英语翻译Disappearing DeltaThe fertile land of the Nile delta is

英语翻译
Disappearing Delta
The fertile land of the Nile delta is being eroded along Egypt's Mediterranean coast at an astounding rate,in some parts estimated at 100 metres per year.In the past,land scoured away from the coastline by the currents of the Mediterranean Sea used to be replaced by sediment brought down to the delta by the River Nile,but this is no longer happening.
Up to now,people have blamed this loss of delta land on the two large dams at Aswan in the south of Egypt,which hold back virtually all of the sediment that used to flow down the river.Before the dams were built,the Nile flowed freely,carrying huge quantities of sediment north from Africa's interior to be deposited on the Nile delta.This continued for 7000 years,eventually covering a region of over 22000 square kilometres with layers of fertile silt.Annual flooding brought in new,nutrient-rich soil to the delta region,replacing what had been washed away by the sea,and dispensing with the need for fertilizers in Egypt's richest food-growing area.But when the Aswan dams were constructed in the 20th century to provide electricity and irrigation,and to protect the huge population centre of Cairo and its surrounding areas from annual flooding and drought,most of the sediment with its natural fertilizer accumulated up above the dam in the
southern,upsteam half of Lake Nasser,instead of passing down to the delta.