The Medjerda River originates in the
Tell Atlas, part of the
Atlas Mountains, in northeastern Algeria and then flows eastwards to Tunisia, then entering the
Gulf of Utica of the
Mediterranean Sea. Its course has a length of . It is the most important and longest river in Tunisia and is dammed in several locations, being a major supplier of water to the country's wheat crops. The Gulf of Utica was formed during the postglacial transgression about 6,000 years ago. Over time, fluvial deposits from the Medjerda gradually filled up the northern part of the gulf. The succession of events during historical times has been inferred from ancient documents and archaeological evidence. Besides morphological ground observations, aerial and satellite photographs have been used to analyze how the landscape has evolved over the past 3,000 years. The gulf's southern part was filled up in late ancient times. The sea gradually withdrew from the northern part during the Middle Ages and modern times. The Ghar el Melh lagoon is the last vestige of what used to be the Utica gulf. Following the last big flood in 1973, the Medjerda shifted, once again, its course. It now flows through a canal originally dug to evacuate the overflow of flood waters. ==History==