Wednesday, January 29, 2014

The Shrinking Delta

Egypt's fertile Nile Delta is shrinking:
Prior to the building of the Aswan High Dam in the 1960s, more than 120 million tonnes of silt washed down the Nile each year and accumulated in its delta. Without this annual silt flow to replenish it, the Nile Delta is shrinking – in some places the coastline is receding by as much as 175 metres a year.
The Egyptian government has attempted to slow the sea’s advance by building a series of breakwaters and earthen dykes along the northern coast and its waterways. Piles of concrete blocks help reduce coastal erosion, but without new sedimentation, the delta land has compacted and thousands of hectares now lie at sea level...
El-Rayis warns that as the delta substratum becomes more porous, seawater has begun to infiltrate the Nile Delta aquifer, a vital source of underground water spread over 2.5 million hectares.
Saltwater has always been a threat to coastal agricultural land, but salinity was traditionally kept in check by a steady flow of freshwater covering the soil and flushing out the salt. As Egypt’s population has expanded, upstream demand on water has increased, reducing the amount of Nile water that reaches the Delta. What does trickle in these days is choked with sewage and industrial toxins.

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