Dhaka: IOM, the UN Migration Agency and partner aid agencies are struggling to provide clean water and sanitation for an estimated half a million people who have fled Myanmar's North Rakhine State in the last month and arrived in Cox's Bazar.

Tens of thousands of the new arrivals are still living under the open sky with little or no shelter, food or access to healthcare, said the IOM on Friday.

Daily rain has flooded campsites and left pools of water, many of them contaminated with fecal matter.

For many of the refugees, they are the only accessible water source, but pose a lethal threat of waterborne diseases like cholera.

The Inter Sector Coordination Group (ISCG), which is coordinating the emergency response and is hosted by IOM, says that approximately 59 million litres of safe water are now needed every day to meet the basic needs of the new arrivals.

Since August 25, aid agencies have managed to provide just 1.5 million litres of clean water a day to the refugee camps, makeshift settlements and spontaneous sites that now cover Cox's Bazar district.

IOM has been providing an average 12,000 litres of safe water a day to some 1,600 people in Unchiprang, one of the new spontaneous sites in Teknaf since September 15. To date, 186,000 litres of safe water has been delivered to people living in the site.

Since the new influx began on August 25, IOM has installed 387 emergency pit latrines in three sites - 40 in Unchiprang, 20 in Balukhali makeshift settlement and 327 in the new Kutupalong Expansion site.

With 50 users per latrine, they will serve an estimated 19,350 people.

It has also installed 17 mobile toilets to serve an estimated 850 people. In total, 1,532 emergency latrines have been constructed and are being maintained by IOM partners.

The IOM Water, Sanitation and Hygiene (WASH) team has also completed the boring of six deep tube wells. Installation of the wells will be completed in two weeks, providing an additional 3,000 people with clean water in the Kutupalong Expansion site.

In the makeshift settlements and spontaneous sites people desperately need more jerrycans to move and store safe water. In the last week, 15,477 jerrycans have been distributed by aid agencies.

IOM delivered 8,458 in Kutupalong makeshift settlement and Unchiprang.

Unchiprang has no access to ground water and needs an estimated 745,550 litres of water a day to be trucked in.

The water table is falling and existing water sources are losing their capacity to meet the water needs of the rapidly expanding population.

According to IOM water engineers, by January they may no longer be viable.

Before the August influx, IOM was also providing 240,000 litres of water daily for some 15,000 people living in Leda makeshift settlement.

A total of 223 deep tube wells and 1,603 different types of latrine were also in place.

But despite the earlier investment, WASH infrastructure in the settlements is now under immense strain due to the massive population increase in all sites.

Areas that are close to the border and the Naf river are in most urgent need of WASH facilities. Many sites have either no or very limited access to safe water and latrines.

The ISCG reports that an estimated 391,000 people need immediate WASH assistance.

According to IOM WASH engineers, some 18,000 emergency latrines are needed to provide access to basic emergency sanitation for all the new arrivals.

Since August 25, agencies have been able to reach only 141,070 people in Cox's Bazar district with WASH assistance.