed and sinkhole forming processes are ongoing, with sinkhole diameters reaching 250 m. As river contamination by the release of large quantities of saltwater would lead to an international disaster, hydrogeological measurements were taken on-site to study the system. New hydrological insights of the region At the study site, saturated (hyper-saline) water as well as fresh surface and groundwater were encountered in close vicinity to each other. Electrical conductivity, as a proxy for salinity, and temperature were measured on-site and water samples taken from surface-, ground- and mine waters were analyzed for chemistry and stable isotopes, providing new insights into groundwater flow dynamics. A conceptual model shows the salt dome, and potential flow paths from the mining area to the Tisza River, in the context of the mines and associated sinkholes potentially impacting the river water quality.