Lake and sea in closest vicinity – that is how we might describe Vransko Lake – the largest natural lake in Croatia. Immersed in the Mediterranean climate, but by no means deep – for the lake is two to five meters deep at the most – Vransko Lake is a natural phenomenon of a submerged karst field full of life.
In terms of its position and characteristics, the lake is truly a special phenomenon in Croatia, but also in a wider European area. It is a natural cryptodepression, a phenomenon creating a unique lake life.
Essentially, it is a geographical phenomenon in which the surface of water in the lake is above the sea level, while the bottom of the lake is below the sea level. Underneath a considerable deposit of sludge, which exceeds 20 meters in some areas, there is an impermeable flysch rock layer. It serves as a barrier preventing water from disappearing into the karst soil. A narrow karst ridge between the lake and the sea is another natural barrier protecting the lake. However, due to the porous nature of the ridge, seawater enters the lake and increases the salinity.
Life can be pretty noisy here, and you can clearly hear it in the sound of birds. The lake is a special ornithological reserve, after all, with over one hundred thousand water birds wintering in the area.
Due to the conservation of a substantial area of reed surfaces and endangered wetland habitats, the lake is an ornithological paradise. It is included in the list of Important Bird Areas in Europe, and the Ramsar List of Wetlands of International Importance.
The ecological value of the area is immense, abundantly providing everything necessary for the life of plants and animals, which can thrive in diversity.
The area of the Vransko Jezero Nature Park is partly covered by bulrush, sedge and reed, and it reminds of grasslands interspersed by shallow pools of water and flowers with butterflies flying around. There are also dragonflies and numerous insect species. The entirety of life present in the area is constituent part of the ecosystem that is equally dynamic throughout the year.
Bird lovers will undoubtedly cherish their visit an unforgettable experience. From hiding places, one can observe the life of birds, their nesting and care for the nestlings. The entire lifecycle is on display, for everyone to see. Vransko Lake is a treasure of ornithofauna, with 256 bird species recorded so far, over one hundred of them nesting in the territory of the Nature Park.
When it comes to nesting birds, four species present in the area are endangered at the European level, and seven species are endangered at the level of Croatia.
The lake is one of the few nesting sites of endangered species purple heron and pygmy cormorant in Croatia.
Ornithological reserve is the most valuable part of the Park in both biological and ecological terms. Many migrating birds rest and feed in the reserve during the period of migrations from cold European areas into warm African lands (and back).
Some bird species are present in the Park in large numbers, which is an indication of the fact that wetland habitats face increasing threats throughout Europe.
Subjected to destruction, perceived as undesirable, wetlands in Europe have decreased considerably in terms of surface. That is why Vransko Lake is a European oasis as well. The surface of Vransko Lake itself used to be larger in the past, with some wetland areas gradually transformed into fertile agricultural land by reclaiming, in order to plant vegetables and field crops. This land awards the efforts of people in the region of Ravni Kotari with good yields. A number of constant water sources, the sun and the mild nature of the Mediterranean climate provide ideal conditions for agriculture.
The water is abundant with fish. There is hardly an angler not acquainted with these waters. It is general knowledge that people come here to catch carp, catfish and pike – species that make this lake a fishing Mecca.
Eel, which is the only autochthonous fish species of the lake together with freshwater blenny, is strictly protected in the area of the Nature Park. This fish is a true natural phenomenon. It spawns in the distant Sargasso Sea in the North Atlantic. Small young eels travel towards our coast from that part of the world, using the warm Gulf Stream, eventually reaching Vransko Lake. Once they reach sexual maturity, they return to the northern waters, where they die upon spawning.
Brackish water provides habitat to a unique combination of marine and freshwater species, which makes the area highly attractive for fishermen globally. Vransko Lake is connected with the sea by a man-made channel of Prosika, which was dug out back in 1781, and connects the lake with the bay of Pirovac.
The passage was made in order to enable drainage of surplus water during the rainy periods, which was important in order to prevent flooding of the Vransko polje area.
However, the construction of the channel of Prosika brought certain biological and ecological changes to the lake. In the periods of lower water levels, for example, seawater flows into the lake to a higher extent, changing chemical and biological properties of water, and affecting the plant and animal world as well.
The lake receives its water from several sources. The most important ones are: Škorobić, Vrilo, Biba and Pećina. The sources of Pećina and Škorobić are located in the settlement of Vrana, which gave Vransko Lake its name.
