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 Dam including Sir Benjamin Baker and Sir John Aird, whose firm, John Aird & Co., was the main contractor. In 1952, the Greek-Egyptian engineer Adrian Daninos began to develop the plan of the new Aswan Dam. Although the Low Dam was almost overtopped in 1946, the government of King Farouk showed no interest in Daninos's plans. Instead the Nile Valley Plan by the British hydrologist Harold Edwin Hurst to store water in Sudan and Ethiopia, where evaporation is much lower, was favored. The Egyptian position changed completely with the overthrow of the monarchy, led by the Free Officers Movement including Gamal