declivity, possibly appearing also in other river names in the region such as Yarkon and Yarmouk, or it may be related to the Egyptian loanword 'yǝʾor' ('big river', the Nile). According to this hypothesis, "Den" might be linked to the Akkadian word dannum for "powerful". Cognates of the word are found in Aramaic, Hebrew, Mandaic, and other Semitic languages. The first recorded use of the name appears as Yārdon in Anastasi I, an ancient Egyptian papyrus that probably dates to the time of Rameses II. Early Arab chronicles referred to the river as Al-Urdunn. In Mandaic, the etymologically related term Yardena () can refer not only to the Jordan River, but also any other body of flowing water that can be used for Mandaean baptismal rituals (masbuta). After the Crusades, the Arabic name Nahr Al Sharieat (), literally "the watering place" began to be used, and was recorded by medieval geographers such as Abu'l-Fida and Al-Dimashqi. The name was shown in various forms on most notable 19th century maps of the region, and was described by Edward Robinson in his Biblical Researches in Palestine. Although historical sources do not appear to make this distinction, it is described in some modern sources as the name for the part of the river before it flows into Lake Tiberias. History 19th century In the 19th century the River Jordan and the Dead Sea were explored by boat primarily by Christopher Costigan in 1835, Thomas Howard Molyneux in 1847, William Francis Lynch in 1848, and John MacGregor in 1869. The full text of W. F. Lynch's 1849 book Narrative of the United States' Expedition to the River Jordan and the Dead Sea is available online. 20th century In 1964, Israel began operating a pumping station that diverts water from the Sea of Galilee to the National Water Carrier. Also in 1964, Jordan constructed a channel that diverted water from the Yarmouk River, a main tributary of the Jordan River, to the East Ghor Canal. Syria has also built reservoirs that catch the Yarmouk's waters. Environmentalists blame Israel, Jordan and Syria for extensive damage to the Jordan River ecosystem. In modern times, the waters are 70% to 90% used for human purposes and the flow is greatly reduced. Because of this and the high evaporation rate of the Dead Sea, as well as industrial extraction of salts through evaporation ponds, the Dead Sea is rapidly