The Yeşilırmak, which divides Amasya in two as it flows between a pair of rocky slopes, is one of the great rivers of northern Anatolia that drain into the Black Sea, and in antiquity it was known as the Iris. Reaching the sea in the Çarşamba district of Samsun at the end of a course of some 519 kilometres, the river gathers the waters of a wide basin covering roughly five per cent of Turkey's surface area. Its name is said to derive from its placid appearance in summer, when its waters seem to merge with the green of the valley; beneath that calm surface, however, lies a flow regime of great seasonal fluctuation, one that in some years overflows its bed in flood and in others shrinks by late summer to little more than a stream. The river's course from source to sea, the waters brought by its tributaries, the behaviour of its discharge through the year, the alluvium it carries and the dams built across it in the twentieth century together make up the hydrological identity of the river that shaped the Amasya valley.

The Name and the Iris in Ancient Sources

The earliest known name of the Yeşilırmak appears in Hittite texts. Roger Matthews and Claudia Glatz, in their study of the historical geography of north-central Anatolia in the Hittite period, accept that the river was called Kumeşmaha in Hittite sources. In Greek sources it bears the name Iris, under which it appears in the coastal description of Menippus of Pergamon in the first century BC. From Dionysius Periegetes onwards, some ancient authors confused the Iris with the Thermodon (the modern Terme Çayı), a much smaller and clearer stream that reaches the sea at the other end of the Çarşamba Plain.

The ancient author who describes the river's course in the greatest detail is Strabo, the geographer from Amasya. In the twelfth book of the Geographica he writes that the Iris has its sources in Pontus itself, that it flows westward through the middle of Comana Pontica and through the fertile plain of Dazimonitis (today's Kazova), and that it turns north past Gaziura, an old royal seat (most probably Turhal). According to Strabo, the river then bends back towards the east after receiving the waters of the Scylax (the Çekerek) and other streams, flows past the very wall of Amaseia, which he calls "my fatherland", and enters the plain of Phanaroea; there the Lycus (the Kelkit), coming from Armenia, joins it, and the united river, still called the Iris, crosses the plain of Themiscyra and flows into the sea. Strabo also records that this plain was always moist and grassy, able to support herds of cattle and horses alike, suited to the sowing of millet and sorghum in almost unlimited quantities, and so well watered that drought never brought famine to its people. Written two thousand years ago, these lines correspond remarkably closely to the main outlines of present-day hydrography.

Source, Tributaries and Basin

The Yeşilırmak rises on the slopes of the Köse Mountains south-west of the Suşehri district of Sivas; the elevation of its source area is given in some sources as 2,800 metres. The main branch, collecting the surrounding springs and brooks, first flows under the name Tozanlı Suyu, enters the Almus reservoir near the Almus district of Tokat, and then, as the Tokat River, crosses the plains of Tokat and Turhal. Beyond Turhal the river passes through the Çengel Gorge, turns north from the Geldingen Plain onwards, cuts through the Canik Mountains between the Topuzlu and Eğrikazık ranges and opens onto the Çarşamba Plain, where it builds a broad delta before reaching the sea. Its mouth is named in some official texts as Civa Burnu and in others as Çatlı Burnu.

What makes the river a great one is its tributaries, each of them a significant watercourse in its own right. The largest is the Kelkit. Formed by the union of streams descending from the high mountains north-west of Erzincan and from the Çimen Mountains in Gümüşhane, the Kelkit flows from east to west past Kelkit, Suşehri, Koyulhisar, Reşadiye, Niksar and Erbaa, and joins the Yeşilırmak on the border between Amasya and Tokat, between Taşova and Erbaa. The Çekerek rises in the Yıldız Mountains north-west of Sivas, receives the Çorum Çayı from the west, and meets the main branch at Kayabaşı, about 15 kilometres south of Amasya. The third major tributary is the Tersakan. It rises on the slopes of Akdağ, takes in the overflow of Lake Ladik, passes through the Havza district and Suluova, and enters the Yeşilırmak north of Amasya. Its course, which runs first west, then south, then east, gave the stream its name Tersakan, "the one that flows backwards". The Şeyhsuyu, Gümüşsuyu, Derinöz and Salhan are its principal feeders.

