Istanbul Water Culture

 

While the Workers' and Labourers' Day is celebrated on 1 May every year, the Bosphorus hosts the festive passage of bird migration. Tens of thousands of bird species, starting from Africa and travelling a total of 40 thousand kilometres to Europe via Istanbul and the Bosphorus, are found in the Bosphorus skies during this period. The Bosphorus sky is a paradise for many bird species, from raptors to passerines. The birds, which never pass Istanbul and the Bosphorus without drinking its water and eating its food, form a great migratory branch starting from South Africa, growing from various parts of Africa, to Antakya via Israel in the Middle East, and from there to Europe. Flocks of birds have been continuing their festive migration in the Bosphorus skies for millions of years. As a result, the birds of Europe also pass through the Bosphorus.

Being a Fish in the Bosphorus

The diversity of fish in the Bosphorus and the Sea of Marmara is frequently mentioned in historical sources. Karekin Efendi Deveciyan's Fish and Fisheries in Turkey, the first work on fisheries in Turkey, was written during his tenure as director of the Istanbul Fish House and chief inspector of fish affairs. This work was published in Ottoman Turkish in 1915 and in French in 1926.

Thanks to the detailed information and precise illustrations in Deveciyan's book, we can learn about the types of fish that Istanbulites consumed in the past. This book is an important source not only in the field of fisheries but also in folkloric studies.

The incredible flavour of Istanbul fish is attributed to the fact that the fish spend their spawning and growing periods in warm and shallow waters, as the Marmara Sea is an inland sea. In addition to this, the fish diversity is quite high thanks to the opportunities created by the two seas with different characteristics and the Bosphorus road connecting them.

However, today, some species are almost extinct and many fish species have decreased due to faulty fishing and marine pollution. Despite this, Istanbul is still an important fish centre.

Historical sources frequently mention the abundance of fish species in the waters of the Istanbul Strait and the Marmara Sea. The most comprehensive source on these fish species is the work of Karekin Efendi Deveciyan (1867-1964), who served as the director of the Istanbul Fish Market between 1910 and 1917 and later as the chief inspector of fish affairs. His work, titled "Fish and Fishing in Turkey," was first published in Ottoman Turkish in 1915, and an expanded version was published in French in 1926. It was the first study of its kind on fishing in Turkey.

The detailed information and precise drawings in Deveciyan's book provide not only unique insight into the fishing industry but also a valuable resource for folklore studies. One of the reasons for the incredible taste of Istanbul fish is that they spend their spawning and maturation periods in warm waters due to the Marmara Sea being an inland sea. Another reason is the diversity of fish species, which is abundant due to the opportunities created by the two different seas with different characteristics and the Bosphorus that connects them. However, unfortunately, some species have almost become extinct today, and many fish species have decreased due to incorrect fishing practices and sea pollution. Despite these challenges, Istanbul remains an important center for fishing.

Fish species in Istanbul can be divided into two categories: native and migratory. Migratory fish swim to the Black Sea to spawn every spring and return to the Marmara and Aegean Seas to spend the winter. However, the period when the fish pass through the Bosphorus is the fishing season for Istanbul. Native fish, on the other hand, are fish that live in Istanbul waters throughout the year, but their numbers have also decreased over the years. In the past, there were many fish species living in the waters of the Marmara and the Bosphorus, and they could be found in every season. However, it is impossible to say the same for some of the most popular fish species like bluefish, bonito, mackerel, red mullet, sea bream, gilt-head bream, and anchovy, which were once available throughout the year.

Some fish in Istanbul waters used to become fattier during certain seasons, and their grilled versions were highly preferred. Sea bass and sea bream were most delicious during August-October, and they could be consumed all year round, while pandora and annular sea bream were the preferred fish during June and July. Other fish species like horse mackerel were best between August and September, while red mullet, striped sea bream, hake, and whiting were most delicious in February, March, April, and May, respectively. Sardines, on the other hand, were enjoyed during July, August, September, and October.

As of May, the ancient inhabitant of the Bosphorus, the swordfish, which travels from the Aegean Sea and the Marmara to the Black Sea in the middle of summer and returns to the Marmara between September and November, is one of the lost legacies of the Bosphorus. Swordfish schools, which surface when the water warms up in April and stay for a while, were a source of entertainment and spectacle for Istanbulites. For the traditional fishermen, this period meant fishing time. We learn from Evliya Çelebi's 17th-century travelogue that the swordfish were traditionally caught in the Bosphorus weirs, particularly in the Beykoz weir section. After spearfishing gained significant industry-wide popularity from 1935 onwards, swordfish left the Bosphorus after the 1970s. This type, which has been boycotting Istanbulites, has been returning from the Çanakkale Strait to these parts since 1989.

When it comes to Istanbul's fish, it is impossible not to mention the weirs of the Bosphorus and the Golden Horn. The weirs, which are fishing spots, are large, wide fishing areas made up of nets stretched on piles driven into the water. It is known that in the Ottoman period, weirs were a widespread method of fishing in the Bosphorus. Weirs, established by fishermen since the 17th century, were fishing devices consisting of various nets arranged using many piles, ropes, and iron anchors, established on poles with wooden lookout posts and located three to four hundred meters offshore from the coast. Of the 53 weirs that existed in the Bosphorus in 1924, only the Beykoz, Filburnu, and Bağlaraltı weirs have survived to this day. The expression "strong like a weir boy," which has even entered our daily Turkish language, is used for young, athletic individuals with a strong gaze who observe schools of fish in the weirs. The Fish and Fishing book of the Fishery Minister Karakin Deveciyan contains detailed information about the Bosphorus and Golden Horn weirs.

