|Países, regiones, cuencas hidrográficas|
|Usos del agua|
|Riego y drenaje|
Tipo de información
|Conjuntos de datos|
|Mapas y datos espaciales|
Info para los medios
|Visualizaciones e infografías|
|ODS Meta 6.4|
|Year: 2009||Revision date: --||Revision type: --|
|Regional report:||Water Report 34: English or Arabic|
The Euphrates–Tigris River Basin is a transboundary basin with a total area of 879 790 km2 distributed between Iraq (46 percent), Turkey (22 percent), the Islamic Republic of Iran (19 percent), the Syrian Arab Republic (11 percent), Saudi Arabia (1.9 percent) and Jordan (0.03 percent) (Lehner et al, 2008) (Table 1). The Islamic Republic of Iran is riparian only to the Tigris, and Jordan and Saudi Arabia are riparian only to the Euphrates. Both the Euphrates and the Tigris rise in the mountains of eastern Turkey and the basin has high mountains to the north and west and extensive lowlands to the south and east. Two-thirds of their courses go through the highlands of eastern Anatolia in Turkey and the valleys of the Syrian and Iraqi plateaus before descending into the arid plain of Mesopotamia (Kibaroglu, 2002). The Euphrates and Tigris join near Qurna (Iraq) in a combined flow called Shatt Al-Arab, which empties into the Persian Gulf. However, more upstream within Iraq both rivers are also connected through the construction of several canals.
Most of the Euphrates–Tigris River Basin has a sub-tropical Mediterranean climate with wet winters and dry summers. In the mountainous headwater areas freezing temperatures prevail in winter and much of the precipitation falls in the form of snow. As the snow melts in spring the rivers rise, augmented by seasonal rainfall which reaches its maximum between March and May. In southeastern Turkey as well as in the north of the Syrian Arab Republic and Iraq the climate is characterized by rainy winters and dry warm summers. Average annual precipitation in the Euphrates–Tigris River Basin is estimated at 335 mm, although it varies all along the basin area (New et al, 2002). In the Mesopotamian Plain the annual rainfall is rarely above 200 mm, while it reaches 1 045 mm in other places in the basin. The summer season is exceedingly hot and dry with midday temperatures approaching 50 ºC and with daytime relative humidity as low as 15 percent. These climatic conditions demonstrate that both the Euphrates and the Tigris flow through arid and semi-arid regions within the Syrian Arab Republic and Iraq, since 60 percent of the Syrian territory receives less than 250 mm/year of precipitation and 70 percent of Iraq receives on average 400 mm/year (Kibaroglu, 2002). The annual average temperature of the entire Euphrates–Tigris River Basin is 18 ºC. The average temperature of the basin in January is 5 ºC, though it can decrease to –11 ºC in the coldest places in the basin. In July, the average temperature of the Euphrates–Tigris River Basin reaches 31 ºC, although in the hottest places it can increase to 37 ºC (New et al, 2002).
The Euphrates originates in the eastern highlands of Turkey, between Lake Van and the Black Sea, and is formed by two major tributaries, the Murat and the Karasu. It enters the Syrian territory at Karkamis, downstream from the Turkish town of Birecik. It is the joined by its major tributaries, the Balik and Khabur, which also originate in Turkey, and flows southeast across the Syrian plateaus before entering the Iraqi territory near Qusaybah. Of the Euphrates Basin 28 percent lies in Turkey, 17 percent in the Syrian Arab Republic, 40 percent in Iraq, 15 percent in Saudi Arabia, and just 0.03 percent in Jordan. The Saudi Arabian stretch of the Euphrates dries in summer; there are no perennial rivers. The Euphrates river is 3 000 km long, divided between Turkey (1 230 km), the Syrian Arab Republic (710 km), and Iraq (1 060 km), whereas 62 percent of the catchment area that produces inputs into the river is situated in Turkey and 38 percent in the Syrian Arab Republic. It is estimated that Turkey contributes 89 percent of the annual flow and the Syrian Arab Republic 11 percent. The remaining riparian countries contribute very little water.