The dimensions of these tributaries vary from source to source, and the figures must be compared with care. The length of the Kelkit is given as 320 kilometres in some studies, 356 in others, and 400 in official basin documents; for the Çekerek both 200 and 256 kilometres circulate, and for the Tersakan both 91.4 and 100 kilometres. The same is true of the main river: while almost all Turkish sources take 519 kilometres as the standard, some foreign reference works give a shorter figure of 418 kilometres. Most of the difference depends on which spring is taken as the head of the main branch and on how the length of a bed altered by reservoirs is measured.

For the size of the basin, too, figures close to one another but not identical are in use. Local institutional descriptions give 36,114 or 36,144 square kilometres, academic studies 38,730 square kilometres, and the flood management plan a precipitation area of 39,626 square kilometres. Whichever value is taken, the basin, one of Turkey's 25 river basins, covers close to five per cent of the country's area. It extends into the territory of eleven provinces: Tokat, Samsun, Amasya, Çorum, Yozgat, Sivas, Gümüşhane, Giresun, Erzincan, Ordu and Bayburt. All of Tokat lies within the basin; about 86 per cent of Amasya drains to the Yeşilırmak, while a small area around Gümüşhacıköy drains to the Kızılırmak. At its narrowest, near Koyulhisar, the basin is 30.5 kilometres wide; at its widest, between Ladik and Zile and Akdeğirmen, it reaches 170 kilometres. The Kazova, Geldingen, Taşova and Çarşamba plains are the principal lowlands strung along the main bed, and the lakes of Ladik, Borabay and Kaz also lie within the basin.

The River and Its Tributaries in the Amasya Section

The Yeşilırmak runs for 129 kilometres within the boundaries of Amasya province. The river enters the province from the south and, after receiving the Çekerek at Kayabaşı, heads for the city through a narrow gorge. This approach is called the Ferhatarası Valley, some 10 kilometres long, running from the village of Kayabaşı to Hacılar Meydanı in Amasya. Below the city come the 8.5-kilometre Beşgöz Valley between Boğazköy and the mouth of the Tersakan, the 20-kilometre Onlukköprü Valley running from the Tersakan's mouth through Ziyaret and Yenice to the village of Kuzgeçe, and the 18-kilometre Durucasu Valley from Kuzgeçe to the village of Çambükü in Taşova. From here the river emerges onto the Taşova lowland and meets the Kelkit. Further upstream, the Karaçavuş Valley, which runs for 39 kilometres from the mouth of the Kuruçay to the mouth of the Deliçay, is a narrow passage squeezed between Sarıtaş Dağı and Buzlu Dağ and contains the Şahin Kayası Canyon.

The regime of the smaller streams that join the main branch within the province plays an important part in the sudden rises of the Yeşilırmak. The 48-kilometre Deliçay, which rises on the Buğalı uplands of Sakarat Dağı, can fall to half a cubic metre per second, while its highest recorded discharge has reached 212 cubic metres per second. The discharge of the 35-kilometre Destek Çayı, which flows between Karaömer Dağı and the Canik Mountains and joins the river at Taşova, likewise ranges between 0.5 and 130 cubic metres per second. The 50-kilometre Kuruçay, which follows the Amasya-Tokat boundary, and the 40-kilometre Gökdere Çayı in Taşova, descending from the Canik Mountains, are among the other streams feeding the main branch. These streams almost dry up in summer; in spring downpours, however, they can swell enough to overflow their beds within a few hours. The lowest point in the province, 160 metres above sea level, lies near the village of Umutlu in Taşova, where the Hasan Uğurlu reservoir begins.

