Lake Moeris
In prehistoric times, the canal was a natural offshoot of the Nile which created a lake to the west during high floods. Beginning with the 12th dynasty, the waterway was enlarged and the Fayyum was developed to enlarge Lake Moeris. The canal was built into the natural incline of the valley, creating a channel 15 km long and 5 m deep that sloped into the Fayyum depression. The canal was controlled by the Ha-Uar Dam, which was actually two dams that regulated the flow into the lake and out of the Nile. As the surrounding area changed at about 230 BC, the Bahr Yussef eventually became neglected, leaving most of Lake Moeris to dry up creating the depression that exists today and the modern province of Al Fayyum.