<P> 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 . </P> <P> 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 . </P> <P> 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 . </P> <P> 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 . </P>

What can the nile river's flooding be described as