How did the Aswan High Dam reduce the amount of silt reaching Egyptian farmland?

The Aswan High Dam reduced the amount of silt reaching Egyptian farmland by exerting complete control over the Nile River’s annual flooding.1

By impounding the river's floodwaters within its massive reservoir, Lake Nasser, the dam traps the water's load of rich, fertilizing silt. Consequently, this nutrient-rich sediment is no longer carried downstream to be deposited on agricultural lands by the river's rising waters. This loss of natural fertilization has forced farmers to rely on artificial fertilizers, which have proven to be an inadequate substitute for the 40 million tons of silt that were formerly deposited annually.1