The Tigris, also originating in eastern Turkey, flows through the country until the border city of Cizre. From there it forms the border between Turkey and the Syrian Arab Republic over a short distance and then crosses into Iraq at Faysh Khabur. The Tigris river is 1 850 km long, with 400 km in Turkey, 32 km on the border between Turkey and the Syrian Arab Republic and 1 418 km in Iraq. Of the Tigris Basin 12 percent lies in Turkey, 0.2 percent in the Syrian Arab Republic, 54 percent in Iraq and 34 percent in the Islamic Republic of Iran. Turkey provides 51 percent, Iraq 39 percent, and the Islamic Republic of Iran 10 percent of the annual water volume of the Tigris, but because of unfavourable geographic and climatic conditions the latter cannot use the water of the Tigris for agriculture or hydropower (Kaya, 1998). Within Iraq, several tributaries flow into the river coming from the Zagros Mountains in the east, thus all on its left bank. From upstream to downstream there are:
The Shatt Al-Arab is the river formed by the confluence downstream of the Euphrates and the Tigris and it flows into the Persian Gulf after a course of only 190 km. The Karun River, originating in Iranian territory, has a mean annual flow of 24.7 km3 and flows into the Shatt Al-Arab just before it reaches the sea, bringing a large amount of freshwater.
The average annual discharge of the Euphrates and Tigris rivers together is difficult to determine due to the large yearly fluctuation. According to the records for 1938–1980, there have been years when 68 km3 were observed in the two rivers in the mid–1960s, and years when the amount was over 84 km3 in the mid–1970s. On the other hand, there was the critical drought year with less than 30 km3 at the beginning of the 1960s. Such variation in annual discharge makes it difficult to develop an adequate water allocation plan for competing water demand from each sector as well as fair sharing of water among neighbouring countries (UNDG, 2005). The annual flow of the Euphrates River Basin from Turkey to the Syrian Arab Republic is 28.1 km3, of which 26.9 km3 corresponds to the Euphrates main river, and 30.0 km3 from the Syrian Arab Republic to Iraq. The annual flow of the Tigris River Basin from Turkey to Iraq is 21.3 km3. The Tigris borders the Syrian Arab Republic only over a short distance in the east and therefore very little annul flow, estimated at 1.25 km3/year, can be available for the Syrians. The annual flow of the tributaries of the Tigris from Iran to Iraq is 10 km3.
Turkey finds itself in a strategically strong position as the only country in the Euphrates–Tigris River Basin to enjoy abundant surface water and groundwater resources. The Syrian Arab Republic depends heavily on the water of the Euphrates. Iraq is also reliant upon the Euphrates, but uses the Tigris River as well as an alternative source of water (Hohendinger, 2006).
Groundwater aquifers in Iraq consist of extensive alluvial deposits of the Tigris and Euphrates and are composed of Mesopotamian-clastic and carbonate formations. The alluvial aquifers have limited potential because of poor water quality. The alluvial aquifers contain large volume reservoirs: and annual recharge is estimated at 620 million m3 from direct infiltration of rainfall and surface water runoff.
Downstream riparian countries complain about the quality of the water. Turkey’s use of water has so far been limited mainly to hydropower generation and irrigation. While the former use is considered non-consumptive and not directly linked to water quality, the return flow from irrigation causes water pollution, which in turn affects potential downstream uses. Equally important are natural causes of environmental concern in the sense that some residual characteristics common to both rivers exacerbate the damaging effects of human pollution. Notable natural causes are the high rate of evaporation, sharp climatic variations, the accumulation of salts and sediments, poor drainage and low soil quality in the lower reaches of the Tigris and Euphrates.
In Iraq, the present quality of water in the Tigris near the Syrian border is assumed to be good, including water originating in both Turkey and Iraq. Water quality degrades downstream, with major pollution inflows from urban areas such as Baghdad due to poor infrastructure of wastewater treatment. Water quality of the Euphrates entering Iraq is less than the Tigris, currently affected by return flow from irrigation projects in Turkey and the Syrian Arab Republic, and expected to get worse as more land comes under irrigation. The quality is further degraded at such times as flood flows are diverted into off-stream storage in Tharthar and later returned to the river system. Salts in Tharthar are absorbed by the water stored therein. The quality of the water in both the Euphrates and the Tigris is further degraded by return flows from land irrigated in Iraq as well as urban pollution. The amount and quality of water entering southern Iraq from the Iranian territory is largely unknown, although it is clear that flows are impacted by irrigation return flow originating in the Islamic Republic of Iran (UNDG, 2005).