Geological Development

The most striking feature of the Yeşilırmak is that it cuts straight across the Black Sea Mountains. According to a study published in 2015 by Nizamettin Kazancı, Esra Gürbüz and Alper Gürbüz, the main branch and its tributaries flow east to west in their upper and middle courses, following active fault lines. While the tributaries begin at elevations of between 1,600 and 2,050 metres, the bed falls to 190 metres in the middle course near Erbaa. The researchers note that all the tributaries, the Kelkit above all, flow in a "saw pattern" in their upper courses, cutting the floors of their narrow, deep valleys almost like a saw and gathering nearly all of their sediment load from these sections. Where the gradient eases, in the plains, the streams flow in a "pan pattern" and leave a large part of their bedload behind.

Pan-type lowlands such as Suşehri, Turhal, Pazar, Niksar, Taşova, Erbaa, Amasya and Suluova are, tectonically speaking, depressions. Core logs from boreholes drilled in these areas by the State Hydraulic Works (DSİ) have shown lake deposits of Pliocene-Quaternary age, 50 to 200 metres thick, made up of claystone, marl, sandstone and mudstone. In the developmental model proposed by Kazancı and his colleagues, fluvial erosion on the slopes of the Black Sea Mountains facing inner Anatolia was established at the beginning of the Late Miocene, and the mountains began to wear down at an average rate of 0.4 to 1.2 millimetres a year even as they rose. At that time the Çekerek and the Yeşilırmak drained into an "Amasya Lake", the Tersakan into a Suluova Lake and the Kelkit into a Taşova-Erbaa Lake. Deepened by the North Anatolian Fault, these lakes were filled with thick deltaic deposits. In the Middle Pleistocene, when the mountains' weak volcanic bedrock was deeply incised, north-flowing streams captured the waters of the inland lakes; the lakes drained and the present drainage network emerged. According to the researchers, the present arrangement of the Yeşilırmak and the Çarşamba delta took shape within the last seven thousand years.

Discharge and Flow Regime

The mean annual discharge of the Yeşilırmak in the Amasya section is about 121 cubic metres per second, and on average 5,707 million cubic metres of water pass through this section each year. This average does not fully reflect the river's true character. The highest discharge ever measured at Amasya is 1,914 cubic metres per second and the lowest just 1.83 cubic metres per second, a difference of more than a thousandfold between the river at its fullest and at its feeblest. Floods occur mostly in March, April and May. In this season, when snowmelt combines with spring rain, the river fills its bed; in late summer and autumn the water level drops markedly. This is why it is classed as a river of irregular regime.

The contribution of the tributaries is essential to understanding this picture. The Çekerek has a mean discharge of 20 cubic metres per second and an annual flow of 842 million cubic metres; its highest measured discharge has reached 362 cubic metres per second and its lowest has fallen to 0.09. The Tersakan's mean discharge stays at a modest 3.96 cubic metres per second, yet in downpours it can swell to 317; its lowest discharge is 0.021 cubic metres per second. This stream floods not only in spring but also during summer storms. The Kelkit, with a mean discharge exceeding 70 cubic metres per second and an annual flow of up to 2,526 million cubic metres, is the most powerful tributary, joining the main branch below Amasya; its highest discharge has been measured at 905 cubic metres per second. The Kelkit carries most water in April and least in October, and has a complex regime fed by both rain and snow.

Monthly figures for 1995-2015 from the gauging station at Çarşamba, near the river's mouth, show the seasonal course of the regime clearly. According to the study by Elif Sürücü and Yasin Demir based on these data, the mean flow stands at around 165 cubic metres per second in January and 153 in February, rises to 244 in March and 290 in April, and peaks in May at 376.4 cubic metres per second. Falling rapidly from June onwards, the flow drops to 74.51 cubic metres per second in July, a reduction of about 80 per cent between May and July. Running at between 75 and 100 cubic metres per second in August, September and October, the flow recovers in November with the autumn rains. Over the same period the station's annual mean was calculated at 170.78 cubic metres per second, while the mean for a single May rose as high as 1,176 cubic metres per second. This monthly distribution shows how decisive the spring rise is for the river.

