Why Is the Dead Sea So Salty?

Why does the Dead Sea keep all its salt?

The Dead Sea lies in the Jordan rift valley, where the continents of Africa and Asia are pulling apart and the land between them has been sinking for millennia.^[1] Rivers, most notably the Jordan River, drain into this deep basin, but no river drains out of it: the only outlet for the water is evaporation.^[1] Scientists call it a terminal lake, and its level is set by the balance between evaporation on one side and rain and runoff on the other.^[4]

As water evaporates, the water left in the lake becomes saltier.^[1] On a hot, dry summer day, NASA notes, evaporation can lower the surface by two to three centimetres.^[1] For comparison, ocean water contains about 35,000 parts per million of salt.^[6]

How much saltier is the Dead Sea than the ocean?

Figures for the Dead Sea vary by source and by year.^[2][3] A NASA image description from 2006 gives a salinity of about 300 parts per thousand, nine times that of the ocean.^[2] A 2013 World Bank overview says the water is ten times more saline than ocean water, making it one of the saltiest water bodies in the world.^[3]

Strictly speaking, the accepted definition of salinity does not apply to Dead Sea water, because of the water's peculiar chemical composition.^[4] Researchers use "quasi-salinity" instead, which is defined by how much the water's density exceeds 1,000 kilograms per cubic metre at a chosen reference temperature.^[4]

What kind of salt is in the Dead Sea?

The Dead Sea's salt is not ordinary sea salt.^[4] Its water is relatively rich in calcium, magnesium, potassium and bromine, and relatively poor in sodium, sulfate and carbonate, so its chemistry differs markedly from that of seawater.^[4] Normal seawater is dominated by sodium chloride, the familiar salt, while the Dead Sea is dominated by magnesium chloride.^[5][6]

In samples analysed for a 2010 report by Israel Oceanographic and Limnological Research (IOLR), magnesium made up on average 15.7% of the major dissolved ions, sodium 7.8%, calcium 5.6%, potassium 3.6% and chloride 66.8%.^[5] Over the long term, the share of magnesium has been rising and the share of sodium falling.^[5]

The lake's brine is also a source of minerals.^[2] In the early part of the 20th century, chemists worked out that the lake was a natural deposit of potash and bromine.^[2] According to NASA's 2006 description, Israel and Jordan produce potash, bromine, caustic soda, magnesium metal and sodium chloride from the brine, using salt evaporation pans that have diked the entire southern end of the lake.^[2]

Why do people float in the Dead Sea?

The salt makes the water dense.^[6] The U.S. Geological Survey (USGS) describes the Dead Sea's water as "extremely salty, and therefore dense", and says it holds swimmers up so that they do not sink as they would in fresh water or even in the ocean.^[6] IOLR researchers use a reference density of 1.24 grams per cubic centimetre for Dead Sea water.^[5]

How low is the Dead Sea, and how fast is it falling?

The World Bank calls the Dead Sea the lowest spot on Earth, and NASA describes the lake's surface as the lowest surface feature on Earth.^[3][1] Because the level keeps dropping, any elevation figure needs a date. On 31 August 2026, the official monthly series published by Israel's Water Authority recorded the lake at 441.33 metres below sea level.^[7]

-460-440-420-400

-441.33

198119912001200620162026

View data as a table

Dead Sea water level, late-summer readings	m relative to sea level
1981	-400.18
1986	-404.22
1991	-408
1996	-409.72
2001	-415.04
2006	-419.11
2011	-424.98
2016	-430.56
2021	-436
2026	-441.33

Source: Israel Water Authority, via data.gov.il [7] · Reading nearest to 31 August in each year

In the same series, the level fell by 10.77 metres between 31 August 2016 and 31 August 2026, an average of about 1.08 metres a year (BodaWiki's calculation from the official readings).^[7] The World Bank's 2013 overview gave a rate of 0.8 to 1.2 metres per year.^[3] In June 2026, a report by Israel's State Comptroller cited Environmental Protection Ministry estimates that the level of the northern basin would keep falling by around 1.15 metres a year without intervention.^[8]

Published levels can differ by a few metres. The World Bank put the level at about 423 metres below sea level at the end of 2012, while the Water Authority series recorded 426.78 metres below on 2 December 2012.^[3][7] The IOLR researchers Gertman and Hecht noted a 2.38-metre difference between the levels given by the Dead Sea Works and by the Hydrological Survey of Israel.^[4]

Why is the Dead Sea level dropping?

Since the early 1960s, Israel, Syria and Jordan have used the fresh water of the Dead Sea's watershed intensively, so the inflow has fallen sharply and evaporation from the lake has exceeded rain and runoff.^[4] The Jordan River is the main water body feeding the lake, and the World Bank attributes the decline to diversion of water from the Jordan River and from the Dead Sea itself.^[3]

Mineral production adds to the loss. Israel and Jordan use Dead Sea water to produce minerals, and dikes have turned the shallow southern basin into evaporation ponds filled with water pumped from the northern basin.^[4] The lake has split into two lobes, and the southern part is mostly dry except for those ponds.^[1]

By 2013, the World Bank reported, the surface area had shrunk from roughly 950 to 637 square kilometres, and the damage included the loss of freshwater springs, river bed erosion and more than a thousand sinkholes.^[3] Israel and Jordan conceived a plan to carry water from the Red Sea to the Dead Sea to halt the decline, the Palestinian Authority also agreed to the concept, and the three asked the World Bank to manage a study programme on it.^[3]