The deterioration of water quality and the heavy pollution from many sources are becoming serious threats to the Euphrates–Tigris River Basin. A problem is that there is no effective water monitoring network, making it difficult to address water quality and pollution, as the sources of pollution cannot be precisely identified. Hence, the rehabilitation and reconstruction of the water monitoring network is urgently needed for water security.
The Euphrates and Tigris were the cradle of the early Mesopotamian civilizations and irrigation made it possible for the local people to develop agriculture. This resulted in the development of great ancient civilizations, where water played an important role. Mesopotamia, the land between the Euphrates and the Tigris, remained the centre of many different civilizations and gave life to millions of inhabitants up to modern times (AU, 1997). Unfortunately, as is usually the case, the seasonal distribution of the availability of water does not coincide with the irrigation requirements of the basin. The typical low water season in the Euphrates occurs from July to December, reaching its lowest point in August and September when water is most needed to irrigate the region’s winter crops (Akanda et al, 2007). In the area close to the two river systems, rainfed farming is possible, although supplementary irrigation would raise yield and allow several cropping seasons. In the Mesopotamian Plain, however, the evaporative demand is very high and crops require intensive irrigation because of low annual rainfall and hot and dry summers. The total area equipped for irrigation in the Euphrates–Tigris River Basin is estimated to be around 6.5–7 million ha, of which Iraq accounts for approximately 53 percent, the Islamic Republic of Iran for 18 percent, Turkey for 15 percent and the Syrian Arab Republic for 14 percent. Agricultural water withdrawal is approximately 68 km3.
Iraq was the first riparian country to develop engineering projects in the basin. The Al Hindiya and Ramadi-Habbaniya dams on the Euphrates were constructed in 1914 and in 1951 respectively, both for flood control and irrigation (Kaya, 1998). By the mid–1960s, the development of irrigated agriculture in Iraq far surpassed the development in the Syrian Arab Republic and Turkey. During this period, Iraq was irrigating over five times as much land in the river basin as the Syrian Arab Republic and nearly ten times as much as Turkey. To continue its efforts to use the water of these rivers efficiently and to provide irrigation water for the land between the Euphrates and the Tigris rivers, Iraq began constructing in the 1960s a 565 km long canal, the Third River (also called Saddam River), between the Euphrates and Tigris, which was completed in 1992. In the late 1970s, as part of the effort to prevent flood damage, Iraq built another canal to divert excess water from the Tigris into Lake Thartar. Since then, Iraq has built other similar canals linking Lake Thartar to the Euphrates and again connecting the lake with the Tigris. Iraq has also built dams on the Euphrates and Tigris to produce hydropower, such as the Haditha Dam completed in 1985 (Korkutan, 2001). In 1991 a large irrigation project, the North Al-Jazeera irrigation project, was launched in order to serve approximately 60 000 ha by using a linear-move sprinkler irrigation system with water stored by the Mosul Dam. Another irrigation project, the East Al-Jazeera irrigation project, involved the installation of irrigation networks on more than 70 000 ha of previously rainfed land near Mosul. These projects were part of a scheme to irrigate 250 000 ha in the Al-Jazeera plain.
The Syrian Arab Republic began exploiting the water of the Euphrates for irrigation and hydropower in the early 1960s. The Tabqa Dam was built on the Euphrates in 1973, mainly with the help of the then Soviet Union. The purpose of this major dam was to meet the Syrian Arab Republic’s water and energy needs. The Bath Dam, completed in 1986, was the second Syrian dam on the Euphrates river. However, the hydropower capacity of the Bath Dam was not of the same scale as the Tabqa Dam. The Bath Dam had a limited capacity for electricity generation and provided relatively little water for irrigation. The Tishreen Dam, the third Syrian dam on the Euphrates, mainly designed for hydropower, is still under construction. Since the Tigris river forms the border with Turkey, the Syrian Arab Republic could not build reservoirs to store or divert the water of this river without the cooperation of its neighbour on the other bank (Korkutan, 2001).
Turkey began constructing its first dam on the Euphrates River, the Keban Dam near Keban Strait, in the mid–1960s and finished the project in 1973. The second dam on the Euphrates was the Karakaya Dam, completed in 1988. This was the first dam built as part of the implementation of the Southeastern Anatolia Project (GAP). Like the Keban Dam, the purpose of the Karakaya Dam was to produce hydropower. The third dam on the Euphrates River was the Ataturk Dam, the most important in the GAP Project, completed in 1992. It was designed to store water for large-scale irrigation as well as for the generation of hydropower (Korkutan, 2001).
