In southern Egypt, the sandy desert turned, temporarily at least, into a lakes region. From 1998 to 2013, lakes quickly appeared and almost as quickly disappeared from Egypt’s Sahara Desert. Landsat captured this remarkable change.
These images also show the progress of the Toshka Project. Originally intended to relocate millions of Egyptians from overcrowded cities into a “New Nile Valley,” the project includes plans for hundreds of thousands of hectares of irrigated farmland. Like the lakes that formed in this region, this irrigation project relies upon water from the Nile River. The Toshka Project remains incomplete and the ambitious plan’s future is in question.
The Aswan High Dam on the Nile River was completed in 1970 for flood protection and to store water during dry years. The dam formed Lake Nasser, the third largest reservoir in the world by volume. A small portion of this lake is visible in the lower right corner of the images.
In 1978, a spillway and channel were built as a precaution against any unexpected increase in Lake Nasser’s water level. The channel can divert water from the reservoir to the Toshka basin, which is located outside the Nile basin. This design reduces pressure on the dam and protects downstream areas from massive flooding.
In 1998, excess rainfall in the Ethiopian highlands tested the flood control plan. The huge reservoir reached its maximum stage of 183 meters above sea level in September. The overflow water streamed through the spillway and into the Toshka basin forming the Toshka lakes. Around 32 to 98 million cubic meters of water per day poured into the basin during September and October.
The lakes reached their maximum collective size in August 2001. Their area remained fairly stable through August 2003. The water supply from Lake Nasser continuously replaced water lost through evaporation. As the level of Lake Nasser subsided, the water supply from the reservoir stopped and the lakes started diminishing.
The only two places for water in this arid region to go are into the air or into the ground. The underlying limestone prevents much ground infiltration. In the Toshka region, annual precipitation averages a meager 1.5 millimeters, and the potential evaporation rate is 14–15 millimeters per day. With no natural outlet and reduced water input to these lakes from Lake Nasser, the water evaporated quickly.
These close-ups of one of the larger lakes show how the formation and reduction of the lakes affected sand dunes.
- Sand dunes became inundated as the lakes formed. In the 2001 image, many larger dunes were small islands in the lake.
- Bright sand dunes re-emerged as the lake level dropped. In the 2013 image, a few dunes are still islands.
- The darker ground in the 2013 image indicates former water levels—the darker tone means moistened ground.
As part of the Toshka Project, a pumping station sends water from Lake Nasser to irrigated fields in the Toshka basin. The Mubarak Pumping Station has a discharge capacity of 1.2 million cubic meters per hour through the Sheikh Zayed Canal.
The pump house is like an island. Its 24 vertical pumps are arranged in two parallel lines. The intake channel is 50 meters deep, the deepest inland channel ever built. This innovative engineering marvel is even earthquake-proof.
About 138 kilometers of canals carry the Nile water from the pumping station in Lake Nasser to irrigated fields west of the reservoir. In the 2013 image, the Sheikh Zayed Canal makes a clearly visible line to the northwest from the bay where the pumping station sits.
The Landsat images show the appearance of center-pivot irrigation fields near one of the diminishing lakes. As of 2012, however, only about 21,000 hectares of farmland, less than 10% of what was planned, had been cultivated in the region.
The economic viability of this huge project has been unclear. It’s impossible to say exactly how much the Toshka Project has cost so far—estimates of the project’s final cost range up to $70 billion USD.
The availability of water from the Nile links the irrigated fields in the basin and the formation of the Toshka lakes. Excess water from Lake Nasser flowing into the Toshka lakes is likely a rare event. And if more water is pumped from the reservoir to irrigate hundreds of thousands of hectares of farmland outside the Nile basin, Lake Nasser will never again be at a high enough level to spill into the Toshka lakes.
Will people find enough incentive to move to the area and develop it into a “New Nile Valley”? Landsat will continue to track the status of the Toshka region and its agricultural development.