Egypt's economy depends mainly on agriculture, media, petroleum imports, natural gas, and tourism; there are also more than three million Egyptians working abroad, mainly in Saudi Arabia, the Persian Gulf and Europe. The completion of the Aswan High Dam in 1970 and the resultant Lake Nasser have altered the time-honored place of the Nile River in the agriculture and ecology of Egypt. A rapidly growing population, limited arable land, and dependence on the Nile all continue to overtax resources and stress the economy.