Dry Years and the Decline in Discharge

Long-term measurements point to a marked decline in the flow of the Yeşilırmak over the past forty years. Kadri Yürekli examined the monthly data for 1984-2002 from the Durucasu station between Amasya and Taşova and found that at this point, which drains an area of some 21,650 square kilometres, flow decreased in a statistically significant way in nine months of the year, all except April, May and June. That the river carries less water for the rest of the year while the spring rise persists indicates that the basin's supply outside the snowmelt season has weakened.

According to thirty years of measurements by the Samsun regional directorate of the State Hydraulic Works, the long-term mean discharge of the Yeşilırmak where it reaches the sea is 149 cubic metres per second. In the period 2014-2023 the river exceeded this mean only in 2016, at 165 cubic metres per second, and in 2018, at 164, and flowed exactly at the mean in 2015. In the other years discharge stayed below the mean, measuring 64 cubic metres per second in 2014, 104 in 2017, 125 in 2019, 133 in 2020, 85 in 2021, 129 in 2022 and 136 in 2023. In the first nine months of 2024 the mean remained at 94.1 cubic metres per second. It is striking that precipitation in the basin fell by only about one per cent over the same decade. The geographer Muhammet Bahadır of Ondokuz Mayıs University and the State Hydraulic Works' observation engineers in the region attribute the decline less to rainfall than to the basin's growing population and its use of water for irrigation and drinking. Instantaneous water levels are recorded at 92 points on the main river and its tributaries across the basin.

Floods

The most visible consequence of the irregular regime is flooding. Archival documents and newspaper reports from the early decades of the Republic show that Amasya and its surroundings suffered floods and inundations again and again between 1930 and 1960. In this period the Tersakan, Çekerek, Deliçay and Kelkit, which join the Yeşilırmak within the province, also overflowed their beds from time to time alongside the main river, and in some years several streams flooded at once. Almost every year at the start of spring, waters swollen by melting snow and rain destroyed houses, turned orchards and fields into marshes for long periods and ruined the crops. Malaria spread on land left under water for weeks, road links were cut, and the railway line and stations were damaged, bringing transport to a halt.

Turgut İleri's study of the period 1931-1941 documents that floods struck Amasya almost every year in that decade and that the major floods, setting aside smaller inundations, caused the collapse of houses, heavy damage to cultivated land and loss of life. Meetings were held with the Red Crescent under the chairmanship of the governor, and aid was sent to the victims. Another study, which examines the period 1930-1960 through the national press, states that the floods it covers caused no loss of life and that the damage was concentrated on homes, workplaces and farmland; since the two studies cover different events and draw on different sources, this distinction should be kept in mind. That flood prevention is among the purposes of the Almus Dam in the upper basin and of the Süreyyabey Dam on the Çekerek is a direct consequence of this historical experience.

Alluvium, Sediment and the Delta

The Yeşilırmak spreads the fine material it strips from the mountains across valley floors and plains. Built up over centuries, this alluvium formed the dark, fertile soils of the valley between Amasya and Taşova. Combined with the microclimate that prevails in the valley, these soils are the basis of fruit and vegetable growing; the Onlukköprü Valley, where the misket apple that made Amasya famous is grown, also lies on the river's alluvial floor. Local produce such as the flower okra (çiçek bamyası) grows in the same riverside gardens. The yellowish, turbid look of the river for much of the year comes from its suspended load.

The sediment load of the basin is very high by Turkish standards. The Kelkit is ranked first in the country for the amount of solid material it carries per unit area, a value calculated at 692 tonnes per square kilometre per year. This material, torn from the narrow valleys of the upper courses, is the direct product of the saw pattern described above. For dams the price is heavy; the economic life of a reservoir is determined by the amount of sediment arriving from its catchment, and reservoirs on so heavily laden a river are bound to fill up over time.