Table 2 shows the large dams in the Euphrates–Tigris River Basin, i.e. dams with a height of more than 15 metres or with a height of 5–15 metres and a reservoir capacity larger than 3 million m3 according to the International Commission on Large Dams (ICOLD).
During the 20th century various bilateral attempts at cooperation were made within the Euphrates–Tigris Basin. In 1920 the French and British governments, as the mandatory powers in Mesopotamia, signed a treaty regarding utilization of the water of the Euphrates and Tigris. The Turco–French Protocol, signed in 1930, committed the Turkish and French governments to coordinate any plans to use the water of the Euphrates. The principle of mutual cooperation over water development was extended in a Protocol annexed to the 1946 Treaty of Friendship and Good Neighbourly Relations between Turkey and Iraq. The agreement encompassed both rivers and their tributaries, and both countries agreed that the control and management of the Euphrates and Tigris rivers depended to a large extent on the regulation of flow in the Turkish source areas. At that time Turkey and Iraq agreed to share related data and consult with each other in order to accommodate both countries’ interests. The 1946 Treaty mandated a committee to implement these agreements. However, none of this occurred because of different conflicts among the riparian countries (Kaya, 1998).
As the population of the region progressively increases, the demand for agricultural products increases and hence also the number of water supply projects. In 1973, Turkey constructed the Keban Dam in the Euphrates River Basin. The Syrian Arab Republic soon followed suit with the Tabqa Dam, also completed in 1973 and filled in 1975. The filling of these dams caused a sharp decrease in downstream flow and the quantity of water entering Iraq fell by 25 percent, causing tension between the countries (El Fadel et al., 2002). The tension eased when the Syrian Arab Republic released more water from the dam to Iraq. Although the terms of the agreement were never made public, Iraqi officials have privately stated that the Syrian Arab Republic agreed to take only 40 percent of the river’s water, leaving the remainder for Iraq (Kaya, 1998). In 1976, Turkey pledged to release 350 m3/s from the Euphrates downstream and later in the same year increased the minimum flow to 450 m3/s, also in an effort to reduce tensions.
In 1977, Turkey announced plans for the region’s largest water development project ever, the Southeastern Anatolia Project (GAP), which included 22 dams and 19 hydropower projects to be built on the Euphrates–Tigris. This project is intended to provide irrigation, hydropower, and socio-economic development in Turkey. The Syrian Arab Republic and Iraq fear that the project will lead to reduced river flows and leave little water for use in their countries’ agricultural and energy projects (Akanda et al, 2007). The construction of the Ataturk Dam in Turkey, one of the GAP projects, was completed in 1992.
In 1983, Turkey, Iraq and the Syrian Arab Republic established the Joint Technical Committee for Regional Waters to deal with all water issues among the Euphrates–Tigris Basin riparian countries and to ensure that the procedural principles of consultation and notification were followed, as required by international law. However, this group disintegrated after 1993 without any progress (Akanda et al, 2007).
In 1984, Turkey proposed a “Three-staged plan for optimal, equitable and reasonable utilization of the transboundary watercourses of the Euphrates–Tigris Basin”. This plan, which conforms to the principle of equitable utilization, proposes that the riparian countries jointly conduct and complete inventory studies and evaluation of water and land resources. This plan would promote objective data-gathering in the basin. After evaluation of all the data the proposed projects could be compared, based on their economic and social merits, and those deemed more beneficial could be implemented. The plan considers the basin to be a whole system, underlining the interdependence of its elements, as required by the UN Watercourses Convention (Kaya, 1998). For its part, the Syrian Arab Republic has proposed the following formula for water allocation: each riparian country will notify the other riparian countries of its demands on each river separately; the capacities of both rivers in each riparian country shall be calculated and, if the total demand exceeds the total supply of a given river (as is sure to be the case), the exceeding amount will be deducted proportionally from the demand of each riparian country (El Fadel et al, 2002).
In 1987, an informal agreement between Turkey and the Syrian Arab Republic guaranteed the latter a minimum flow of the Euphrates River of 500 m3/sec throughout the year (15.75 km3/year).
