A family stares at us with a mixture of curiosity and amusement from a house perched on stilts above the river bank. Admittedly we're a bit of an odd spectacle - five people on a boat, plunging a red thermos flask, ornately decorated with pink roses, into the delta. The flask is then hauled out and its murky content carefully transferred into a series of beakers.

Despite the fact the flask would look more at home in one of Myanmar's teashops, our activity is entirely scientific. We're measuring the salinity of the water in the Irrawaddy Delta, the area that bore the brunt of Cyclone Nargis in May.

Seven months have now passed since the cyclone struck, killing more than 130,000 people and affecting another 2.4 million. The region is slowly recovering. People around Laputta, one of the hardest hit areas, are rebuilding their homes and have replanted their crops. Aid agencies such as Merlin have been busy ensuring that the people living in the delta have access to health care, food and clean water.

It is the latter which concerns us the most now. The dry season is just beginning, and with community ponds, water tanks, wells and storage facilities damaged or contaminated by the tidal surge, there is a real fear that water will become a scarce commodity when the dry season peaks in April and May. An estimated 78,000 people are expected to face shortages in the Laputta district alone.

The Delta opens out onto the Bay of Bengal, meaning that southern stretches of the river are saline whilst the more northern parts are fresh water. As the dry season advances, what is known as the salt/fresh water interface moves up the Delta, as less fresh water arrives from inland rivers. Waterways in the affected area become progressively more saline as the dry season wears on.

Drinking water shortages are therefore not new to the Delta region. Each year, many communities' water ponds are insufficient to last throughout the dry season, and villages without access to freshwater sources are faced with the challenge of importing water from other villages with more extensive ponds. Pre-cyclone, it was usually just a case of buying water from the nearest village, and a whole industry of boat-borne water vendors thrived during the season.

However, following Nargis, more villages will find their fresh water supplies dwindling earlier due to salt water contamination to ponds during the tidal surge. Many of the boats used by the villagers and by water vendors were also destroyed in the cyclone and those who still have transport will probably have to go much further afield to find water. More critically still, people just don't have the resources they normally do to buy water, having had their assets and livelihoods destroyed by Nargis.

Maryanne Leblanc, Merlin's water and sanitation manager emphasises how important it is that agencies act now to address a threat that could otherwise develop into a new disaster for an area only just now recovering.

"It is vital that we don't just sit back and wait to see what will happen at the height of the dry season," Leblanc says. "We have a window of opportunity to act now to make sure that the people living in the Delta don't face a renewed risk of displacement and disease because of a shortage of drinking water."

So our red thermos has the important job of showing us at which point the salt water reaches the fresh water. Once we know this we will have a clearer idea of which villages are going to have problems first.

Ever since Nargis struck, Merlin has been working hard to counteract water shortages. There has been an extensive programme to clean community drinking water ponds, rebuild damaged water tanks and distribute jerry cans and water filters. In doing this, Merlin is trying to restore people's ability to cope with water scarcity as the dry season takes hold, as well as ensure that the water people consume is safe.

The installation of six reverse osmosis units has played a crucial part in Merlin's response. These ingenious machines - a baffling array of blue tubes which feed into cylindrical metal tanks and a huge water bladder - transform the saline water pumped from the village ponds or river into clean, potable water.

The reverse osmosis units will be key in providing water to communities where it is scarce. Producing up to 34,000 litres a day, a reverse osmosis unit not only supplies enough drinking water for the village it is situated in, but for surrounding communities as well.

As our boat continues down the river to the next water testing spot, it is easy to enjoy the beauty of the area - the huge wide expanses of calm water, the mangroves, the houses balanced perilously on stilts along the water's edge. But this seasonal tranquility - free from the lashing rain and rough water apparent in the aftermath of the cyclone - masks a new burden for the delta's population.

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