Sebiller is an expression of loving the creature because of the Creator

There may or may not be any other examples like it in the world, but in many parts of Anatolia, including Istanbul, small birdhouses or bird mansions, known as "kuş evleri" or "kuş köşkleri" in Turkish, are present on the exterior walls of Ottoman-era architectural examples such as mosques, madrasas, fountains, and residential buildings. These elegant birdhouses or bird mansions are a magnificent example of aesthetics and appeal to a separate world as part of the architectural structure they exist in. These bird nests can be found as independent and impressive architectural elements on top of the buildings, or in the form of small nest-like spaces created between stones and bricks, or as simple wooden structures.

Istanbul's First Sea Baths Beaches

Beach culture arrived late in Istanbul, and the first encounter and adoption of this culture by the people of Istanbul started with the arrival of the White Russians who fled from Russia after the revolution. Over time, this culture spread among the people of Istanbul. The first implementation took place in Moda. It was the first indication of westernization. Beach culture developed and became one of the symbols of modernization from the early 1920s to the 1950s. While the first beach of the Ottoman period was formed on the shores of Moda, the beach of the Muslim population was the Altınkum Beach in Rumeli Kavağı and the Küçüksu Beach in Beykoz. Moda Beach was the only beach established directly as a beach, not as a conversion from a sea bath. The sea bath, a unique sea culture of Istanbul and the Muslims, was implemented in all Ottoman cities with a coast after Istanbul. The sea baths were in the form of simple shacks built on wooden piles nailed into the sea. They were open spaces that provided privacy when entering the sea. They were accessible by a thin dock from the coast. Besides the ones owned by mansions, those belonging to the municipality (Istanbul Municipality) were operated according to the understanding of the period by auctioning. The baths were divided into those for women and those for men, and there was always a seaside café near the men's baths or adjacent to them.

Reshad Ekrem Kocu, in Istanbul Encyclopedia, writes that the first sea bath was established between 1826 and 1850, and it was the Cardak Pier Sea Bath. In Seyahatname, Evliya Celebi mentions that in the 17th century, there were sea baths (derya hamams) for captains, and he also mentions a sea bath in Aksaray Langa and Eyup. Each sea bath had different features, just like traditional hamams. For example, in the late 18th century, it was known that there was a sea bath near Davud Pasha Pier, which was exclusive to merchants. By the 19th century, the number of sea baths had reached sixty, which were scattered over the coast of the Bosphorus, starting from Eyup and extending along the Golden Horn, besides famous sea baths such as Galata Bridge, Salipazari, and Kumkapi. Most of the sea baths were exclusive to women. Sea baths in Moda, Beylerbeyi, Salipazari, and Pasabahce were only allocated to women.

In Kadikoy, Buyukada, Buyukdere, Bebek, Kabatas, Uskudar, Cengelkoy, Yenikoy, Catladikapi, Yenikapi, Uskudar-Ayazma Pier, Heybeliada, Yenimahalle, Istinye, Kuruceşme, Kumkapi, Ortakoy, and Davutpasa, there were sea baths for both women and men side by side, and they were kept at a distance so that men would not approach to watch, and the police boat patrolled the area to prevent it. Although most of the large baths were allocated to men, the women's section was usually more crowded.

In 1929, when the coasts of Suadiye and Caddebostan, which were the new settlement areas of mansions, were organized as beaches, the most luxurious and expensive beaches on the Anatolian side were established. Then, in 1938, Fenerbahce beach was also put into service as a beach. With the construction of the Presidential Summer Residence, Florya Beach will become a popular place in the 1930s. Florya Beach has become a symbol of beach culture in the Republican era and will also take its place as Istanbul's largest and most modern beach. By 1957, Atakoy Beach, which has a capacity of four thousand people, will be opened. In the following years, Istanbul's coasts will be filled with beaches of various sizes until the sea water becomes noticeably polluted. Istanbul's beaches carry many interesting memories and stories. The expression "The public filled the beaches, and citizens couldn't go to the sea," which was uttered as a result of the intense interest of the public in the beaches, expressed the understanding of an era, knowingly or unknowingly.

Küçüksu Beach, one of Istanbul's first beaches, was created by arranging the alluvial sandy area between the Küçüksu Pavilion and Kibrislilar Yalisi as a beach area. The original owners of this area were the owners of Kibrislilar Yalisi. The mansion owners donated this beach area to the people of Istanbul. What a great display of courtesy and sacrifice. Today, many mansion owners take pride in their mansions...

A Civilisation that Pours Water After the Traveller

When departing from loved ones and leaving on a journey, it is customary to pour water behind the traveler during the farewell as a prayer and intention for a safe and speedy return. This act is considered a blessing and an expression of the value placed on the traveler. In some cultures, a fountain is built at the place of departure where people can gather to bid farewell to those embarking on a long journey. This fountain is called the Farewell Fountain and it serves to both send off and welcome travelers. It marks the boundary of the village and is an important part of the culture.