The final resting place of the river's alluvium is the Çarşamba Plain. Counted among the largest deltas of the Black Sea, the plain consists of older alluvium in the south, standing 60-70 metres above sea level, and younger alluvium in the north. Since the detailed study by Hamit İnandık published in 1957, the delta has been described as the work of a river that frequently shifted its bed during the Quaternary. İsmail Atalay attributes the delta's growth on this scale to the large quantity of solid material carried by the river, the shallowness of the sea off the coast and the weakness of the currents. Marshes, lagoons and abandoned meander loops show that this development continued until recently.

The dams have upset this balance. Because the sediment that accumulates in the reservoirs on the river, above all those of the Hasan Uğurlu and Suat Uğurlu dams, can no longer reach the coast, the delta has stopped advancing seaward and has begun to retreat under the action of the waves. A study by Derya Öztürk and Sibel Uzun based on satellite images from 1985-2022 showed that erosion affected 61 per cent of the shoreline along some 18.5 kilometres of the delta's coast. The rate of erosion reached 25.8 metres a year in the section west of the river mouth and 7.7 metres a year to the east; in thirty-seven years a total of 261.45 hectares of land was lost to the sea, 179.23 in the west and 82.22 in the east. Some researchers point out that the absence of the fresh silt that once spread over the plain every spring has also weakened the replenishment of the farmland.

Water Quality

The water of the Yeşilırmak is slightly alkaline. In monthly measurements at the Çarşamba station between 1995 and 2015 the mean pH was 8.10, with small differences between months ranging from 8.02 to 8.16. Electrical conductivity, an indicator of the water's salt content, averages around 464 microsiemens; the highest values are measured in February and the lowest in April. The reason for this difference is dilution. As discharge increases, the dissolved salts in the water decrease, and the same study found a significant inverse relationship between discharge and conductivity, sodium, calcium and magnesium, bicarbonate and sulphate. At the same station discharge showed a rising trend only in January, with no marked change in the other months; the researchers suggest that seasonal rainfall and the dams upstream of the station may play a part in this.

At the Durucasu station, by contrast, the period 1984-2002 saw a decline in flow accompanied by a rise in pH in eight months, in chloride in January and June, and in sulphate and the sodium adsorption ratio in January. Kadri Yürekli attributes this change to the growth of industrial and urban areas in the basin, to livestock waste left untreated, to the excessive use of mineral fertilisers and to soil degradation. The Tersakan is known to be class one for alkalinity and class two for salinity as irrigation water; the pollution load it gathers from the Suluova and Merzifon plains enters the main branch just below Amasya.

Dams and Hydroelectric Power Plants

In the second half of the twentieth century the Yeşilırmak was regulated by a series of dams and power plants for flood control, irrigation and energy production. The first major link in this chain is the Almus Dam, built in 1964-1966 on the main branch 35 kilometres east of Tokat. Its earth-fill body rises 78 metres above the riverbed; at normal water level the dam holds 950 million cubic metres and forms a lake of 31.30 square kilometres. It irrigates 21,350 hectares, and its 27-megawatt plant generates 99 gigawatt-hours of electricity a year. Immediately below Almus lies the smaller Ataköy Dam.

The two large dams on the stretch of the river near the sea are the centre of gravity of the basin's energy production. The Hasan Uğurlu Dam, built in 1971-1981 in the Ayvacık district of Samsun, rises 175 metres above the bed with its clay-core rockfill body. Its reservoir of 1,073 million cubic metres covers 22.66 square kilometres, and its 500-megawatt plant generates about 1,217 gigawatt-hours a year. Built with credits from the Japanese government, the dam carries water to its turbines through a tunnel cut into the adjacent mountain rather than through penstocks. It was named after Hasan Uğurlu, the State Hydraulic Works' Samsun regional director, who was killed in a traffic accident in 1971, at the start of construction. The name of his wife, Suat Uğurlu, who died in the same accident, was given to the second dam, built in 1975-1982 18 kilometres downstream. Rising 51 metres above the bed, the Suat Uğurlu Dam holds 182 million cubic metres and supplies irrigation water to 83,312 hectares of the Çarşamba Plain; the installed capacity of its plant is given in some sources as 46 megawatts and in others as 69.

