Flooding of the Nile - wikipedia Flooding of the Nile The festival of the Nile as depicted in Norden 's Voyage d'Egypte et de Nubie The flooding of the Nile ( Arabic : عيد وفاء النيل ‎, translit. eid wafa al - nayl ) has been an important natural cycle in Egypt since ancient times. It is celebrated by Egyptians as an annual holiday for two weeks starting August 15, known as Wafaa El - Nil. It is also celebrated in the Coptic Church by ceremonially throwing a martyr 's relic into the river, hence the name, The Martyr 's Finger ( Coptic : ⲡⲓⲧⲏⲃ ⲛⲙⲁⲣⲧⲏⲣⲟⲥ, Arabic : Esba ` al - shahīd ‎ ). Ancient Egyptians believed that the Nile flooded every year because of Isis 's tears of sorrow for her dead husband, Osiris. Contents 1 Flooding cycle 1.1 Importance for Egypt 2 Agriculture 2.1 Basin irrigation 2.2 Perennial irrigation 3 End of flooding 4 See also 5 References 5.1 Citations 5.2 Bibliography Flooding cycle This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( August 2017 ) The flooding of the Nile is the result of the yearly monsoon between May and August causing enormous precipitations on the Ethiopian Highlands whose summits reach heights of up to 4550 m ( 14,928 ft ). Most of this rainwater is taken by the Blue Nile and by the Atbarah River into the Nile, while a less important amount flows through the Sobat and the White Nile into the Nile. During this short period, those rivers contribute up to ninety percent of the water of the Nile and most of the sedimentation carried by it, but after the rainy season, dwindle to minor rivers. These facts were unknown to the ancient Egyptians who could only observe the rise and fall of the Nile waters. The flooding as such was foreseeable, its exact dates and levels could only be forecast on a short term basis by transmitting the gauge readings at Aswan to the lower parts of the kingdom where the data had to be converted to the local circumstances. Which was not foreseeable, of course, was the size of flooding and its total discharge. The Egyptian year was divided into the three seasons of Akhet ( Inundation ), Peret ( Growth ), and Shemu ( Harvest ). Akhet covered the Egyptian flood cycle. This cycle was so consistent that the Egyptians timed its onset using the heliacal rising of Sirius, the key event used to set their calendar. The first indications of the rise of the river could be seen at the first of the cataracts of the Nile ( at Aswan ) as early as the beginning of June, and a steady increase went on until the middle of July, when the increase of water became very great. The Nile continued to rise until the beginning of September, when the level remained stationary for a period of about three weeks, sometimes a little less. In October it often rose again, and reached its highest level. From this period it began to subside, and usually sank steadily until the month of June when it reached its lowest level, again. Flooding reached Aswan about a week earlier than Cairo, and Luxor 5 -- 6 days earlier than Cairo. Typical heights of flood were 45 feet ( 13.7 metres ) at Aswan, 38 feet ( 11.6 metres ) at Luxor ( and Thebes ) and 25 feet ( 7.6 metres ) at Cairo. Importance for Egypt Sundown and the flooded valley near Cairo If it were not for the Nile River, Egyptian civilization could not have developed, as it is the only significant source of water in this desert region. Its other importance was its function as their gateway to the unknown world. The Nile flows from south to north, to its delta on the Mediterranean Sea. The floods were seen as the annual coming of the god. Possibly Egyptian mythology was based on this understanding, creating stories of gods or nature to give added importance to the processes and cycles that sustained Egypt. Agriculture Basin irrigation Whilst the earliest Egyptians simply laboured those areas which were inundated by the floods, some 7000 years ago, they started to develop the basin irrigation method. Agricultural land was divided into large fields surrounded by dams and dykes and equipped with intake and exit canals. The basins were flooded and then closed for about 45 days to saturate the soil with moisture and allow the silt to deposit. Then the water was discharged to lower fields or back into the Nile. Immediately thereafter, sowing started, and harvesting followed