Stručni rad
The water-supply system and roman aqueduct situated on the small hill of Gradina on the island of Veliki Brijun
Anton Vitasović
Sažetak
The water -supply system and roman
aqueduct situated on the small hill of Gradina
on the island of Veliki Brijun
Anton VITASOVIĆ
In 1979, a survey of a Roman well and a Roman wool mill on the island of Veliki Brijun
was carried out. The research confirmed the then known data and also yielded new results.
Both the previous and new data indicated that there was a Roman aqueduct situated on the
small hill of Gradina. The aqueduct consisted of two water reservoirs, and a facility constructed
above a precipice. The investigations once again revealed the presence of a flight of steps. A 16
m long water pipe was also recovered from a layer of mortar. According to A. Gnirs, lead pipes
were part of the aqueduct system and were also used as outlets. The pipes were still in place at
the end of the Second World War, and then disappeared, while their imprints were observed
on the terrain, along with obvious signs of devastation. In the course of the investigation,
the second cistern was cleared of debris, and the terrain surrounding the mentioned facility
and the reservoirs was excavated. This brought to light an even more complex facility than
the one previously known.
From the architectural point of view, three construction phases were noted, as well as several
smaller reconstructions. In essence, there was a natural spring, an aqueduct constructed above
ground, and aqueduct installations with a pumping station and reservoirs. The natural spring
is situated inside the third defensive circle of the Gradina settlement, and was used by the
hillfort settlers. An above-ground water flow was constructed, starting from the spring and
running through a wooden channel set between two lines of wooden supports. In the second
construction phase, this above-ground water flow was rearranged and used to set in motion
the wool-mill installations. In the third construction phase, a natural precipice was utilised and
a pumping station with reservoirs was built, as was the water-supply piping and the substation
(the aqueduct). Apart from the pumping station and the reservoirs, there are also the remains
of the pertaining water-supply piping, though present only in fragments, on the small hill of
Gradina. The investigation showed that the area holding the water pumping installation was
1.6 m above the bottom of the reservoir. The recovered stone base with an axis slot, and the
way the space was arranged, indicate that there were two cylindrical devices mounted on the
same axis. The left cylindrical device was a hollow construction connected by foot pedals for
those who powered the installation. The right cylindrical device was narrower and mounted over the well. Its structure was connected by short, round, wooden bars, over which a chain
with buckets would be lifted. The water would be tipped into the reservoirs, and through
the pipes conveyed to its final destination. Since the well was not investigated all the way to
the bottom, its depth is unknown. Consequently, the possible use and the quantity of water
in the well remain unknown. From 1950 to 1954, geological surveys were conducted on the
island of Veliki Brijun, and wells were drilled. Numerous fresh water deposits were found at
depths of 20 to 300 metres1. The Romans were not aware of these deposits, so they extracted
rocks and constructed terraces for the collection of rainwater around the water pumping site.
The collected rainwater on the northern slope of the small hill of Gradina was conveyed to
the well. The aqueduct reservoirs, cisterns and reservoirs of the Roman villa situated in the
cove of Verige, could hold more than 1,450 m3 of water. Their combined capacity was larger
than the capacity of the water supply system of the entire city of Colonia Pola. This indicates
a rich and abundant use of water for a variety of purposes.
The mentioned surveys corroborated once again, although modifying slightly, the
conclusions regarding the water outlets from the reservoirs and the directions of the water
conduits from the reservoirs. The exact turning points of the left and right arms of the
aqueduct were established. The arm travelling straight and arriving at the thermae had already
been known from the survey conducted by Gnirs. The presence of the steps and of a tunnel
dug up in the live rock attested to the fact that the facility could be reached from the north
and northeast. The most important results of the survey conducted in 1979 were certainly
the opportunity to reconstruct the way the water was pumped, the discovery of the base
of the above-ground aqueduct, and confirmation that the aqueduct was used even after
the third construction phase when the well and reservoirs had been built. According to the
systems and approaches applied to water use, the water resources were exploited carefully
and circumspectly. From the technical point of view, the approach to the problem of water
supply and the solutions applied make the Roman aqueduct on the island of Veliki Brijun a
rather modern installation. Since the precipice has not been fully investigated, data on fresh
water deposits are unknown and, consequently, the potentials of the well are also obscure.
Water collection terraces on the northern slope of the small hill, the water capacity of the
substations built for high impact water users, and the water capacity of the cisterns for the
collection of rain water all raise questions about the availability of fresh water deposits on
the island. Taking into consideration all the available data, a conclusion can be drawn that
the aqueduct on the small hill of Gradina was not functional throughout the year, but was
used occasionally for the needs of the wool mill and to supplement the water capacity of the
substations and cisterns.
1 Geological surveys on the island of Veliki Brijun, reports and minutes of the handover and acceptance, NP
Brijuni documents
Ključne riječi
Hrčak ID:
34472
URI
Datum izdavanja:
15.11.2008.
Posjeta: 4.290 *