Bangladesh is dominated by water. The Himalayan Rivers, the Ganges and the Brahmaputra divide the country into four major regions, only one tenth of the land is more than 10m above sea level, and one third of it floods every year during monsoon season. It also dominates Bangladeshi's health system. Water-related diseases cause nearly a quarter of all deaths, and arsenic and salt contaminate drinking water supplies. In some areas, such as the Satkhira district in southwest Bangladesh, the water is becoming increasingly saline due to climate change and unregulated shrimp farming.

Not surprisingly, Bangladesh is one of WaterAid's top priorities - the charity has worked there since 1986, linking with local partner organisations to improve sanitation and access to potable water. So when WaterAid got involved with the Prix Pictet photography prize, it found a natural fit with Munem Wasif, a Bangladeshi who'd reached the final of its first contest, rewarding photography focusing on environmental sustainability. Wasif didn't win the £50,000 prize (it went to Canadian photographer Benoit Acquin for his series Chinese Dust Bowl), but he did win the £20,000 Prix Pictet commission to help WaterAid record its work in his homeland.

Open brief

Originally, the plan was for Munem to travel to the Chittagong Hills Tracts project, where WaterAid is improving sanitation and access to fresh water with Prix Pictet's support. But the area is riven by violence and, in the face of deteriorating security, Wasif and WaterAid were forced to rethink. Instead, he went to Satkhira, to document the effects of rising salinity on the local population.

'My brief was just a few lines - salinity in the coastal belt and its impact on people,' says Wasif. 'I was completely free to interpret the story in my own way. So I started to work with WaterAid's local partner, Shushilon, going with them mile after mile on motorbike to meet local people.'

Wasif is a very successful young photojournalist - besides shooting editorial for Le Monde and Asian Geographic, the 28-year-old has staged solo exhibitions at Visa pour l'Image and Chobi Mela, and is represented in Europe by Agence Vu. But his work has largely been self-funded and initiated, so at first, he says, he unsure of how to tackle the commission. 'It was different, because it sounded an NGO development topic and there were a few stereotypical images out there,' he says. 'And you can't show salinity in a photograph.

'I went to the places where they have most problems, talking to experts and local people. I did short interviews with at least 50 people and they told me their story, then I just followed it. I realised salinity is such a big problem, which affects people's whole lives. I tried to cover that, going deep and dragging out the layers. I worked the way I usually do, getting close and following people's emotions, and soon I started to feel that the story was mine - that I wanted to do it for myself.'

Practical work

Wasif made two separate trips to Satkhira, each 10 days long, and says that that too helped him find his way into the story. On the first visit he shot as much as he could - everything and anything that seemed important and relevant to the job. Then he closely edited the work, finding visual and factual themes, and getting feedback from advisors. On his return he focused more intensely on those issues, and tried to develop a closer relationship with the people he'd met.

He also faced difficult practical barriers. Motorbikes are the only reliable local transport, meaning his epic journeys around the region took many hours. And many of the locals work in Sunderban, a heavily forested coastal area, meaning that Wasif got up at 6am to follow them on their daily journey to work, walking in a narrow canal in deep mud with his camera equipment. Sunderban also offers other dangers - rife with jungle bandits, it's also home to the Royal Bengal tiger.

In total Wasif produced 40 images he was happy with, which had to be edited down to 25. Vu's corporate and cultural department director Marc Prust made the final selection with representatives from the Prix Pictet and, whilst he would have edited it slightly differently, Wasif is happy with the result. 'For me editing is always personal, that's the beauty of it.'

And ultimately, he says, the most important thing is that the project is seen. 'I don't know if I have a message or not, but this story is very, very important and I want to share it. For me, human emotions are more important than statistics.'