There are large structures on the tributaries as well. The Kılıçkaya Dam on the Kelkit, opened in 1989, is with its 120 megawatts the largest plant on that tributary; the ten plants on the Kelkit have a combined capacity of 570 megawatts. The Süreyyabey Dam, also known as the Çekerek Dam, built in 1996-2004 on the Çekerek within Yozgat province, stores 1,310 million cubic metres behind a rockfill body rising 103 metres above the bed, irrigates 66,165 hectares and produces 51 gigawatt-hours of energy a year. Among its purposes are protecting Amasya from Çekerek floods and solving the irrigation problem of the Geldingen Plain, where water becomes very scarce in summer. On the tributaries in Amasya there are smaller irrigation dams, such as Yedikır (1979-1986), Derinöz (2003) and Gümüşhacıköy (1991) in the Tersakan basin, Gediksaray (1994) in Göynücek and Destek (2001) in Taşova.

In the Amasya section the river's gradient suits run-of-river plants better than large reservoirs. The Çarıklı and Amasya Kale plants in the central district, the Midilli plant between the central district and Taşova, and the Umutlu, Yavuz and Yenidereköy plants in Taşova are of this type. According to some compilations there are 19 dams and hydroelectric plants on the main river with a combined installed capacity of 904 megawatts, generating on average some 2,300 gigawatt-hours a year. A lasting effect of the reservoirs is that they soften the river's flow regime; part of the spring rise is held back in the reservoirs and released in a controlled way during the summer months.

Basin Management and Planning

Today the water resources of the Yeşilırmak are managed through plans prepared at basin scale. The contract for the Yeşilırmak Basin Flood Management Plan, prepared in line with the European Union's Directive 2007/60/EC on the assessment and management of flood risks, was signed on 27 September 2013, and the plan was completed in 2015. Under the plan a preliminary flood risk assessment of the basin was carried out, flood hazard and risk maps were prepared, areas at risk were studied with two-dimensional hydrodynamic models, and recommendations were made on the measurement network needed for early warning systems. According to the plan, the basin's mean annual precipitation is 528 millimetres, its mean annual runoff 6.10 cubic kilometres and its mean basin yield 5.1 litres per second per square kilometre.

The measures set out in the plan have been tracked since 2017 through the ministry's monitoring system and since 2020 through the National Water Information System. Work on updating the flood management plan began in 2021, the same year in which the Yeşilırmak River Basin Management Plan was completed. In addition, a drought management plan and a sectoral water allocation plan have been prepared for the basin, and a project examining the effects of climate change on its water resources has been carried out. At a time when discharge is falling although rainfall has hardly changed, the common concern of these plans is how limited water is to be shared among irrigation, drinking water, energy and the natural environment.

Chronology

1st century BC: Menippus of Pergamon mentions the river under the name Iris in his coastal description.

Late 1st century BC - early 1st century AD: In the Geographica, Strabo describes the course of the Iris from Comana to the sea and its tributaries the Scylax and the Lycus.

1930-1960: Amasya and its surroundings are repeatedly struck by floods of the Yeşilırmak and its tributaries; between 1931 and 1941 floods occur almost every year.

1957: Hamit İnandık publishes his detailed study of the Yeşilırmak delta (the Çarşamba Plain).

1964-1966: The Almus Dam is built on the main branch.

1971: Construction of the Hasan Uğurlu Dam begins; Hasan and Suat Uğurlu are killed in a traffic accident.

1975-1982: The Suat Uğurlu Dam is built.

1979-1986: The Yedikır Dam in the Tersakan basin is built and put into service.