Description of the lake in terms of numbers would be as follows: it is over 13 kilometers long, on average four meters deep, and its surface is approximately 30 square kilometers. The annual water level fluctuation does not exceed two meters, and the average fluctuation is one meter.
The panorama trail around the lake is forty kilometers long, which is why Vransko Lake is a destination of choice for many cyclists. Visitors who decide to enjoy a walk frequently stop at the little port of Prosika, enjoying the opportunity to rest in nature and gathering the energy to walk to the sightseeing point of Kamenjak, which awards visitors with a rare opportunity – a spectacular panorama of both the lake and the Dalmatian islands.
The specific position of Vransko Lake right by the sea is the source of all its attractions and its abundant biodiversity. The lake is surrounded by the Kosovac plateau, the ridge up to 110 meters high dividing it from the sea, and, a bit further away, there is also the Velebit Mountain, with its as yet insufficiently researched impact on the hydrology of the Nature Park.
The unique position of the lake has been attracting people since ancient times. It was appreciated and respected by the cultures of Liburnians, ancient Romans, Croats, Ottomans and Venetians, as can be seen in archaeological findings.
The lake, with everything that it offers, guarantees a special experience. Completely different and yet compatible landscapes are there for visitors who wish to experience the joy of spending time in nature. The sea and the islands, Mediterranean wetlands, rural heritage of the region of Ravni Kotari... It would not be wrong to conclude that Vransko Lake is a safe bet for demanding visitors, those who are hard to please, and who want to enjoy as many experiences as possible in one single, relatively small area. Such visitors will not make a mistake by coming here. However, Vransko Lake is also a good destination for those who do not like to plan everything in advance, because it is an unusually rewarding place, and a great starting point for exploration of surrounding areas. In a moment, one can visit a Dalmatian island, go back to fishing, with both marine and freshwater fish available – or take a break and enjoy the abundance of agricultural production of the area of Ravni Kotari.
Freshwater expanses of the lake hide underwater plants from the family of Charophyta, similar to field horsetail in their appearance. Widespread reed represents one of the key habitats of the area, and plays a very important role: water purification. Due to its size, reed extracts nutrients it requires for growth from the water, thus preventing the nutrient surplus from agricultural land in the Vransko Lake basin from reaching the lake itself. Without this function of reed, many rare and threatened animal and plant species could not live in this ecosystem. On the northern shores of the lake one comes across the opposite landscape, in the form of dry grassland habitats seductive in their aroma of sage, curry plant and heather.There are 95 protected species in the area of the Park, and 51 strictly protected plant taxa. Habitat that can be found on the lake shores – wetland and floodplain meadows – are not natural ecosystems. They were created by man, as a result of mowing or livestock grazing, and that enabled the growth of rare plants that cannot be found in forests or thicket. Most of the shore zone of the lake is covered by a belt of dense reed.
Given the extent of wetlands and wet habitats, Vransko Lake is an important home to amphibians. Eight amphibian species are present in the area, three of them part of the Red List of Croatia. All eight species are threatened at the level of Europe, and most of them are protected by law. The most numerous amphibians in the area include marsh frog (Rana ridibunda), tree frog (Hyla arborea), agile frog (Rana dalmatina) and toads (Bufo sp.). Less frequent species are the fire salamander (Salamandra salamandra), smooth newt (Triturus vulgaris) and yellow-bellied toad (Bombina variegata).
One peculiarity of the Vransko Lake is the diversity of habitats highly favorable for reptiles, with 20 reptile species living in the area of the lake. Some of the best-known reptile species one can encounter here are the European pond turtle (Emys orbicularis) and Hermann’s tortoise (Testudo hermanni). Lizards are also present – such as sheltopusik (Ophisaurus apodus), the Italian wall lizard (Podarcis sicula), the Balkan green lizard (Lacerta trilineata), common wall gecko (Tarentola mauritanica). Snake species include the Balkan whip snake (Coluber gemonensis), Aesculapian snake (Elaphe longissima), grass snake (Natrix natrix), dice snake (Natrix tesselata), horned viper (Vipera ammodytes) and several other species. All reptile species with the exception of horned viper are protected by law.
