Manufactured Landscapes and the Ecosystem | The Aswan Dam + Toshka Project
This week we have been thinking a lot about the effects that big infrastructures have on ecosystems. The discussions around Owens Lake, the way it was transformed by diversing its water through the aqueduct and the future plans for a solar farm on the Owens Lake Playa has driven us to make a reflection around these issues.
The Aswan High Dam, built in the 1960s, created major change in one of the world’s largest and most famous rivers. The dam stopped the annual flooding that provided new fertile soil each year, the basis for agriculture in ancient Egypt, the world’s longest existing civilization. The decrease in water flow below the dam also changed the eastern Mediterranean Sea. Prior to the dam construction, Mediterranean water was less salty than regular sea water because its waters mixed with freshwater from the Nile.
Damming the Nile has caused a number of environmental and cultural problems. We can read here that it flooded much of lower Nubia and over 60,000 people were displaced. Lake Nasser flooded valuable archaeological sites such as the Buhen fort. The valuable silt which the Nile deposited ashore in the yearly floods and made the Nile floodplain fertile is now held behind the dam. Silt deposited in the reservoir is lowering the water storage capacity of Lake Nasser. The article adds:
Poor irrigation practices beyond the dam are water logging soils and bringing salt to the surface. Mediterranean fishing declined after the dam was finished because nutrients that used to flow down the Nile to the Mediterranean were trapped behind the dam.
Some of the significative changes mentioned above include the creation of Lake Nasser, with a maximum water level of 183 m above sea level. In 1978 Egypt began building the Sadat Canal from Lake Nasser through Wadi Toshka to allow water levels higher than 178 m to be drained off into a depression at the south end of the Eocene limestone plateau. Now, for the Toshka Project, some of the water from Lake Nassar is being pumped 320 kilometres northwest out of the Nile Valley into natural geological depressions in the Great Desert. At this point, the water forms new lakes, that astronauts began noticing in November 1998.
Starting in 2002, astronauts have seen the lakes slowly decline, with the telltale ring of darker, moistened ground showing the previous higher water levels. The rise and fall of Toshka Lakes and the economic development surrounding the region are dependent on climate fluctuations and water agreements with upstream countries that, in turn, determine the long-term water flow in the lower Nile.
In addition to the pumping station itself, the Toshka Project also involves the construction of 50km of main transfer canal, four additional 22km side branches and 800m of feeder pipeline. From the Toshka Project:
Described as a venture which “has expanded the boundaries of civil engineering,” the Mubarak Pumping Station is situated adjacent to Lake Nasser and has a discharge capacity of 1.2 million m³/hr. Its innovative design places the pump-house like an island in a lake – completely surrounded by water with 24 vertical pumps arranged in two parallel lines along both sides. 18 of these load-controlled adjustable speed units run continuously with three offline at any one time for rolling maintenance and a further three held in reserve. This arrangement, together with the use of an open 50m-deep intake channel – the deepest inland channel ever constructed – rather than a feeder canal, allowed the pump-house itself to be smaller, yielding reduced capital and run-on costs.
It has been well documented that the Toshka Lakes west of Lake Nasser have decreased greatly over the years, exposing the former dune fields [dunes appear as islands in the lake], and leaving a “bath-tub ring” of wetlands surrounding the lake shorelines. There was no way farmers in the region could continue under the constant threat of serious flooding and serious droughts. Are these the kind of new cities that we want?