According to an agreement between the Syrian Arab Republic and Iraq signed in 1990, the Syrian Arab Republic agrees to share the Euphrates water with Iraq on a 58 percent (Iraq) and 42 percent (the Syrian Arab Republic) basis, which corresponds to a flow of 9 km3/year at the border with Iraq using the figure of 15.75 km3/year from Turkey (FAO, 2004b).
In 2001, a Joint Communiqué was signed between the General Organization for Land Development (GOLD) of the government of the Syrian Arab Republic and the GAP Regional Development Administration (GAP-RDA), which works under the Turkish Prime Minister’s Office. This agreement envisions supporting training, technology exchange, study missions, and joint projects, but is limited because it only involves Turkey and the Syrian Arab Republic (Akanda et al, 2007).
In 2002, a bilateral agreement between the Syrian Arab Republic and Iraq was signed concerning the installation of a Syrian pump station on the Tigris River for irrigation purposes. The quantity of water drawn annually from the Tigris River, when the flow of water is in the average, will be 1.25 km3, with a drainage capacity proportional to the aimed surface of 150 000 ha (FAO, 2002).
In April 2008, Turkey, the Syrian Arab Republic and Iraq decided to cooperate on water issues by establishing a water institute that will consist of 18 water experts from each country to work towards solving water-related problems among the three countries. This institute will conduct its studies at the facilities of the Ataturk Dam, the dam with the largest reservoir capacity in Turkey, and plans to develop projects for the fair and effective use of transboundary water resources (Yavuz, 2008).
Table 3 lists the main historical events in the Euphrates–Tigris River Basin.
Akanda, A., Freeman, S. and Placht, M. 2007. The Tigris-Euphrates river basin: Mediating a path towards regional water stability.
American University [AU]. 1997. Tigris-Euphrates river dispute. ICE case studies.
Comair, F.G. 2008. Gestion et hydrodiplomatie de l’eau au Proche-orient.
Comprehensive Assessment of Water Management in Agriculture. 2007. Water for food, water for life: a comprehensive assessment of water management in agriculture. London: Earthscan, and Colombo: International Water Management Institute.
Dogan Y.P. 2009. Turkey, Syria cooperate on water front. Today’s Zaman. 20 March 2009.
DSI (General directorate of state hydraulic works). XXst Regional Directorate of State Hydraulic works - Kahramanmaras.
El Fadel, M., El Sayegh, Y., Abou Ibrahim, A., Jamali, D. and El Fadl, K. 2002. The Euphrates-Tigris basin: A case study in surface water conflict resolution.
Erdem, M. (after 2002). The Tigris-Euphrates rivers controversy and the role of international law.
FAO. 1995. Irrigation in Africa/L’irrigation en Afrique en chiffres. FAO Water Report No. 7. Rome.
FAO. 1997a. Irrigation in the Near East Region in figures. FAO Water Report No. 9. Rome.
FAO. 1997b. Irrigation in the countries of the former Soviet Union in figures. FAO Water Report No. 15. Rome.
FAO. 1997c. Irrigation potential in Africa - a basin approach. FAO Land and Water Bulletin No. 4. Rome.
FAO. 1999. Irrigation in Asia in figures. FAO Water Report No. 18. Rome.
FAO. 2002. Bilateral agreement between Syria and Iraq concerning the installation of a Syrian pump station on the Tigris River for irrigation purposes. Available at http://faolex.fao.org/waterlex/.
FAO. 2003. Review of world water resources by country. FAO Water Report No. 23. Rome.
FAO. 2004. Support to the drafting of a national Water Resources Master Plan.
FAO. 2005. Irrigation in Africa in figures – AQUASTAT survey 2005. FAO Water Report No. 29. Rome.
FAO. 2008a. FAOSTAT – database. Available at http://faostat.fao.org/.
FAO. 2008b. AQUASTAT – database. Available at http://www.fao.org/nr/aquastat/.
Gleick, P.H., ed. 1993. Water in crisis: a guide to the of world’s freshwater resources. New York, USA, Oxford, UK, Oxford University Press for Pacific Institute. 473 pp.
Gleick, P.H., ed. 2006. The world’s water 2006-2007: the biennial report on freshwater resources. Washington, DC, Island Press.
