The silt from the Nile River has been used as a crop fertilizer for thousands of years. After the construction of the Aswan High Dam, which of the following occurred? A.
More silt was carried down river, jamming electrical turbines and preventing the dam from generating electricity.
B.
More silt was carried down river, and agricultural production increased as a result.
C.
Less silt was carried down river, so farmers began to use more chemical fertilizers.
D.
Less silt was carried down river, protecting the Nile River Delta from further damage.

Less silt was carried downriver, so farmers began to use more chemical fertilizers.

Explanation:

The Aswan Dam was built for several purposes, such as protection of cultural heritage, production of electricity, and better-regulated irrigation. One thing that has happened as well was that the floods of the Nile River after the Aswan Dam almost disappeared, while the amount of silt that the river was carrying drop significantly. While the dam has had many positive effects, that can not be said about agriculture.

Because the amounts of silt became much lower, the natural fertilizer disappeared, thus the soil became less fertile. In order to produce the same amounts of goods or at least near those amounts, the farmers had to start using fertilizers. Over time, the usage of fertilizers has constantly been increasing and with it the expenses of the farmers, so their profit was going down, while in meantime the water and soil were getting polluted.