Ombla River

A few kilometres inland from Dubrovnik, tucked behind a bend in the Rijeka Dubrovačka inlet, sits one of the odder natural landmarks on this coast: the Ombla River, one of the shortest rivers on Earth at roughly 30 metres long — by some counts the fourth shortest in the world. It has a source, a course and a mouth like any other river, except that you can take all three in from a single spot.

A River With No Middle

The Ombla emerges fully formed from a large karst spring at the foot of the Golubov Kamen massif, a 422-metre ridge straddling the border between Croatia and Bosnia and Herzegovina. It is one of the biggest karst springs in Croatia and among the largest in the Dinaric Alps, rising out of a cave roughly 80 by 40 metres across, with about eight metres of clearance between the water surface and the cave roof. The primary source lies some 15 metres below sea level, with secondary outlets a couple of metres above it.

Despite its tiny visible length, the river drains a basin estimated at 600 to 900 square kilometres, reaching as far inland as Popovo Polje in Bosnia and Herzegovina and taking in around 176 settlements, with an average discharge of 24.1 cubic metres per second. That figure swings enormously with the seasons, from under four cubic metres per second in a dry summer to more than a hundred after heavy winter rain. Essentially everything the mountains behind Dubrovnik absorb comes back out here.

From the spring the water runs its short course into Rijeka Dubrovačka, a ria — a drowned river valley — forming a sheltered inlet about five kilometres long that opens into the Adriatic just west of the old city. The river's older name, Arion, comes down from classical antiquity, when it referred to a longer watercourse rising and sinking through the karst of present-day Herzegovina before resurfacing at the coast; it appears in the Periplus of Pseudo-Scylax, the earliest known reference to the river. Where the name Ombla itself came from, nobody has satisfactorily explained.

Dubrovnik's Water

Fresh water has always been the binding constraint on this limestone coast, and the springs of the Rijeka Dubrovačka valley solved the problem for the medieval Republic. In 1436 the city commissioned the Neapolitan engineer Onofrio della Cava to build an aqueduct, and by 1438 water was running along some twelve kilometres of stone channel and buried pipe from the valley into the walled town, arriving at the domed fountain on the Stradun that still carries Onofrio's name. The whole system worked by gravity, without a single pump.

The Ombla spring itself was brought into the network considerably later. The first contract to draw water from the river was signed in 1897, for 960 cubic metres a day, with the owner of watermills operating on it. The intake plant at Komolac has since grown into the city's principal source, and modern pumping means Dubrovnik now drinks from the same spring that once turned those mill wheels.

The Cave and Its Inhabitants

The spring's cave system is also home to a rare find: juvenile specimens of the olm, a blind, cave-dwelling amphibian, discovered here at what's recorded as the southernmost point in Europe where the species has turned up. Three young animals were found during a joint speleological and biospeleological survey carried out by an international team of cave divers at the source. The same survey documented a large population of the Popovo minnow, reported as the biggest known anywhere in its range across Croatia and Bosnia and Herzegovina.

That biodiversity fed straight into a long argument over a proposed hydroelectric plant at the spring, a scheme that would have dammed the underground reservoir. It secured a loan of 123.2 million euros from the European Bank for Reconstruction and Development in November 2011, but the bank cancelled the loan in May 2013, citing environmental concerns after conservation groups objected to the likely impact on the cave system and the species living in it. The plant was never built.

Sailing In

The river flows past Komolac and into the Rijeka Dubrovačka, and it's one of the anchorages you'll visit on a private gulet charter from Dubrovnik — a green, sheltered stretch of water a world away from the open Adriatic. The inlet is the safest shelter for a long way in either direction: the marina at Komolac, laid out around the Renaissance summer residence of the Sorkočević family, sits roughly six kilometres from the old city and is the only marina between Korčula and the Montenegrin border, with several hundred berths in water protected from every prevailing wind. The valley around it is lined with the summer villas of Dubrovnik's fifteenth and sixteenth-century patricians, built here precisely because of the fresh water and the shade — the same two things that make it a comfortable overnight stop today.