1981: The Hasan Uğurlu Dam and power plant are completed.

1984-2002: Measurement period at the Durucasu station in which a significant decline in flow is observed in nine months of the year.

1985-2022: A total of 261.45 hectares of coastal land in the Yeşilırmak delta is lost to erosion.

1989: The Kılıçkaya Dam on the Kelkit is put into service.

1996-2004: The Süreyyabey Dam is built on the Çekerek.

2013: The contract for the Yeşilırmak Basin Flood Management Plan is signed (27 September).

2015: The Flood Management Plan is completed; the study by Kazancı, Gürbüz and Gürbüz on the geological development of the Yeşilırmak is published.

2021: The River Basin Management Plan is completed and work begins on updating the flood management plan.

2014-2023: In seven years out of ten, the mean annual discharge where the river reaches the sea stays below the long-term mean of 149 cubic metres per second.

Bibliography

Primary sources

  • Strabo, Geography XII.3.15 (translated by H. L. Jones, Loeb, 1924).

Academic studies

  • Sürücü, Elif; Demir, Yasin. "Yeşilırmak Nehrinde Bazı Sulama Suyu Kalite Parametrelerinin Eğilim Analizi ve Değerlendirilmesi". Türk Tarım ve Doğa Bilimleri Dergisi 11(4), 2024, pp. 992-1000.
  • Yürekli, Kadri. "Variability Analysis on Water Quality of Streamflow from Yesilirmak Basin in Turkey". Gaziosmanpaşa Üniversitesi Ziraat Fakültesi Dergisi 34(1), 2017, pp. 33-37.
  • Öztürk, Derya; Uzun, Sibel. "Yeşilırmak Deltası'nda Kıyı Erozyonunun Doğrusal Regresyon Oranı Yöntemiyle Analizi". Uludağ Üniversitesi Mühendislik Fakültesi Dergisi 28(3), 2023, pp. 847-866.
  • Matthews, Roger; Glatz, Claudia. "The Historical Geography of North-Central Anatolia in the Hittite Period". Anatolian Studies 59, 2009, pp. 51-72.

Official sources

  • Governorship of Amasya, "Yeryüzü Şekilleri" (general state of the Yeşilırmak basin, rivers, valleys, dams): https://amasya.gov.tr/yeryuzu-sekilleri
  • Ministry of Forestry and Water Affairs, General Directorate of Water Management, Yeşilırmak Havzası Taşkın Yönetim Planı, Yönetici Özeti, 2015.
  • Ministry of Agriculture and Forestry, General Directorate of Water Management, Yeşilırmak Havzası (basin introduction document).

Books

  • Kazancı, Nizamettin; Gürbüz, Esra; Gürbüz, Alper. "Yeşilırmak'ın Jeolojik Olarak Doğuşu ve Gelişmesi, Kuzey Anadolu, Türkiye". Abstracts of the 68th Geological Congress of Turkey, Ankara, 2015, pp. 140-141.
  • İleri, Turgut. "Amasya'da Meydana Gelen Sel Baskınları (1931-1941)". Kesit Akademi, 2024. amasya.gov.tr

Other sources

  • "Amasya'da Sel ve Su Taşkınlarının Ulusal Basındaki Yansımaları (1930-1960)". Ondokuz Mayıs University Open Access.
  • Anadolu Agency, "Kızılırmak ve Yeşilırmak'ta debi son 10 yılın 7'sinde ortalamanın altında kaldı", 2024.
  • Dam data based on State Hydraulic Works (DSİ) figures: the Almus, Hasan Uğurlu, Suat Uğurlu and Süreyyabey dams.
  • Enerji Atlası, "Yeşilırmak" (list of dams and hydroelectric plants): https://www.enerjiatlasi.com/akarsular/yesilirmak.html
  • Wikipedia, articles "Yeşilırmak", "Kelkit Çayı", "Tersakan Çayı" and "Yeşilırmak Deltası" (supplementary source).

Online sources