The Nile is 6,690 km long, extending through 35 degrees of latitude as it flows from south to north.

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Ben Raffles        Page         18/12/2007

Introduction

The Nile is 6,690 km long, extending through 35 degrees of latitude as it flows from south to north. Its basin covers approximately one-tenth of the African continent, with a catchment area of 3,007,000 km², which is shared by eight countries: Egypt, Sudan, Ethiopia, Uganda, Kenya, Tanzania, Rwanda, and Zaire. Its main sources are found in Ethiopia and the countries around Lake Victoria.

All along the Nile's course from its most remote source, the Cagier River in Central Africa, to the Mediterranean, people are affected to some extent by the river or its water. With a few exceptions, the water resources in the headwater areas of the system are not yet much developed. The main development has taken place in the countries situated in the semi-arid and arid zones such as Sudan and Egypt. The upstream countries, however, are now considering Nile resource development projects in their territories.

The hydrological characteristics vary greatly over the basin. Rainfall in the headwater areas is abundant though seasonal. On the other hand, from about Sudan the river runs through waterless land.

The river system has two main sources of water: the Ethiopian highlands and the equatorial region around Lake Victoria. More than 60% of the river flow arriving in Egypt originates in the Ethiopian highlands by way of the ‘Sobat’, Blue Nile, and ‘Atbara’ Rivers, with the bulk of this water coming down during the summer. The rest of the flow arrives from the White Nile, which has its most remote source in Burundi. This source is a tributary, which enters Lake Victoria near the border between Uganda and Tanzania. In the equatorial region, the Nile system consists of a number of great lakes, connected either by rocky sections or swamps. The White Nile, after leaving the lake area, enters Sudan through rocky gorges and then flows through a large swamp area in southern Sudan. Although the contribution of the White Nile to the total annual flow at Aswan is only 30%, it is most important because of its timing: during the dry season from February to June its flow is large compared with that of the Blue Nile.

Egypt has always depended on the waters of the Nile River. The White Nile and the Blue Nile are the two main tributaries of the Nile. The White Nile’s source is Lake Victoria and the Blue Nile begins in the Ethiopian Highlands. In Khartoum the capital of Sudan, the two tributaries converge where they form the Nile River. The Nile flows for half of its course through country with no effective rainfall. The rainfall of the Nile is sparse compared with other major rivers in Africa such as the Zaire, Niger, and Orange Rivers. For the size of the Nile basin with its catchment area of 3,007,000 km², the annual discharge is as small as 99.5 x 109 m³, which is equivalent to 4.3% of the annual runoff. Rainfall is heavy in the headwater areas. The annual average rainfall in the lake plateau basin is about 750 mm. The heaviest rainfall occurs at Kalungala on the island of Bugola, where it averages 2,250 mm per year. Other places of high rainfall are Bukoba on Lake Victoria and Gore in Ethiopia, where the average is about 2,000 mm per year.

Before the building of a dam at Aswan, Egypt experienced annual floods from the Nile which deposited 4 million tons of nutrient-rich sediment which enabled agricultural production. This process began millions of years before Egyptian civilization began in the Nile valley and went on until the first dam at Aswan was built in 1889. This dam was insufficient to hold back the water of the Nile and was subsequently raised in 1912 and 1933. In 1946, the true threat was exposed when the water in the reservoir peaked near the top of the dam.

Before the High Dam was built, fifty percent of the Nile flow drained into the Mediterranean. During an average flood, the total discharge of nutrient salts was estimated to be approximately 5,500 tons of phosphate and 280,000 tons of silicate. The nutrient-rich flood water, or Nile Stream, was approximately fifteen kilometres wide and had sharp boundaries. It extended along the Egyptian coast and was detected off the Israeli coast and sometimes off southern Turkey.

Natural Flooding Process of the River Nile.

Before the Aswan dam was built this is how the River would have flooded and how the farmers would have used the water to irrigate their land.

Until the building of the Aswan High Dam, a farmer's life was entirely featured by the seasonal changes of weather conditions. They depended entirely on the floods, if there were no floods there would be famine. The typical farming practice was to bury seeds in dry soils before the land was covered by the following flood. The main crops that were used by the one-crop-per-year regime at ancient times were wheat and barely. Farmers used to divide an agricultural year into three main seasons; inundation, coming forth and lack of water. While the arable land was usually covered for 6 to 8 weeks during flood time by an average of about two meters of water, agriculture was abandoned during the river's low flow periods. Other non-flooded crops, e.g. vine and olives, were introduced in the Egyptian agricultural system and irrigated using lifting water devices, such as the shadouf. Petrol pumps were available but not at a cheap price.

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In all cases, as long as it acted normally, the Nile did not represent any danger to farmers. Rather, the familiarity with the change of the river directed a farmer's behaviour towards a progressive support of the water supply benefits and control of obvious dangers. This was reflected in the invention of various agriculture tools and irrigation equipment. It was only during the nineteenth century when governmental interventions in the management of the Nile system came into the construction of large-scale water structures.

The whole system was, for the first time, dealt with as an basic unit. The construction ...

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