Istanbul, an ancient city that has hosted three different civilizations, also has its own Farewell Fountain known as Ayrilik Cesmesi. This fountain has been the last point of farewell for those departing from Istanbul for Hajj, military campaigns, the Surre procession carrying offerings to holy places, or those embarking on a long journey. The fountain is located at the last stop on the Asian side of Istanbul and its construction date and builder are unknown, but it is known that it was named Farewell Fountain because it was the place where people bid farewell to Istanbul.

The archaeological excavations in Yenikapi have revealed that Istanbul is, in fact, a city of water civilization with a history of over 8500 years. The discovery of 37 sunken ship remnants in the excavations has provided an important database for world maritime history. The excavations have also revealed information about ships carrying grain in the past and the trade of imported grain through ships that departed from Alexandria, Egypt and arrived at Theodosius Harbor in Istanbul. This demonstrates how Istanbul was sustained by its water civilization through the trade and transportation of goods.

Istanbul's water civilization was not limited to its own borders. It was a civilization that was nourished and influenced by both the Mediterranean and the Black Sea. This unique characteristic of Istanbul's water civilization has never been lost and continues to expand its borders today. Imagine a city where people can enjoy fish sandwiches by the water, a waterway that millions of people use to commute between work and home, a historic city with a dense population yet still maintaining its ancient water civilization. Istanbul is such a city and it still holds the distinction of having a water civilization with the Bosphorus waterway as a separate part of that civilization. In summary, Istanbul is a city of water civilization.

A Waterway Civilisation Bosphorus

The Bosphorus, which is the name given to the entire Asian and European coasts between the Black Sea and the Marmara Sea, has been expressed with many names in ancient sources. It was known as Halic-i bahri-rum, Halic-i bahr-i siyah, Halic-i Konstantiniye, İskender Boğazı, Konstantiniye Boğaz, Mecmaül-bahreyn, and İslanbol Boğazı, and today it is called Bosphorus in Western languages, which is an ancient Greek word meaning "ox passage."

The Istanbul Strait is a geological fault depression in terms of its formation. It is estimated that the valley, which was formed by the fault depression, was filled with water due to the rise of sea levels in the Black Sea and the Marmara Sea about 8,000 years ago.

The fact that the depth of the strait decreases from north to south suggests that the height of the southern entrance used to constitute an obstacle to the Marmara waters, but this obstacle was overcome as a result of the rise of sea levels. The Marmara Sea and the Dardanelles Strait were also formed as a result of geological fault depressions.

The Bosphorus Waterway is like an apple divided into two parts by hand, resembling two parts of a separated whole. If it were possible to unite the two coasts, it would have a topographical distinction that would perfectly match each other. This is why the Üsküdar promontory corresponds to the Dolmabahçe recess, the Ortaköy promontory to the Çengelköy Bay, the Kandilli Cape to the Bebek Bay, and the Yeniköy promontory to the Paşabahçe Bay. Throughout the entire Bosphorus waterway, there are twelve mutual bays and promontories, each with different geographic features and beauties.In the winding geographic structure of the Bosphorus, the water takes on another speed in the bay promontories where the waterway narrows, and the natural viewing terraces located on each of these peaks also add beauty to the scenery.

Whether we call it Bosforos, meaning "ox passage," or Halic-i Bahr-i Rum, the Bosphorus represents a civilization, and itself as a civilization.The Bosphorus is a gateway in every language. It is a gateway where the East and West, the northern and southern roads, the land and the sea cooperate. While being the gateway of the history of civilization, it witnessed the passage of humanity to the west, observed trade, was the last point of caravans, received taxes, and gave way to technological developments and transportation.While the winding structure surrounds the waterway, the high wide plains behind its steep slopes open up a second world to Istanbulites. These two worlds of the Bosphorus are a gift from Allah to the owners of this city. 

While we respond to this gift with all our ingratitude today, it does not come to mind the inability of the student of Aziz Mahmud Hüdayi to pluck a daisy on these Çamlıca hills.The Bosphorus has been known as a waterway that dates back to the depths of history. Phoenicians and ancient Greeks used this waterway, and even Greek colonies settled in the north of the strait.

Bosphorus Waterway and Currents

If the Bosphorus had been formed as a straight channel, transportation from the Black Sea to the Marmara or in reverse would not have been possible. The winding geographic structure of the Bosphorus and its currents provide transportation through the strait. The currents in the Bosphorus have been the sailors' nightmare for ages, as they have affected the ships' navigation since ancient times. However, these same currents also have a facilitating effect on the ships' easy access to the Golden Horn Port and passage through the Bosphorus. It is possible to find the most detailed information on these currents in the sources dating back to BC. Various information about the Bosphorus can be found in the works of Byzantine author Dionysos, as well as in the works of Herodotus, Polybios, Strabon, Plinius, Arrian, and Philostratus. The currents in the Bosphorus waterway are so variable and diverse that they have always been popular topics of myths and real stories. In general, it can be said that the Istanbul Bosphorus comes to life with four main currents. These currents take their names not from where they come, but from where they go, opposite to the direction of the winds, and they are sometimes powerful enough to stop sea transportation. The large north to south current in the Bosphorus is explained as the overflow of the Black Sea's excess water towards the Marmara. This current progresses from the north of the strait and heads to Kanlıca after Yeniköy on the European side, enters the narrowest part of the Bosphorus, and creates the "Devil's Current" in front of Rumelihisarı. Then it flows towards Kandilli Point, heads to Arnavutköy on the European side and flows close to the Asian side. It continues towards Sarayburnu from the Maiden's Tower and creates the "Maskara Current" in front of Kandilli. It flows from Beylerbeyi to Üsküdar and goes into the Marmara from Anatolia. This current, which has an average speed of five kilometers per hour, accelerates even more on days when the north winds are effective in the Bosphorus. Besides the upper current, there is also a lower current that continues from the Marmara to the Black Sea. This current, which is less speedy than the upper current, reaches its maximum speed of 1.22 kilometers per hour in Kuzguncuk. The salinity rate of the Bosphorus also varies according to these currents. The salinity rates of the lower and upper currents are entirely different. While the salinity rate of the water coming from the Black Sea is 17 per thousand, the salinity rate of the water from the Marmara is 35 per thousand. There is no other similar strait in the world like the Istanbul Bosphorus. One of the most challenging parts of sea transportation from the Mediterranean to the Black Sea and vice versa is the Istanbul Bosphorus. The completely different water regime beneath the strait also offers a livable life for Istanbul. The water coming from the Black Sea renews the surface of the Marmara every three months in this waterway, which is a natural cleaning...

