You need to be physically tough to work in Tsonyi county. It sits more than 5,000 meters above sea level in Nagqu prefecture of the Tibet autonomous region and the weather can be brutal.

At the Tsonyi county sub-branch of Agricultural Bank of China Ltd, only three of the 24 bank clerks are female. "Even the rocks in Tsonyi are male," Migmar Dradul, head of the Baingoin county sub-branch of the bank's regional office in Tibet, said.

Before he came to Baingoin in 2007, the 45-year-old worked as head of the Tsonyi county sub-branch for 10 years. He said the harsh environment there was too "hostile" for female employees.

"On the chilliest days in winter, the temperature drops to 20 degrees below zero. No one goes outside, except for dogs and crows," he added.

The weather is so extreme that offices and homes have to be heated 12 months of the year.

In the winter of 1997, the county was hit by heavy snow falls and Migmar Dradul and the rest of the bank staff went on a 300-kilometer drive to pick up cow droppings to use as fuel.

Later, they started ferrying coal from Lhasa, the capital of Tibet, to Tsonyi. "What's difficult for our staff is working when they are ill," he said.

Many suffer from high blood pressure, arthritis, stomach and heart diseases as well as memory lapses because of the altitude, bad weather and poor water quality.

But despite the problems, the sub-branch still provides financial services to more than 2,900 nomadic families in 31 villages. More than 80 percent of them are scattered across the county, which has an area of nearly 120,000 square kilometers－roughly bigger than the size of Portugal and Slovenia put together.

Some of the families are separated by more than 200 kilometers and certain villages lack paved roads. Bank officials are often left stranded after their cars get bogged down on dirt tracks as they drive to work.

On one occasion, the car carrying Migmar Dradul and his colleagues became stuck in the mud during a visit to the bank's operational office in Tsonyi.

Since there were no mobile phone masts in this rugged wilderness, they had to fend for themselves. Eventually, they ended up putting rocks under the wheels of the car to free it from the mud.

"It took us three days to get going again," he said.

For those families that live where there are no roads, bank officials visit them on horseback to agree loans or collect repayments.

"We usually send two staff together on a trip. They ride a maximum of 300 kilometers for two or three days, carrying a cashbox of more than 1 million yuan ($161,000)," Pug Tsering, 28, deputy head of Tsonyi county sub-branch, said.

The sub-branch has three operational offices, each sending employees to visit two villages a month on average.

"Our staff will notify the village chief a month before their visit and try to gather as many families as possible on a fixed date," Pug Tsering said. "For those who cannot be reached, the bank clerks will visit them one by one."

Winter is the best season to gather nomadic families together although the weather can be appalling.

Temperatures can dive to as low as 20 degrees below zero and snow storms are common. But during the summer, most of the herdsmen are grazing their livestock and are scattered across the region, so tracking them down can be difficult.

Families usually borrow money from the Agricultural Bank to buy grain, furniture and tents. They repay loans by selling livestock products, including milk tea, yak butter and cashmere.

By the end of last month, the Tsonyi county sub-branch had extended loans worth 691.49 million yuan, compared with 14.96 million yuan in July 1995.