Gansu boatmen keep a hardscrabble tradition alive as they ferry tourists across the Yellow River. But the boats, made buoyant with sheep skins filled with air, may be gone in a generation, Lin Jing reports in Lanzhou.

Zhang Debao sits in the sunshine, staring at the translucent sheepskin bags on the Yellow River, which flows right through the heart of downtown Lanzhou, Gansu province's capital city.

A boatman ferries a passenger on his sheepskin raft on the Yellow River in Lanzhou, Gansu province. Photo by Lin Jing / China Daily

The smoke from the cigarette between his fingers is blown away by the cold wind in early winter. After several crossings on his sheepskin raft, he needs a break. After all, he is already 60 years old.

"We will be the last group of sheepskin raft boatmen," says Zhang, shaking his head. "There will be no one to take over our trade."

Occasionally, there are some curious visitors coming for a look at the rafts made from sheepskin bags, for a glimpse into the cultural heritage of Lanzhou.

Sheepskin rafts can be traced back to the Han Dynasty (206 BC-AD 220), when soldiers used them to ferry men and goods during wars. Local residents in Lanzhou used them to shuttle passengers, fresh fruits and vegetables across the river.

The biggest barges are made from 600 sheepskin bags, while the smaller crafts, like those used today, are made from 13 bags, and used normally for short distances only.

Despite a long history, there is only a handful still in the business, and Zhang is one of the few who can still make the sheepskin rafts himself.

The process is long and arduous, strictly following the ancient methods.

Raft-makers will select sheep in November, when the animals are fat and have thicker skins. After butchering, they will use rapeseed oil to season the skin and make it water-resistant. The skins will be dried during the coming spring and summer, when they turn yellow and transparent. Then the skins are sewn into bags.

Zhang says that these sheepskin bags are inflated by mouth only. "A bicycle pump is no good for us. When you blow with your mouth, there will be more moisture in the air, which will give these bags a longer life."

Experienced boatmen can blow up a sheepskin bag within 30 seconds, while for others it may take about 20 minutes.

The shaving and cutting is the most difficult part, he says. With even one small careless scratch, the whole skin can be wasted.

"A sheepskin costs about 200 yuan ($32) each. The total cost of a bag can be over 400 yuan before it is ready for use," he says.

Hu Yongzhong, Zhang's fellow apprentice, says that in the old days, there were few cars or carriages on the roads, but almost every family would raise sheep, and so it did not require much money to construct a raft.

A sheepskin raft weighs about 12 kilograms and can be carried on the shoulder to cross the river instead of taking a detour across a bridge.

That's why these rafts became a major mode of transportation across the Yellow River. When going downstream, the raft ferries people; but going upstream, people have to carry the rafts on their shoulders.

"When sailing, sheepskins will be on the river and people on the raft. Not even one drop of water will splash on your clothes," says Hu to tourists coming to ride the sheepskin rafts.