Freezing of the Bosphorus

When it comes to the question of whether the Bosphorus Strait in Istanbul will freeze, the answer is that even during the coldest winter days, such an event seems impossible. Although the idea of the Bosphorus freezing and walking across the two shores seems quite impressive, the freezing of saltwater is quite difficult. The second most important factor is the continuous flow of currents in the Strait. For the Bosphorus to freeze, it needs to have a stagnant waterway in the first place. The Bosphorus Strait is both saltwater and has a constant current.

However, it is known that the Bosphorus has been covered in ice twice in history. This happened in 1929 and 1954 when giant icebergs broke off from the Tuna and Volga Rivers and covered the Bosphorus. It is also known that the Black Sea, which is like a closed lake, froze twice during the years 673 and 800-801.

Electricity Generation from Bosphorus Currents

The existence of opposing currents in the Bosphorus has been affecting the navigation of ships since the beginning of transportation from straits, which has drawn the attention of locals. The utilization of currents for energy production in the Bosphorus has been considered since the 1950s. Today, one of the projects being evaluated for the diversity of clean energy production in the future is the utilization of currents in the Istanbul Bosphorus for energy production. Electricity production through current and wave energy is a known and applied technology today. In this regard, projects are being developed for energy production through this method at the Arnavutköy burn in the Bosphorus.

Bosphorus Dwellings

The first settlements of Turks in the Bosphorus began with the construction of the Anatolian and Rumelian fortresses during the preparations for the conquest of Istanbul. These areas, which can be seen as the first neighborhoods inside the castle and its surroundings, began to accept new neighbors during the reign of Sultan Suleiman the Magnificent. The neighborhoods of Uskudar, Tophane, Besiktas and the hills behind them, which can be counted as within the Bosphorus, started to develop during the reign of Fatih Sultan Mehmed and remained limited to their surroundings. The first seaside mansions in the Bosphorus were built on lands given to bostancibashis, but their number did not exceed the fingers of one hand in those years. Moreover, these mansions were not residences occupied throughout the year. The first settlement and development in the Bosphorus began with the construction of a small complex consisting of a mosque, school, fountain, drinking fountain, well, and cemetery by Neslishah Sultan on the western shore of Istinye Stream opposite the bathhouse built by Gazi Ali Pasha. With the popularity of recreational areas, Bosphorus settlements accelerated from the end of the 16th century and the beginning of the 17th century, and the region developed from year to year. Before the settlement in the Bosphorus increased during the reign of Sultan Suleiman the Magnificent, old Bosphorus villages that lived on fishing and agriculture such as Ortakoy, Beylerbeyi, and Cengelkoy were small-scale settlements. The population of these small villages began to increase rapidly from that period onwards. Today, as far as we can learn from historical records, the "Tokat Garden" that Fatih built on Beykoz, the palaces that Sultan II Bayezid built in Besiktas and Beykoz Sultaniye Meadow, and the structures like Hasbahce that Sultan II Murad built in Kandilli were the oldest summer palace settlements in the Bosphorus. According to the information given in the Seyahatname by Evliya Celebi, the Bosphorus mansions and palaces were in a neglected and ruined state due to the permanent wars that began with the Vienna campaign, but the coasts of the Bosphorus will come to life again after this period. The first mass construction in the Bosphorus during this period will take place during the reign of Sultan III Ahmed and Grand Vizier Nevsehirli Damat Ibrahim Pasha. The Bosphorus, which underwent various changes in various periods, was another manifestation of civilization within the city of civilization, Istanbul, in terms of its architecture, transportation vehicles, and lifestyle. The most obvious examples seen within the Bosphorus civilization were the Bosphorus mansions. Until the 1700s, when the calendars showed, Bosphorus settlements were not so widespread, but with the reconstruction of mansions outside Hasbahce, the Bosphorus began to reveal its new architectural identity, and life in the region spread throughout the year.

