Aswan Dam assumption did not take into account the extent of perennial irrigation that was already present throughout Egypt decades before the high dam closure. By the 1950s only a small proportion of Upper Egypt had not been converted from basin (low transmission) to perennial (high transmission) irrigation. Expansion of perennial irrigation systems in Egypt did not depend on the high dam. In fact, within 15 years of the high dam closure there was solid evidence that biharzia was declining in Upper Egypt. S. haematobium has since disappeared altogether. Suggested reasons for this include improvements in irrigation practice. In the Nile Delta,
Aswan 330, the legion stationed here received a bishop from Alexandria; this later became the Coptic Diocese of Syene. The city is mentioned by numerous ancient writers, including Herodotus, Strabo, Stephanus of Byzantium, Ptolemy, Pliny the Elder, Vitruvius, and it appears on the Antonine Itinerary. It also is mentioned in the Book of Ezekiel and the Book of Isaiah. The latitude of the city that would become Aswan – located at 24° 5′ 23″ – was an object of great interest to the ancient geographers. They believed that it was seated immediately under the tropic, and that on the day of