The Sadd El-Ali Aswan High Dam, inaugurated in 1971, compensates for the fluctuating water flow of the Nile. The permanent irrigation that has become possible guarantees several harvests a year. On the other hand, the dam has serious ecological consequences for the ecosystem of the river oasis, including declining soil fertility and the salinisation of the irrigation areas.
Aswan High Dam and Nasser Reservoir
For millennia, the Nile was both a “blessing and a curse” for the Egyptian fellahs (farmers) living in the river oasis (Fig. 1). Every year from the end of July to November, a tidal wave poured into the Nile Valley. This so-called ” Nile sill ” flooded the areas near the bank and covered them with a layer of fertile mud that fertilized the soil. The rest of the year the tide was low. The water level sank by up to eight meters.
However, the Fellahs have known since time immemorial how to compensate for the changing water levels of the Nile through sophisticated irrigation techniques. They were masters in building pumping stations and irrigation canals.
This enabled the water of the Nile sill to be saved into the low water period.
Nevertheless, there were repeated famines in the Bible called “lean years” . Too low a Nile threshold was not sufficient for irrigation, and too high a threshold destroyed the irrigation systems.
To compensate for the natural fluctuations in the water level of the Nile, the Aswan Sadd El-Ali dam was built with financial and technical help from the former Soviet Union, which created the Nasser reservoir.
Aswan Dam data
|Construction time:||11 years, from 1960 to 1971|
|Building-costs:||around 2.2 billion euros|
|Length of the dam:||3 500 meters|
|Height of the dam:||110 meters|
|Length of the reservoir:||550 kilometers|
|Width of the reservoir:||up to 10 kilometers|
|Area of the reservoir:||approx. 5,000 km² (Bodensee 520 km²)|
|Capacity:||approx. 160 billion m³, of which 90 billion m³ for the absorption of the Nile floods|
The dam and reservoir initially brought the hoped-for effects to Egypt:
The dam enables the water flow to be regulated and guarantees continuous irrigation, which in turn enables several harvests a year to be achieved (Fig. 3). Flood disasters and periods of extreme low water, such as the one in the 80’s with famine, could be overcome as biblical “Egyptian plagues”.
The agriculturally usable irrigation areas in the Nile Valley could be expanded by around a quarter (approx. 7 million hectares).
The power plant’s turbines provide urgently needed electrical energy for large parts of Egypt. They also supply a new fertilizer factory and iron and aluminum smelters near Aswan.
However, human intervention in the Nile Valley’s ecosystem was also associated with problems and far-reaching negative consequences for the ecology of the bank landscape, which were already apparent during construction:
The reservoir flooded a large number of settlements and destroyed valuable cultural treasures. Almost 100,000 people had to be relocated at considerable expense. Even more expensive was the preservation of unique historical temples that threatened to swallow the water. Between 1964 and 1968, for example, the Abu Simbel rock temples, which are part of the world cultural heritage, were saved on the initiative of UNESCO. The great temple was carved 63 m deep into the rock. In front of him were the colossal statues of Ramses II and the queen.
The temples first had to be cut into 1036 large blocks. Then they could be transported to a plateau that was 60 m above the reservoir. There they were then rebuilt under two protective concrete vaults.
The reservoir also causes considerable water losses. In the desert climate, significantly more precious water evaporates over its huge water surface than originally calculated. More water than calculated also seeps into the fissured subsoil.
One of the most important problems arises from the fact that the fertile Nile mud mainly settles in the reservoir. It is therefore lost as fertilizer for the fields and has to be replaced by mineral fertilizers. Where the fellahs are financially unable to do so, soil fertility inevitably decreases considerably.
The absence of sludge deposits also changed the situation in the Nile Delta. The delta used to grow out into the sea. Additional cultivated land could be gained. Today the ocean currents gnaw the coast and tear away up to 30 m of valuable land every year.
Increased use of mineral fertilizers on year-round irrigated areas can lead to salinisation of the soil in the desert climate. The water, which is constantly abundant through the Aswan Dam, dissolves the nutrients in the soil. Due to the high air temperature, however, the salty soil water rises relatively quickly to the surface and evaporates there. What remains are the salts that form crusts. However, plants no longer grow on such salt crusts. In the past, the salt deposits were washed out by the Nile sills and washed into the sea. It is expensive to build drainage canals that have the same effect. This is one of the reasons why the soil fertility is seriously deteriorating in large areas of the Nile oasis.
The extent and weight of the ecological effects caused by the Aswan Dam on the banks of the Nile reinforce the voices that speak of a bad investment in this construction, which is intended to be a work of the century.