The lives of the Bosphorus have also influenced Istanbul's prominent figures, particularly since the 1850s. Yalis, hundreds of palaces-like structures, stretch along both sides of the Bosphorus and have now turned into Bosphorus mansion workshops. The 19th century was a brilliant era for the Bosphorus. Foreign architects brought to Istanbul during the Tanzimat period and later years were commissioned to build large and extravagant yalis along the Bosphorus. Some of the famous architects of that era include Italian Fossati, English Smith, French Garnier and Bourgeois, German Bruno Taut, and Zaranko. In the early 1900s, a period of mixed emotions, when the power of the Ottoman dynasty weakened, some people took advantage and built their new mansions in the Bosphorus, marking the beginning of an adventure that continues to this day. Looking at the Bosphorus today, we say "thank goodness for the Hidiv families." The Hidiv Palace (mansion) and its garden in Beykoz, many green areas and architectural heritage, such as Bebek Park and Emirgan Grove, enable us to enjoy the beauty of the Bosphorus today, thanks to them. There are currently 600 registered yalis in the Bosphorus, of which 366 are of historical significance, and 65 are described as "first degree" historic mansions. Abdülhak Şinasi Hisar described the unique world of seaside mansions as "Old grand mansions were like miniature versions of the Ottoman Empire. Here, everyone who worked in the mansion would benefit from the common life. The nanny was Circassian, the sister was black, the servant was Greek, the adopted child was Turkish, the wet nurse was mixed race, the stewardess was from Thrace, the oarsman was Turkish or Greek, the harem guard was Abyssinian, and the gardener was Albanian. These Muslim and Christian elements would gather under this roof to continue their agreement or disagreement within the empire," beautifully capturing the spirit of the era that cannot be described further.

The Christian mansions in the Bosphorus were mostly painted gray, while the mansions belonging to Muslims were painted with lead paint, white, and green. Büyükdere, Tarabya, and Yeniköy were Bosphorus settlements preferred by non-Muslims, next to envoys and dignitaries serving in the Ottoman society. Bebek belonged to government officials, Rumeli Hisarı to scientists, and Kuruçeşme and Ortaköy to members of the dynasty. Beylerbeyi on the Anatolian side was a region preferred by scholars and men of science. In Sarıyer, there were as many mansions, mansions, and villas as the number of mansions. One reason for calling Sarıyer "Paşalar Köyü" was the abundance of mansions, mansions, and villas belonging to pashas. The Istanbul summer residents in the Bosphorus moved to their mansions around May 5th, which changed according to the weather, and stayed here until 40 days before winter began, which was November 12th. Moving to the Bosphorus begins with edicts issued by the sultans, and the return also takes place with this edict. Before moving to the Bosphorus, a kind of residence notification was made to the chief gardener of the region where the residence would be located in the Bosphorus, the law enforcement officers were informed, and a record was kept. Even the seasonal relocation to the Bosphorus was taken very seriously by the administration and law enforcement authorities. Hıdırellez was of great importance to Istanbulites. There was also a protocol for the arrival of state power to the Bosphorus. In the spring months, the sultans passed the kasra in the Golden Horn. Starting with the warming weather, the sultan moved to Beşiktaş Palace. The grand vizier and viziers also moved to their mansions in the Bosphorus. The greatest source of information about the history of the Bosphorus is the Bostancıbaşı Registers. It is possible to reach information about who lived in which mansion and information about the mansion from these registers kept by the Bostancıbaşı. Through what is written, it is also possible to obtain information about many properties such as mosques, masjids, coffee houses, and boat houses. When the sultan of the period went on a Bosphorus tour, the chief gardener would move to the helm of the boat and answer the sultan's questions about which mansion belonged to whom by looking at the register. One interesting feature of the mansions in the Ottoman period was that if the owner of the mansion, pasha, gentleman, or lord, was in exile, the windows and doors of the mansion would be kept closed. There was no vitality in these mansions until the mansion owner was pardoned. The Dolmabahçe Palace, located on the Bosphorus coastline, was built as a palace structure and surrounded the Bosphorus silhouette. Beylerbeyi Palace was a medium-sized state palace and had the nature of a state guesthouse. Besides its architectural diversity and colorfulness, the Bosphorus inspired important works in literature and music history, especially during moonlit nights.

First Applications in History

It is known that since the transition of humanity to settled life, they have started to develop engineering methods in addition to using existing resources for water supply. The first applications based on nature observations are the reservoirs built for water supply in dry periods when the need is high. The discovery of techniques for transporting water from its source to residential areas also dates back to ancient times. It is thought that the water needs of the first settlements and villages were provided from nearby rivers and lakes. Sometimes, digging a well was necessary to reach water sources. The importance of wells in water supply, especially in rural areas, is emphasized in the Solon Laws dated to the 6th century BC. According to this, the right to use common wells is given to those residing within a 4-stage (approximately 740 meters) area, while those living further away are required to dig their own well for their own use.It is known that engineering practices for urban water supply began to be implemented about five thousand years ago in Mohenjo-Daro, an important settlement area of the Indus civilization in Pakistan, and in the Bronze Age settlements in Egypt. During the same period, canal systems, wells, and cisterns were used for water supply in Minos in Crete and later in the Mycenaean civilizations in Greece. Until the Pax Romana, the long period of peace of the Roman Empire, settlement areas built on advantageous high hills were preferred from a defense perspective. In order to meet the water needs of these settlements, deep wells had to be dug, cisterns that would store rainwater had to be found, or practices for transporting spring waters had to be implemented. The well belonging to the Miken Era, which can be descended into by stairs and located on the Athens Acropolis, can be considered a notable example. Another alternative solution, the use of cisterns for collecting rainwater and underground water, is known to have been used in settlement areas in the Near East and Mediterranean since the 3rd millennium BC. The first cisterns were generally pear-shaped reservoirs carved into the main rock, covered with a stone or wooden lid. The interior surfaces of these cisterns were sometimes plastered against leakage. These types of cisterns are encountered in many Hellenistic and Roman period settlements in Anatolia. Research on the water supply of the Hellenistic period in Pergamon showed that these cisterns on the Acropolis could provide water for 20,000 people in the event of a possible siege.While the construction of water channels, cisterns, and wells known from the Archaic and Classical periods in the Aegean geography continued in the Minoan and Mycenaean civilizations, more advanced water supply and drainage systems began to be built from the Hellenistic period onwards. In this regard, the Eupalinos Tunnel in Samos Island is a remarkable example of the Ancient Age.

