<P> The Aswan High Dam is 3,830 metres (12,570 ft) long, 980 m (3,220 ft) wide at the base, 40 m (130 ft) wide at the crest and 111 m (364 ft) tall . It contains 43,000,000 cubic metres (56,000,000 cu yd) of material . At maximum, 11,000 cubic metres per second (390,000 cu ft / s) of water can pass through the dam . There are further emergency spillways for an extra 5,000 cubic metres per second (180,000 cu ft / s), and the Toshka Canal links the reservoir to the Toshka Depression . The reservoir, named Lake Nasser, is 550 km (340 mi) long and 35 km (22 mi) at its widest, with a surface area of 5,250 square kilometres (2,030 sq mi). It holds 132 cubic kilometres (1.73 × 10 cu yd) of water . </P> <P> Due to the absence of appreciable rainfall, Egypt's agriculture depends entirely on irrigation . With irrigation, two crops per year can be produced, except for sugar cane which has a growing period of almost one year . </P> <P> The high dam at Aswan releases, on average, 55 cubic kilometres (45,000,000 acre ⋅ ft) water per year, of which some 46 cubic kilometres (37,000,000 acre ⋅ ft) are diverted into the irrigation canals . </P> <P> In the Nile valley and delta, almost 33,600 square kilometres (13,000 sq mi) benefit from these waters producing on average 1.8 crops per year . The annual crop consumptive use of water is about 38 cubic kilometres (31,000,000 acre ⋅ ft). Hence, the overall irrigation efficiency is 38 / 46 = 0.82 or 82% . This is a relatively - high irrigation efficiency . The field irrigation efficiencies are much less, but the losses are reused downstream . This continuous reuse accounts for the high overall efficiency . </P>

What problem did answar dam create on nile