some three or four months later. In the dry season thereafter, farming was not possible. Thus, all crops had to fit into this tight scheme of irrigation and timing. In case of a small flood, the upper basins could not be filled with water which would mean famine. If a flood was too large, it would damage villages, dykes and canals. The basin irrigation method did not exact too much of the soils, and their fertility was sustained by the annual silt deposit. Salinisation did not occur, since in summer, the ground water level was well below the surface, and any salinity which might have accrued was washed away by the next flood. It is estimated that by this method, in ancient Egypt, some 2 million up to a maximum of 12 million inhabitants could be nourished. By the end of Late Antiquity, the methods and infrastructure slowly decayed, and the population diminished accordingly. By 1800, Egypt had a population of some 2.5 million inhabitants. Perennial irrigation Muhammad Ali Pasha, ( 1805 -- 1848 Khedive of Egypt ) modernized various aspects of Egypt. He endeavoured to extend arable land and achieve additional revenue by introducing cotton cultivation, a crop with a longer growing season and requiring sufficient water at all times. To this end, the Delta Barrages and wide systems of new canals were built, changing the irrigation system from the traditional basin irrigation to perennial irrigation whereby farmland could by irrigated throughout the year. Thereby, many crops could be harvested twice or even three times a year and agricultural output was increased dramatically. In 1873, Isma'il Pasha built the Ibrahimiya Canal, thereby greatly extending perennial irrigation. End of flooding Although the British, during their first period in Egypt, improved and extended this system, it was not able to store large amounts of water and to fully retain the annual flooding. In order to further improve irrigation, Sir William Willcocks, in his role as director general of reservoirs for Egypt, planned and supervised the construction of the Aswan Low Dam, the first true storage reservoir, and the Assiut Barrage, both completed in 1902. However, they were still not able to retain sufficient water to cope with the driest summers, despite the Aswan Low Dam being raised twice, in 1907 -- 1912 and in 1929 -- 1933. During the 1920s, the Sennar Dam was constructed on the Blue Nile as a reservoir in order to supply water to the huge Gezira Scheme on a regular basis. It was the first dam on the Nile to retain large amounts of sedimentation ( and to divert a large quantity of it into the irrigation canals ) and in spite of opening the sluice gates during the flooding in order to flush the sediments, the reservoir is assumed to have lost about a third of its storage capacity. In 1966, the Roseires Dam was added to help irrigating the Gezira Scheme. The Jebel Aulia Dam on the White Nile south of Khartoum was completed in 1937 in order to compensate for the Blue Nile 's low waters in winter, but it was still not possible to overcome a period of very low waters in the Nile and thus avoid occasional drought, which had plagued Egypt since ancient times. In order to overcome these problems, Harold Edwin Hurst, a British hydrologist in the Egyptian Public Works from 1906 until many years after his retirement age, studied the fluctuations of the water levels in the Nile, and already in 1946 submitted an elaborate plan for how a `` century storage '' could be achieved to cope with exceptional dry seasons occurring statistically once in a hundred years. His ideas of further reservoirs using Lake Victoria, Lake Albert and Lake Tana and of reducing the evaporation in the Sudd by digging the Jonglei Canal were opposed by the states concerned. Eventually, Gamal Abdel Nasser, President of Egypt from 1956 to 1970, opted for the idea of the Aswan High Dam at Aswan in Egypt instead of having to deal with many foreign countries. The required size of the reservoir was calculated using Hurst 's figures and mathematical methods. In 1970, with the completion of the Aswan High Dam which was able to store the highest floods, the annual flooding cycle in Egypt came to an end in Lake Nasser. In the meantime, Egyptian population has risen to 92.5 million inhabitants ( 2016 estimate ). See also Nilometer Egyptian Public Works Aswan Dam # Irrigation for agriculture Water supply and sanitation in Egypt Water resources management in modern Egypt The National Water Research Center ( Egypt ) References Citations Jump up ^ Budge, Wallis EA ( 1895 ). The Nile Notes for Travellers in Egypt. Thos. Cook & Son ( Egypt ), Ltd, Ludgate Circus, London. Jump up ^ Eyasu Yazew Hagos : Development and Management of Irrigated Lands in Tigray, Ethiopia Dissertation 2005, Delft Jump up ^ `` Population Clock ''. Central Agency for Public Mobilization and Statistics. 