Water Engineering in the Roman World

During the Roman period, the magnificent water structures built using the developed techniques of vaults and arches played an important role in the overall urban development activities throughout the empire. The Aqua Appia, the first aqueduct of Rome, was built in 312 BC as a water canal, while the Aqua Anio Vetus, from a later period, was constructed as an underground gallery. After the Punic Wars and the elimination of the Carthaginian threat, the Aqua Marcia aqueduct was built, mostly above ground. In addition to collecting spring water, facilities were constructed to collect surface water during the Roman era. The desired amount of water was collected in storage basins and then given to the aqueduct after the solid particles inside were settled. To convey water, various construction methods and materials were used depending on the terrain and technical possibilities of the time, such as galleries covered with stone slabs or vaults, channels and tunnels carved into the rock, and water arches. The galleries were typically built with Horasan mortar and small rubble stones inside wide trenches parallel to the contour lines, and were coated with a waterproof layer for durability.

In the city of Rome, the galleries of the Aqua Marcia aqueduct were constructed using finely cut stones. During the Roman era, a type of concrete called "Opus Caementicium" was also used for constructing aqueducts. The galleries of Roman-era aqueducts in Aix-en-Provence in southern France and Cologne, Germany were constructed using poured concrete techniques, similar to modern applications, in addition to stone masonry. The slope of the water channels was determined based on the topography of the terrain. If the difference in elevation between the starting and ending points of the channel was low, the slope could be kept at a minimum. Roman builders constructed "water arches," which we know as aqueducts, to allow waterways to cross deep valleys and riverbeds. These structures could take the form of a classic arch or a simple wall. Walls could be applied when the gallery level passed a few meters above ground, while monumental water arches with multiple floors could be constructed when the height exceeded four or five meters.

Konstantinopolis, the largest city and administrative center of the Eastern Roman Empire, was built on a peninsula with limited water sources. Initially, the water needs of the city were met by wells and rainwater catchments, but starting from the 2nd century, aqueducts were built to supply water to the city. Historical records show that during the reign of Hadrian (117-138), water was transported to the ancient city of Byzantion from a spring located near Belgrade Forest through galleries.After Istanbul was declared the capital of the empire in the 4th century, new aqueducts were built by Valens (364-378) and Theodosius I (379-395) to meet the growing water demands of the city due to urbanization and population increase. Research projects conducted by Prof. Dr. Kazım Çeçen and later by Prof. Dr. James Crow and his team on the water supply and distribution system of Istanbul during the Byzantine and Ottoman periods, as well as the visual materials and maps they presented, reveal the routes of the aqueducts that supplied water to the city, their entry points through the walls, and their paths within the city. According to the available data, the routes of the aqueducts from both the Byzantine and Ottoman periods show similarities. The water network of both periods relied on water sources at two different levels. The main sources of the high-level aqueducts were Thrace during the Byzantine period and Halkalı, which was also used in the Byzantine period, during the Ottoman period. The low-level aqueducts sourced from the north and south of the Alibeyköy Stream, with the Kirkçeşme aqueduct from the Belgrade Forest, which was utilized since the Byzantine period and improved by Mimar Sinan, being the source in the north.The Bozdoğan Kemeri, thought to have been constructed during the early Byzantine period, was restored during the Ottoman period and continued to serve as a part of Istanbul's water distribution network in the following centuries.In addition to the Ottoman-era records and archaeological data on Istanbul's historical water network, sources from Western travelers should also be taken into consideration, but with caution. For example, French naturalist and traveler Petrus Gyllius, who came to Istanbul to study Byzantine ruins between 1544 and 1550, described the Yerebatan (Basilica) Cistern in detail and stated that it was filled with water from the waterway in winter. He observed that one winter, he saw water flowing into the cistern from a large channel, and the sound of the water did not stop until it reached the middle of the cistern columns. This is a noteworthy observation that the water supply line to the cistern was in use in the 16th century. The work of Andreossy, who served as the French ambassador to Istanbul between 1813 and 1817 and introduced the water structures and aqueducts, also provides information on the intake structures of the Ottoman-era aqueducts, and the north of Kirkçeşme.