Muddy and pebbly shores are mostly located in the shallow northwestern part of the Ornithological Reserve. Drop in water levels during the autumn period results in the creation of sandbanks and zones with varying water depth, providing feeding opportunities to a number of water birds. Waders, egrets and herons, spoonbills and ibises are wading birds that feed by wading through shallow water and the shores. Since they are not competing with each other, and there is enough food on the attractive muddy table for all, one can also see various calidrids, sandpipers and other waders feeding together in shallow waters up to 20 centimeters deep. A Nature Park trademark of sorts is a large bird with snake-like neck, called purple heron (Ardea purpurea). Long legs enable the purple heron to engage in successful hunting and feeding by wading through the canals and flooded reed beds. Her Croatian name danguba, meaning do-nothing, was given to the species in a rather unfair manner, due to the fact that the bird is astoundingly patient and does not move for very long periods as it stands in shallow water and lurks the prey: fish, insects and amphibians. The nesting of this species is extremely sensitive and requires a constant water column level in reed beds, which is why survival of the nesting purple heron population in the lake area, as the only population of this species in the coastal part of Croatia, depends on sufficient inputs of water into the lake. The biggest threats are posed by the destruction and drainage of wetland areas.
Numerous archaeological sites on Vransko Lake testify to the importance of this Mediterranean wetland for human presence. The waters of Vransko Lake were an inspiration to many civilizations, ranging from the Liburnians living here when the lake first got its name, to the republics, empires and kingdoms of the Romans, ancient Croats, Turks and Venetians.
In the 4th century, a Roman aqueduct supplied fresh water from the source of Pećina near the village of Vrana to the city of Zadar 40 kilometers away. This water supply system was used to provide water not only to Zadar, but also to various villae rusticae, Roman agricultural estates, along the route. According to the preserved records and maps, Vransko Lake was a very important site in the network of Roman public roads, such as the road of Scardona leading from Nin to Skradin, a very busy road built in a straight line and passing along a number of wells that still carry their pre-Roman names.
In the immediate vicinity of the lake, the old town of Vrana was built in the Middle Ages. The Benedictine monastery in the area was the place where the insignia symbolizing the authority of the Croatian kingdom were long guarded within the walls, and the monastery was also used by the Knights Templar at one point. The Turkish inn owned by Jusuf Mašković from the 16th century, a motel of sorts of the ancient Islamic world, is located on the edge of today’s Nature Park and represents the westernmost monument of Islamic civil architecture in Europe.
Management of natural resources of Vransko Lake
The feudal system of the 18th century brought the first comprehensive water regime and fish management intervention to Vransko Lake, which was part of the feudal estate of Vrana back in those times. The hydrotechnical intervention was quite big, and it entailed the digging of the Prosika Channel and drainage of a considerable floodplain area of Vransko polje, coupled with its intensive cultivation.
Franjo Borelli (1704-1762), son of Bartul Borelli, the Captain of the Fortress of Knin, got the feudal estate of Vrana in 1752. Back in those days, the estate was in effect a swamp full of thorns and bushes, and it was completely neglected. The new landowner decided to implement a visionary idea of putting the estate to order by melioration of the field of Vransko. He succeeded in this endeavor after 18 years of work, following major efforts invested in the project by him and his heirs. After the channel of Prosika was dug out in 1770, the level of Vransko Lake fell by three meters, and a major water wave left its trace on the sea surface all the way to the settlement of Betina on the nearby island of Murter.
Simultaneously with the digging of the channel and after that intervention, the melioration of Vransko polje on the northwest was performed under the supervision of the best engineers available. These works enabled a true renaissance of the estate of Vrana, which became a role model of a large, modern, well-managed estate. Towards the end of the 19th century, due to insufficient capacity, the channel was slightly deepened, and the final profile of the channel, eight meters wide, with the top level 30 centimeters above the sea level, was constructed in 1948. Initially, the channel was considerably shallower, and its width was four meters.
The surrounding area of Modrave, intersected by the channel of Prosika, is a narrow land isthmus between the sea and Vransko Lake, with the surface of 12 square kilometers. Hundreds of stone walls, piles and paths of Modrave, elegantly intertwined in a giant network that resembles lace made of stone, represent a monumental achievement of the people of Betina and Murter. Towards the beginning of the 20th century, with their extraordinary skill and immensely hard work, they put order into the barren karst landscape, and planted and cultivated thousands of grapevines and olive, fig and sour cherry trees. In less than 50 years, they thus created what used to be the most compact and the most beautiful olive grove on the eastern Adriatic coast.