27 April 2013. Retrieved 11 February 2017. Bibliography Gill, Anton ( 2003 ). Ancient Egyptians : The Kingdom of the Pharaohs brought to Life. Harper Collins Entertainment. William Willcocks, James Ireland Craig : Egyptian Irrigation. Volume I ; Egyptian Irrigation. Volume II. 3rd edition. Spon, London / New York 1913. Greg Shapland : Rivers of Discord : International Water Disputes in the Middle East. C. Hurst & Co., London 1997, ISBN 1 - 85065 - 214 - 7, p. 57. ( preview on Google books ). John V. Sutcliffe, Yvonne P. Parks : The Hydrology of the Nile. International Association of Hydrological Sciences, Wallingford 1999, ISBN 978 - 1 - 901502 - 75 - 6, p. 151. ( PDF ). Wikimedia Commons has media related to Flooding of the Nile. GND : 1058992686 hide Ancient Egyptian religion Beliefs Emanationism Isfet Maat Maa Kheru Mythology Numerology Paganism Pantheism Philosophy Polytheism Soul Practices Funerals Heku Mortuary temples Offering formula Temples Veneration of the dead Deities Ogdoad Amun Amunet Heh Hauhet Kek Kauket Nu Naunet Ennead Atum Shu Tefnut Geb Nut Osiris Isis Set Nephthys Aker Akhty Ammit Am - heh Anat Andjety Anhur Anput Anubis Anuket Apedemak Apep Apis Apt Aqen Arensnuphis Ash Assessors Astarte Aten Babi Banebdjedet Bastet Bat Bata Ba - Pef Bes Buchis Cavern deities Dedun Four sons of Horus Duamutef Hapi Imset Qebehsenuef Gate deities Ha Hapi Hathor Hatmehit Hedetet Hedjhotep Heka Hemen Hemsut Heqet Hermanubis Hesat Horus Heryshaf Hu Iabet Iah Iat Ihy Imentet Imhotep Iunit Iusaaset Kebechet Khensit Khenti - Amentiu Khenti - kheti Khepri Kherty Khnum Khonsu Kothar - wa - Khasis Maahes Ma'at Mandulis Medjed Mafdet Mehen Mehet - Weret Mehit Menhit Meret Meretseger Meskhenet Min Mnevis Montu Mut Nebethetepet Nebtuwi Nefertem Nehebkau Nehmetawy Neith Nemty Nekhbet Neper Pakhet Petbe Ptah Qebui Qetesh Ra Raet - Tawy Rem Renenutet Renpet Repyt Resheph Sah Satis Sekhmet Seker Serapis Serket Seshat Shai Shed Shesmetet Shezmu Sia Sobek Sopdet Sopdu Souls of Pe and Nekhen Tatenen Taweret Tayt Ta - Bitjet Tenenet Thoth Hermes Trismegistus Tjenenyet Tutu Unut Wadjet Wadj - wer Weneg Wepset Wepwawet Werethekau Wosret Creatures Aani Abtu Bennu Griffin Hieracosphinx Medjed Serpopard Sha Sphinx Uraeus Characters Dedi Djadjaemankh Rededjet Ubaoner Locations Neter - khertet Aaru Benben Duat Land of Manu The Indestructibles Symbols and Objects Ankh Atef Atet Book of Thoth Cartouche Crook and flail Deshret Djed Egyptian obelisk Egyptian pool Eye of Horus Eye of Ra Hedjet Hemhem crown Hennu Imiut fetish Khepresh Kneph Matet boat Menat Nebu Nemes Neshmet Ouroboros Pschent Scarab Seqtet boat Serekh Shen ring Tyet Ushabti Was - sceptre Winged sun Writings Amduat Books of Breathing Book of Caverns Book of the Dead Book of the Earth Book of Gates Book of the Heavenly Cow Book of Traversing Eternity Coffin Texts The Contendings of Horus and Seth Enigmatic Book of the Netherworld Great Hymn to the Aten Litany of the Eye of Horus Litany of Re Pyramid Texts Related religions Atenism Gnosticism Hermeticism Kemetism Temple of Set Book Ancient Egypt portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Flooding_of_the_Nile&oldid=845720995 '' Categories : Egyptian culture Egyptian mythology Coptic Orthodox Church Nile Hidden categories : Articles containing Arabic - language text Articles containing Coptic - language text Articles needing additional references from August 2017 All articles needing additional references Wikipedia articles with GND identifiers Talk Contents About Wikipedia Català Deutsch Español مصرى Português Edit links This page was last edited on 13 June 2018, at 17 : 40 ( UTC ). 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Question: when does the nile river flood every year
Answer: August