Hadrianus Transmission Line

Due to the absence of physical remains of the first water supply system dating back to the 2nd century AD in Istanbul, our knowledge of the system is based on the written sources of the Byzantine period. The route of the line can only be guessed by taking into account the Kirkçeşme water supply line during the Ottoman period. Because of the relationship between both water supply lines, it was claimed that the Mağlova Aqueduct and the water arches in Kemerburgaz were structures belonging to the pre-Ottoman period and that the remnants of the Hadrian water supply system were the result of the repairs made during the Ottoman period. However, this hypothesis is no longer accepted, and it is assumed that the areas where these Ottoman water arches are found were once inhabited by the pioneers of the Roman and Byzantine periods. Studies have shown that the lower section of the Kovuk Arch located southeast of Kemerburgaz belongs to the Early Byzantine period, and the foundations of the Uzun Arch located northwest of Kemerburgaz exhibit the characteristics of Roman period structures. These data suggest that the Hadrian water supply system came from a route that started from Belgrad Forest or Cebeciköy and extended to the sources near Kemerburgaz. Knut Olof Dalman had reservations about whether the Hadrian water supply system used the water sources in Belgrad Forest and proposed the Halkalı region in the northeast, where the closest water source to the city was located, by comparing it with the scale of the İznik line. He also suggested that the Mazul Arch in Mahmutbey, which carried the Halkalı waters to Istanbul, was the last structural remnant of the Roman and Byzantine water supply system in the region. This idea was accepted by researchers such as Semavi Eyice, Cyril Mango, and Kâzım Çeçen. Dalman associated the arch with the restorations of V. Constantine and dated it to the 8th century, while Semavi Eyice suggested that it might have been built in an earlier period. However, recent studies have shown that the Mazul Arch is entirely an Ottoman structure. It is understood from the expression "the large water arch that has been meeting the palace's water needs since the era of Fatih Sultan Mehmed" on the 1584 map, which is the oldest document showing Istanbul's Ottoman-era water network, that the Halkalı waters were transported to the city from 1453 onwards. Based on both structural remains and this important document, it is accepted that the Mazul Arch was also built during the Ottoman period and was designed as part of the waterway that met the needs of the old palace in Beyazıt. It is estimated that the Hadrian water supply system, which is thought to have a similar slope to the Valens water supply line belonging to the later period, entered the city from the land walls located five kilometers west of the Basilica Cistern and about 35 meters high from sea level, and thus, the entry point of the line to the city is estimated to be around Eğrikapı Maksemi located north of the historic peninsula's land walls. This suggests that the Hadrian water supply system was used during the Ottoman period and was in parallel operation with the Kirkçeşme water supply line.

How Much Water Does Istanbul Need?

Several studies have been conducted to answer the question of how much water Istanbul needs, and these studies are generally based on accrual data. As part of the 1999 Master Plan, completed in 1990, it was calculated that the gross water requirement per capita was 238 liters per day, of which 133 liters were domestic, 20 liters were industrial, 15 liters were other, and 70 liters were non-billed uses. When considering the population of that year, the total gross water requirement was determined to be 524 million m3. According to the same study, estimations made for 2010 and 2020 show that the domestic water consumption has increased to 153 liters and 171 liters per person per day, respectively, and the gross water requirement with other uses will be 233 liters and 250 liters per person per day. Due to the increase in population and per capita water consumption, the gross annual water requirement has increased to 1,298 million m3 for the year 2010 and 1,556 million m3 for the year 2020. These projections show that the annual water demand will increase 2.5-3 times from 1990 to 2010 and 2020. Similar approaches suggest that the annual water demand will reach 1,663 million m3 by the year 2025 (IMC, 1999). 

Based on the amount of water consumed, data from TÜİK (Turkish Statistical Institute) reveals that the daily water usage per person was calculated to be 190 liters in 2001 and 2020 (TÜİK, 2020).As part of the ongoing İSKİ Master Plan, the extent to which these figures have changed with changing conditions and the size of Istanbul's water needs until the target year of 2053 has been researched. Calculations were made for the three different population scenarios (Table 1) until the year 2053. When each scenario is evaluated separately, it is revealed that depending on whether Istanbul adapts to low, ideal, or high population growth scenarios, the increasing and eventually reaching a water requirement of approximately 1.1, 1.2, or 1.6 billion m3 per year until 2053. (IMP-OG, 2018). Today, when we look at how much water is used in Istanbul, we can say that approximately 3 million m3 per day and an average of 1.1 billion m3 per year are used. This means that we consume 180-185 liters of water per person per day.

Can Istanbul's increasing water needs be met with the city's current water resources? How much of the current water needs can be met today? Are other sources needed for future predictions mentioned above? Or is it possible to reduce water consumption in some way? In order to answer these questions, it is useful to evaluate the current capacity of water resources in Istanbul. When the distribution in Istanbul is examined, it is seen that 65% of the population is settled in Europe and 35% in the Asian side, while the existing water resources are the exact opposite, with 75% in Asia and 25% in the European side. Therefore, with effective water management, the density of the population can be increased on the Asian side where the water resources are more abundant, and water can be transported to the European side as needed.

If we were to ask "Where does Istanbul's water come from?", the answer would be largely from dams and regulators. In addition to surface waters, there are many wells used for drinking, irrigation, and industrial purposes in Istanbul. However, groundwater accounts for only 9% of the water that can be obtained from surface sources, even if all of it is used. In order to meet future water needs, it is possible to greatly increase the storage capacities of the dams in the current water source situation with new dams planned to be built at the basin of the dams. However, the water yields are greatly affected when the dams are operated singly (individually) or integrated. In other words, building multiple dams on the same water source increases the total amount of water that can be taken, and the sum of the added dam capacities is 1,424 million m3 per year. In these total conditions, there is a share of Istanbul's water resources within individual w because the Melen Dam has not yet been completed, and this share is 634 million m3 per year. If the Melen Dam is operated as a regulator, it has been calculated that its individual contribution will be 958 million m3 per year. This amount alone is higher than the total storage capacity of the dams in Istanbul. 

