The Ombla River, which is one of the shortest rivers in the world, is part of the Adriatic catchament area. The spring of the river Ombla is located in the area of Dubrovnik- Neretva County, north of Dubrovnik, in the town of Komolac at the foot of the rocky mountain massif known as Golubov Kamen. With its apperance and abundance, it represents a karst phenomenon that was created at the contact of carbonate deposits on top of a complex of Eocene flysch deposits. Viewed more broadly, it belongs to the Trebišnjica river catchament, which is one of the most interesting karst areas in Europe due to its wealth of natural features. Because of the construction of the Trebišnjica hydropower system, the waters of the intermediate Ombla catchment area are retained in reservoirs. They are then directed through tunnels to the downstream hydroelectric power plants, which has caused a change in the natural water regime of this source. Safe drinking water is a necessity for every individual, and the need for it is increasing day by day. Fortunately, Croatia is a country rich in water, and so is the entire Dubrovnik area. The source of the Ombla River is one of the richest karst springs. With its capacity of 520 l/s during maximum consumption it exceeds the entire drinking water needs of the town of Dubrovnik and the Dubrovnik coast. Water is not only a commercial product, but also a common good and a limited resource that needs to be protected and used in a sustainable way. For this reason, it is necessary to monitor the state of its quality and quantity and to act accordingly. The paper presents a hydrogeological description of the Ombla basin and its spring as well as the data which are necessary for the analysis of the amount of water outflow and the quality of raw water at the spring of the River Ombla.