求教：尼罗河的径流量最大为什么是在秋季?

小石子儿

尼罗河流经的地区气候类型为热带草原气候和热带沙漠气候，河水的补给源以降水为主。

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husonghu

尼罗河水系由两大干支流组成: 白尼罗河(White Nile)和青尼罗河(Blue Nile). 白尼罗河发源于东非高原上的维多利亚湖，它在苏丹首都喀土穆附近与青尼罗河会合后，始称尼罗河，向北自埃及境内入海。 　　白尼罗河源于赤道地区（或赤道多雨带），上游受赤道低气压带控制，降水量季节分配均匀，河流补给量稳定；流经地区有湖泊（及沼泽）对径流量有一定的调蓄（节）作用，故径流量稳定。 　　青尼罗河的汛期出现的时段是8—11月，从气候因素分析其形成原因。此时期, 随着气压带风带的北移，非洲北部热带草原气候区因受赤道低气压带控制进入湿季，青尼罗河流域内降水明显增多，河流水量逐渐增大，进入汛期。 　　但青尼罗河对整个尼罗河的径流量的贡献大至80-90%，故它的径流量波动主导了整个尼罗河径流量的波动。(具体数据见下面的英文) 来源: http://en.wikipedia.org/wiki/Nile ---- The Nile ----www.ddhw.com The drainage basin of the Nile covers 3,254,555 km², about 10% of the area of Africa. There are two great Tributaries of the Nile: the White Nile, beginning in equatorial East Africa, and the Blue Nile, beginning in Ethiopia. Both branches are on the western flanks of the East African Rift, the southern part of the Great Rift Valley. Another less important one is Atbara which flows only while there is rain in Ethiopia and dries very fast. White Nilewww.ddhw.com The source of the Nile is sometimes considered to be Lake Victoria, but the lake itself has feeder rivers of considerable size. The most distant stream emerges from Nyungwe Forest in Rwanda, via the Rukarara, Mwogo, Nyabarongo and Kagera rivers, before flowing into Lake Victoria in Tanzania near the town of Bukoba.www.ddhw.com The Nile leaves Lake Victoria at Ripon Falls, near Jinga, Uganda, as the Victoria Nile. It flows for approximately 500 km (300 miles) farther, through Lake Kyoga, until it reaches Lake Albert. After leaving Lake Albert, the river is known as the Albert Nile. It then flows into Sudan, where it becomes known as the Bahr al Jabal ("River of the Mountain"). At the confluence of the Bahr al Jabal with the Bahr al Ghazal, itself 720 km (445 miles) long, the river becomes known as the Bahr al Abyad, or the White Nile, from the white-ish clay suspended in its waters. From there, the river flows to Khartoum. Blue Nilewww.ddhw.com The Blue Nile springs from Lake Tana in the Ethiopian Highlands. The Blue Nile flows about 1,400 km (850 miles) to Khartoum, where the Blue Nile and White Nile join to form the "Nile proper". 90% of the water and 96% of the transported sediment carried by the Nile[3] originates in Ethiopia, but this runoff happens only in summer, when the great rains fall on the Ethiopian Plateau; the rest of the year, the great rivers draining Ethiopia into the Nile (Sobat, Blue Nile, and Atbarah) flow weakly. ---Hydrologywww.ddhw.com The flow rate of the Albert Nile at Mongalla is almost constant throughout the year and averages 1048 cubic meters per second. After Mongalla the Nile is known as the Bahr El Jebel which enters the enormous swamps of the Sud region of the Sudan. More than half of the Nile’s water is lost in this swamp to evaporation and transpiration. The average flow rate in the Bahr El Jebel at the tails of the swamps is about 510 cubic meters per second. From here it soon meets with the Sobat River and forms the White Nile.www.ddhw.com The average flow of the White Nile at Malakal is 924 cubic meters per second, the peak flow is approximately 1218 cubic meters per seconds in early March and minimum flow is about 609 cubic meters per seconds in late August. The fluctuation here is due the substantial variation in the flow of the Sobat which has a minimum flow of about 99 cubic meters per seconds in august and a peak flow of over 680 cubic meters per seconds in early March.www.ddhw.com From here the White Nile flows to Khartoum where it merges with the Blue Nile to form the Nile River. Further up stream the Atbara River, the last significant Nile tributary, merges with the Nile.www.ddhw.com The White Nile contributes approximately 31% of the yearly Nile discharge. However during the dry season (January to June) the White Nile contributes between 70% and 90% of the total discharge from the Nile. During this period of time the natural discharge of the Blue Nile can be as low as 113 cubic meters per seconds, although upstream dams regulate the flow of the river. During the dry period the flow of the Atbara River will typically be zero. The Blue Nile contributes approximately 80-90% of the Nile River discharge. The flow of the Blue Nile varies considerably over its yearly cycle and is the main contribution to the large natural variation of the Nile flow. During the wet season the peak flow of the Blue Nile will often exceed 5663 cubic meters per seconds in latter August (variation by a factor of 50).www.ddhw.com Before the placement of dams on the river the yearly discharge varied by a factor of 15 at Aswan. Peak flows of over 8212 cubic meters per seconds would occur during the later portions of August and early September and minimum flows of about 552 cubic meters per seconds would occur during later April and early May. The Nile basin is complex and because of this the discharge at any given point along the river depends on many factors including weather, diversions, evaporation/evapotranspiration, and ground water flow.www.ddhw.com In 1958 radioisotope tracking led to the discovery of a subterranean river, also called a crypto-river, which flows beneath the Nile. The flow of this river is very large; estimates place the annual discharge in the range of 566 cubic km. This is equivalent to an average flow rate of almost 18,000 cubic metres per second. The discharge of this crypto-river is approximately six times the annual discharge of the Nile.

小石子儿

   真是太感谢了！英文部分我打印下来再仔细研究

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