When the dam is built, the regulator will be out of operation, and the individual efficiency will rise to 1,748 million m3 per year. This amount is sufficient to meet the high increase scenario of water needs projected for 2053 (IMP-OG, 2018).The construction of the Melen Dam will significantly alleviate the water stress it experiences during drought periods in the basin flow, with monthly and annual regulation, and prevent Istanbul from becoming dry. However, in the short term, the probability of building this dam is seen as low, so future predictions should not be based on the Melen Dam, at least in the short and medium term. Potential water sources are being investigated in the ongoing Master Plan study, and new plans that can meet the increasing water needs in the future are being proposed. In summary, almost all of Istanbul's water needs are met by surface sources, and the water sources used extend to Kırklareli in the western region and Düzce in the eastern region. 

The main cause of Istanbul's water problem lies in the water holding capacities of the existing dams and lakes, which are approximately 900 million m3. This capacity is only equivalent to Istanbul's annual water needs today. This limitation, which means that all accumulated waters in the dams and lakes are distributed within the same year, leaves the solution to Melen in periods of scarce rainfall. Indeed, Melen meets almost 40-50% of Istanbul's water needs. The most significant disadvantage of the unfinished Melen Dam is the additional burden it puts on the energy budget beyond the contribution it cannot provide to the water budget. Water is pumped from the 18.6 m elevation, which is the regulator level, to the water lines by pressing down to the 210 m elevation...

How is the Drinking Water Treatment Scheme?

Designing an effective water treatment plant is a complex process due to the various unwanted components that can be found in the water source. Even "clean" water can contain some components that need to be "eliminated". The specific components in the water, their relative concentrations, and other water quality parameters that affect treatment are largely dependent on local geology, climate, and human activity conditions. Therefore, treatment processes should be applied based on the characteristics of each water source.In Istanbul, drinking and potable water is provided to the city through 16 different water treatment facilities of varying capacities that treat waters from different sources. 

The total operational capacity of the facilities is approximately 4 million m3/day. Conventional treatment processes, including aeration, chemical treatment, rapid sand filtration, and disinfection, which are commonly used in the treatment of surface waters, are applied in all facilities.With the contamination of water sources and the diversification of parameters that determine water quality, treatment systems are equipped with additional treatment units, with the aim of removing specific parameters. Depending on the characteristics of the water source, ozonation and powdered activated carbon units have been added to facilities with color, taste, and odor problems. The sludge generated by removing solid matter during the treatment process is passed through the concentration and dewatering stages.

Water treatment facilities in Istanbul are managed with an integrated operating system that allows for different water sources to be fed into each facility. The waters of multiple sources can be treated to drinking and potable water quality at each facility.The Cumhuriyet Water Treatment Plant purifies the raw water from Ömerli and Melen, and the majority of it is transferred to the Suatlı Water Treatment Plant, which is connected to the Bosphorus via an underwater tunnel. In the European side of the city, the raw water from the Terkos-Sazlıdere basin is treated at the İkitelli Water Treatment Plant, while the water from Terkos is heated at the Taşoluk Water Treatment Plant. The Büyükçekmece Water Treatment Plant uses its own reserves, while the Ihsaniye, Danamandıra, and Treatment Plant facilities purify groundwater from wells to supply the system. The Cumhuriyet and Ömerli Water Treatment Plants are the largest facilities that supply approximately 60% of the water to the city.Istanbul's water treatment facilities meet the drinking and potable water quality criteria required by regulations. 

However, the taste and odor of tap water are the most complained about issues by consumers. Due to the psychological pressure created by the taste and odor, consumers do not trust tap water and meet their drinking water needs by purchasing bottled water. Accordingly, in water treatment facilities that purify water sources with intense taste and odor, it would be appropriate to use advanced treatment applications such as ozone, biological activated carbon, ultrafiltration, and nanofiltration units in addition to conventional treatment processes.

Where does the water we use go and what happens to it?

After discussing so much about drinking and usage water, we should not forget that these waters eventually need to be disposed of as wastewater. The wastewater generated in Istanbul is treated in different capacities and treatment systems, and then discharged into the sea sometimes directly and sometimes through streams. The level of treatment is determined based on the type of pollutant parameters that need to be removed, depending on the characteristics of the receiving environment, and requires the adoption of the most appropriate technology. 81% of the wastewater discharged into the Marmara Sea, along with organic matter, nitrogen, and phosphorus parameters, are treated in advanced biological treatment facilities (Çanta, Silivri, Selimpaşa, Büyükçekmece, Ambarlı, Ataköy, Tuzla). In all treatment facilities except Ambarlı and Ataköy, which discharge into the Marmara Sea through streams, deep-sea discharge is applied to ensure compliance with swimming water criteria after treatment. Only physical treatment (grids and sand traps) is applied in the Küçükçekmece facility, which accounts for 18% of the discharges into the Marmara Sea. Biological treatment facilities that only aim to remove organic matter account for a small percentage (0.5%).