The dam holds back much of the rich silt that fertilized the fields during the flood season each year. Farmers in Egypt must now use artificial fertilizers, more than farmers in any other country. In addition, the flow of the Nile's waters to the Mediterranean Sea held back the salty sea water. After the dam was built, less water flowed down to the Mediterranean. Salt water now enters the delta, making some of the once fertile land unfit for farming.