Buna Spring in Blagaj remains partially unexplored by divers

Divers exploring the Buna Spring in Blagaj, located 12 kilometers from Mostar, have reached depths of 72 meters without discovering the end of the underground system. Considered one of the strongest karst springs in Europe, the Buna emerges suddenly from a cave opening beneath a high cliff.

The spring's flow varies significantly depending on the season. According to the International Union of Geological Sciences (IUGS), the average discharge is approximately 23.7 cubic meters per second. During summer droughts, this can drop to 3 cubic meters per second, while rainy periods can see flows reach 120 cubic meters per second. A historical record from January 1971 noted a peak discharge of 380 cubic meters per second.

The water originates from precipitation on the karst plateaus above Mostar, traveling through underground channels across an area of about 1,100 square kilometers. This process keeps the water temperature consistent at around 10 to 11 degrees Celsius. While expeditions have mapped about 520 meters of flooded channels since 1973, the exact source and full path of the water remain unknown.