Hohendinger, K. 2006. Water politics in the Middle East: The Euphrates Tigris basin.
ICID (International Commission on Irrigation and Drainage). 2005. Sprinkler and micro-irrigated area in some ICID member countries. Available at http://www.icid.org.
IPTRID (International Programme for Technology and Research in Irrigation and Drainage) /FAO. 2003. The irrigation challenge - increasing irrigation contribution to food security through higher water productivity canal irrigation systems. Issue paper No. 4.
Kaya, I. 1998. The Euphrates–Tigris basin: An overview and opportunities for cooperation under international law.
Khater, A.R. 2003. Intensive groundwater use in the Middle East and North Africa In R. Llamas & E. Custodio, eds. Intensive use of groundwater challenges and opportunities. Abingdon, UK, Balkema. 478 pp.
Kibaroglu, A. 2002. Building a regime for the waters of the Euphrates-Tigris river basin.
Korkutan, S. 2001. The sources of conflict in the Euphrates-Tigris Basin and its strategic consequences in the Middle East.
Lehner, B., Verdin, K., Jarvis, A. 2008. New global hydrography derived from spaceborne elevation data. Eos, Transactions, AGU, 89(10): 93-94. HydroSHEDS. Available at the following link: http://www.worldwildlife.org/hydrosheds and http://hydrosheds.cr.usgs.gov.
Lowi, M. After 1996. Political and institutional responses to transboundary water disputes in the Middle East.
L'vovitch, M.I. 1974. World water resources and their future. Russian ed. Mysl. Moscow. Translation in English by R.L. Nace, American Geological Union, Washington, 1979. 415 pp.
Milich, L and Varady, G. 1998. Openness, sustainability, and public participation in transboundary river-basin institutions. The Israel-Jordan Joint Water Committee (IJJWC)
Möllenkamp S. 2003. Transboundary river basin management - new challenges in EU 25 and beyond.
New, M., Lister, D., Hulme, M. and Makin, I. 2002. A high-resolution data set of surface climate over global land areas. Climate Research 2. Available at following link: http://www.cru.uea.ac.uk/cru/data/hrg.htm.
OSU (Oregon State University). 2002. International river basins of the world.
Sofer A., Rosovesky M. and Copaken N. 1999. Rivers of fire: the conflict over water in the Middle East.
UN (United Nations). 2006. The UN World Water Development Report II: Water, a shared responsibility. UNESCO / Berghahn Books.
UNDG (United Nations Development Group). 2005. The national water master plan – Phase 1 Water Resources Assessment. 26 pp.
UNDP (United Nations Development Programme). 2008. Human Development Index. Available at http://hdr.undp.org).
UNEP. 2003. GEO Year Book 2003. Theme: Freshwater.
UNESCO-IHE (Institute for water education). 2002. From conflict to cooperation in international water resources management: challenges and opportunities. Institute for Water Education Delft, The Netherlands.
UNICEF (United Nations Children's Fund). 2005. Statistics by country. Available at http://www.unicef.org
UNICEF / WHO (World Health Organization). 2008. Joint Monitoring Programme (JMP) for water and sanitation. Available at http://www.wssinfo.org.
WHYMAP (World-wide hydrogeological mapping and assessment programme). 2008. Groundwater resources of the world.
WHO (World Health Organization). 2005. World malaria report 2005.
World Bank. 1998. International watercourses: enhancing cooperation and managing conflict.
World Bank. 2007. Making the most of scarcity.
World Bank. 2008. Indicators of world development.
World Resources Institute. 1994. World resources 1994-1995. A guide to the global environment. Oxford University Press for WRI/UNEP/UNDP. 400 pp.
World Resources Institute. 2003. World resources 2002-2004. Decisions for the earth: balance, voice, and power.
Yavuz, Ercan. 2008. Turkey, Iraq, Syria to initiate water talks. Today’s Zaman 12/03/2008.
|Formato para imprimir|
^ ir arriba ^
|Citar como: FAO. 2016. Sitio web AQUASTAT. Organización de las Naciones Unidas para la Alimentación y la Agricultura. Accedido el [aaaa/mm/dd].|
|© FAO, 2016 | Preguntas o comentarios? firstname.lastname@example.org|
|Su acceso a AQUASTAT y el uso de toda su información o datos están sujetos a los términos y condiciones establecidos en el User Agreement.|