45. HPP Ombla in Croatia – Proposed Use of Energy from Groundwater in Karsf Aquifer

In order to determine the zones of increased permeability of the rock mass and locate all active and fossil cave conduits, an investigation adit was built in the dam profile, along which the investigation boreholes were made in order to determine permeability of the rock mass layers under the sea level. Detailed mapping has revealed structural relations in the area planned for future power plant structures. Particularly interesting are the fault zones along the grout curtain section. Hole potting and scuba diving investigations were initiated to determine all passable fossil cave rooms and caverns, particularly the main cave conduit through which about 95% of the Ombla water is discharged. Results of all the investigations have confirmed that the immediate hinterland of the Ombla spring is suitable for impoundment of an underground reservoir which would enable conservation of significant quantities of water used for power generation and potable water supply and for export into the Mediterranean countries.