In the scorching heat of the southern Israeli desert, visitors from around the world tread carefully along a sandy beachfront before stepping into the gently lapping waters of the Dead Sea, the lowest point on earth.

The sea's salty, mineral-rich water allows swimmers to float effortlessly on its surface. Its therapeutic qualities - known to assist with skin conditions and arthritis - have attracted visitors since antiquity.

But the blazing hot walk from the shore to the sea is becoming longer every year.

The bizarre body of water - located more than 420m below sea level - has been shrinking by more than a metre a year in recent decades due to damming and unsustainable uses of the region's water basins. The sea has already lost about a third of its surface area.

Scientists have warned that a regional effort is urgently required to restore water levels in the Jordan River, which feeds the Dead Sea. But a proposal to channel water from the Red Sea has been controversial, and forging international cooperation on preserving waterways has been difficult in the conflict-ridden region.

An Israeli expert on water management, Professor Eilon Adar, director of the Zuckerberg Institute for Water Research at Ben-Gurion University, said the main cause of the sea's demise was countries extracting water from the surrounding basins.

Another factor, he said, was Israeli and Jordanian industrial works at the Dead Sea which extract potash by evaporating seawater.

"The Dead Sea is dying because Israel, Jordan, Syria and Lebanon divert water from the basin," he told The Straits Times.

The shrinking of the Dead Sea reflects the broader demise of the waterways in the Middle East, including the Jordan River. Stretches of the river, particularly in the south, are all but dry.

Mr Gidon Bromberg, from EcoPeace Middle East, a non-governmental organisation which promotes international cooperation on environmental projects, said the decline of the Jordan River had been caused by a mix of increasing population, unsustainable development and a "mindset of conflict".

"Not only do countries want to grab the water for all their legitimate uses, but they also want to deny the water to their enemy," he told The Straits Times.

"The mindset is that down the river is where the enemy is, so who cares if it stinks? It became little more than a sewage canal."

Mr Bromberg, the organisation's Israeli co-director, said it was "extremely hard" to achieve regional cooperation, but some progress was being made.

In the past two years, Israel has begun releasing water into the Jordan River. Environmental groups have urged it to add more and for other countries such as Jordan and Syria to follow suit.

"All sides have responsibility," Mr Bromberg said.

"All sides need to take action if we are to reverse the situation."

The Dead Sea used to get about 1.3 billion cubic litres of water from the Jordan River, which in turn received water from lakes and tributaries across the region. But the sea now receives only about 100 million cubic litres a year, as countries have diverted water for domestic and agricultural use.

A new study by Israeli and German scientists has examined the extent of the decline in water quality and volumes in the lower Jordan River. Monitoring equipment was installed in 2010 8km north of the Dead Sea and the study said further checking was "critical" to identify extreme events and prevent impact on fauna and flora.

"The fresh surface water of the lower Jordan River has been limited in the past several decades due to damming of its main tributaries, which reduced the annual flow by 90 per cent, leaving a mixed flow of polluted and saline sources," according to the study published in the Journal Of Hydrology in June.

Waterways across Israel have suffered from pollution and reduced flows but there has been a growing push to revive them.

The Yarkon River, which runs through Tel Aviv, was once infamous for its pungent smell and dangerous toxicity, but has been cleaned up in recent decades.

In 1997, a bridge over the river collapsed and four visiting Australians died, including three due to infections from the polluted waters.

Following the disaster, the authorities worked to clean the river, preventing in-flows of sewage and industry waste.

The area is now surrounded by popular parklands and its waters teem with fish, as well as rowers and families on paddleboats.

Environmental groups say the Dead Sea and the Jordan River badly need similar efforts.

The decline of the Dead Sea has already had flow-on environmental effects, including dangerous sinkholes which have opened up around the shoreline.

Prof Adar said it was possible to revive the Jordan River by encouraging surrounding nations to rely on alternative water sources.

Israel, for instance, has become a world leader in desalination technology and now produces more than a quarter of its drinking water from its four plants. A fifth plant is about to come online.

"The Jordan River is a holy river for the entire Christian world - we have to revive it," Prof Adar said. "It is an international cross-border water source. We cannot give up on the Jordan River. "