Tigris & Euphrates Basin

The Tigris

The Tigris river also has its springs in the highlands of Eastern Turkey, but the main contribution to the river comes from the tributaries in Iraq. The Tigris river follows a southeastern route in Turkey to the city of Cizre, where it forms the border between Turkey and Syria for 32 km before entering Iraq. It joins the Euphrates in Qurna and continues its journey as the Shatt al-Arab to the Persian Gulf.

The Tigris is the second longest river in Southwest Asia, 1,840 km long. The city of Baghdad is located on the conjunction of the Tigris and Diyala rivers and navigation is possible from Baghdad downstream. Because of the irregularities of the tributaries' flows, the Tigris is widely known for its infamous floods. In the southern part of Iraq, immense areas are regularly inundated, levees often collapse, and villages and roads must be built on high embankments.

The Tharthar reservoir was planned in the 1950s to protect Baghdad from the ravages of the periodic flooding of the Tigris by storing extra water discharge upstream of the Samarra barrage. A derivation canal that links the Tigris to the Euphrates through the Tharthar Valley has already been realized and operative since 1988. Thus both rivers are connected with each other far before Shatt-el-Arab.

The Euphrates
The Euphrates river has its springs in the highlands of Eastern Turkey and its mouth at the Persian Gulf. It is the longest river in Southwestern Asia with 2,700 km, and its actual annual volume is 35.6 billion cubic meters. The Euphrates river is formed in Turkey by two major tributaries; the Murat and the Karasu. These two streams join together and form the Euphrates river and the the Keban Dam Lake.

Euphrates follows a southeastern route to enter Syria at Karkamýs point. After entering Syria, the Euphrates continues its southeastern course and is joined by two more tributaries, the Khabur and the Balikh. Both of these tributaries have their sources in Turkey and they are the last bodies of water that contribute to the river. After entering Iraq, the river reaches the city of Hit, where it is only 53 m above sea level. From Hit to the delta in the Persian Gulf, for 735 km, the river loses a major portion of its waters to irrigation canals and to Lake Hammar.

The remainder joins the Tigris river near the city of Qurna, and the combined rivers are called the Shatt al-Arab.

Background
Understanding the hydrology of the Tigris & Euphrates Basin is crucial to understanding the effects water management projects have on the rivers. The topography is such that all the highland regions are located in the north and eastern parts of the basin in Turkey, Iraq, and Iran. These mountains reach heights of almost 3,500 meters to the south, and of around 4,500 meters un the upper part of the Euphrates region. In the Tigris basin, heights of up to 4,200 meters are recorded in southeast Turkey.

It is in the these highlands that almost all of the flows of the two rivers are generated as annual precipitation totals commonly exceeding 1,0000 mm. Precipitation in the basin is largely confined to the winter months from October through April. This means that a large proportion of the total falls as snow on the uplands and consequently the water is locked in the solid state on the mountain slopes until temperatures begin to rise in spring and early summer.

Çubuk I Dam

Southeastern Anatolia Project,
otherwise known as GAP

Although Turkey controls the headwaters of the Tigris and Euphrates rivers, 40% of its arable land is in southeastern Anatolia, which suffers from a general shortage of water. To alleviate this shortage, Turkey initiated the South Eastern Anatolia Development Project, also known by its Turkish acronym GAP. It is the biggest and the most comprehensive project ever implemented in Turkey, and one of the biggest of its kind in the world. GAP covers in addition to the irrigation and hydropower schemes, all the related social and economic sectors including industry, transportation, mining, telecommunications, health, education, tourism, and infrastructure.

The initiative includes 13 major projects which are promote irrigation and hydropower generation. The project encompasses the construction of 22 dams and 19 hydroelectric power plants on the Euphrates and Tigris Rivers and their tributaries. It is planned that at full development, over 1.7 million hectares of land will be irrigated and 27 billion kilowatt hours of electricity will be generated annually with an installed capacity over 7,500 million watts. The area to be irrigated accounts for 19% of the economically irrigable area in Turkey (8.5 million hectares), and the annual electricity generation accounts for 22 % of the country's economically viable hydropower potential (118 billion kilowatt hours).

On the Euphrates, 3 dams are in operation (Keban, Karakaya and Atatürk), while 4 still remain under construction. Most of the projects on the Tigris River are either under construction or still in the planning phases. The water of the Euphrates River is regulated by means of large reservoirs of the Keban and Atatürk Dams. However, the waters released from the hydroelectric power plants (HEPP) of those dams also need to be regulated. During the periods of low demand for power, only one of 8 units of the HEPP of the Atatürk Dam will be in operation while during the periods of high demand, all the 8 units will be in operation. Hence, the amount of water to be released from the HEPP might vary between 200 cubic meters per second and 2,000 cubic meters per second in one day depending upon the energy demand and the state of the interconnected system. Dams following Atatürk Dam, are constructed for the purpose of harnessing the waters released from large-scale dams and HEPPs, (after-bay dams) (GAP,1990).

Originally designed and planned in the 1960s, GAP intends to harness the potential of the Euphrates and Tigris Rivers and their tributaries by building 22 high dams and 19 hydro-power plants. These will generate 27 billion kWh of electricity a year and irrigate 1.7 million hectares of farm land. The plains around Urfa and Harran are being irrigated with water from the Euphrates piped through twin tunnels, 26 km long each, opened in 1994. The impact on the economy of the region is dramatic. Many Turkish crops will double or even triple. GAP will provide food self-sufficiency in Turkey and will create 3.3 million jobs.

Elamli II Dam

Seyhan Dam