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.
Conflict about the waters of the Jordan River was a contributing factor to the Six-Day War when, starting in 1965, Syria attempted to divert some of its headwaters in collaboration with Lebanon and Jordan. The diversion works would have reduced the water availability for Israel's carrier by about 35%, and Israel's overall water supply by about 11%.
Jordan receives 50,000,000 cubic metres (1.8×10 cu ft) of water from the river, a quantity which is regulated by the 1994 peace treaty with Israel. In the past, one of the main water resources in Jordan was the Jordan River, with a flow of 1.3 billion m3 per year (BCM/yr). However, after Israel built the National Water Carrier in 1953 and diverted water from Lake Tiberias to Israel’s coastal plains and southern desert, the flow of the Lower Jordan River dropped significantly. The 50 MCM/yr that Israel provides from Lake Tiberias as part of the 1994 peace treaty was meant to compensate for this loss. A 2010 study found that the Lower Jordan River has been reduced to 2% of its historic flow. Water quality has also deteriorated sharply, with high levels of salinity and pollution from agricultural fertilizer and untreated wastewater upstream in Israel and the West Bank.
The New Testament speaks several times about Jesus crossing the Jordan during his ministry (Matthew 19:1; Mark 10:1), and of believers crossing the Jordan to come hear him preach and to be healed of their diseases (Matthew 4:25; Mark 3:7–8). When his enemies sought to capture him, Jesus took refuge at Jordan in the place John had first baptised (John 10:39–40).
A small section of the northernmost portion of the Lower Jordan, the first ca. 3-kilometre (1.9 mi) below the Sea of Galilee, has been kept pristine for baptism and local tourism. Most polluted is the 100-kilometre downstream stretch—a meandering stream from above the confluence with the Yarmouk to the Dead Sea. Environmentalists say the practice of letting sewage and brackish water flow into the river has almost destroyed its ecosystem. Rescuing the Jordan could take decades, according to environmentalists. In 2007, Friends of the Earth Middle East (FoEME) named the Jordan River as one of the world's 100 most endangered ecological sites, due in part to lack of cooperation between Israel and neighboring Arab states. The same Environmentalist organization had said in a report that the Jordan River could dry up by 2011 unless the decay was stopped. The flow rate of the Jordan River once was 1.3 billion cubic metres per year; as of 2010, just 20 to 30 million cubic metres per year flow into the Dead Sea. Recent literature shows the role of power asymmetries and of discourses and narratives in shaping hydropolitics along the Jordan River Basin.
Evidence from scriptures and archaeological findings has concluded that the site called Al-Maghtas on the Jordanian side is the most accurate location for the Baptism of Jesus and the ministry of John. This has led to choosing Al-Maghtas as a UNESCO World Heritage site, which took place in 2015.
