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,
Grand Ethiopian Renaissance Dam govern the impacts during the reservoir filling phase include the initial reservoir elevation of the Aswan High Dam, the rainfall that occurs during the filling period and the negotiated arrangement between the three countries. These studies also show that only through close and continuous coordination, the risks of negative impacts can be minimized or eliminated. The reservoir volume (74 billion cubic meters) is about 1.5 times the average annual flow (49 billion cubic meters) of the Blue Nile at the Sudanese-Egyptian border. This loss to downstream countries could be spread over several years if the countries reach an agreement. Depending