On a dusty mountaintop in Lesotho, Mamoliehi Tsapane beats sorghum with a wooden stick, the white grains popping from the husks over a bright green tarp.

Just beyond her backyard, a Chinese construction company is blasting the mountain, carving out the base of what next year will become the 73-metre-high Metolong Dam.

Commissioned by Lesotho, financed by Western and Arab agencies, and built by China's Sinohydro Corp, the dam is just one example of the international interest in capitalising on the crystal-clear water in this tiny mountain kingdom surrounded entirely by South Africa.

The building boom has generated billions of dollars in investment, but also changed the landscape and uprooted entire communities.

"I have no idea when or if we will be moved," said Tsapane.

"I wouldn't mind moving because we are close to the dam. I feel my life would be in danger. But at the same time, I feel like I have all this property here, and I doubt I would be compensated fairly."

Thousands of people have already been moved to make way for two dams over the last decade, part of a South African network of reservoirs and tunnels to divert water from Lesotho into the rivers that nourish Johannesburg.

The two countries are preparing to build the $993 million Polihali Dam to augment the system, with two more dams mooted.

The investment is equivalent to nearly half of Lesotho's national economy, and the construction is expected to boost economic growth by one third, from four percent in 2011 to 5.9 percent in 2013.

Last year Lesotho signed a separate deal with a South African construction company for a $15 billion water and energy project, financed by undisclosed Chinese firms. Work on the first phase is due to start later this year.

Most of the water and electricity produced will go to South Africa, which does not have enough of either.

Lesotho needs the money. Aside from some diamond mines and textile factories, the landlocked kingdom has no other exports. The dams are also expanding access to running water and electricity in a nation where these are luxuries.

The construction work also generates thousands of jobs, meeting a desperate need for work with an unemployment rate of over 40 percent.

But the dams call for complex compromises, at every level of society.

Tsapane has taken in workers at the dam site as tenants, each paying 100 maloti ($12) in rent, earning extra cash for her household -- until the water starts to rise. Then she may be forced to abandon her home and her crops.

"I'm worried about my fields. If I could know where I would be moved to, it would be easier," she said.

-- 'Life was better before' --

People already resettled have complained about the compensation scheme. They were given new homes, usually close to schools, clinics and power lines.

However, they are used to farming and herding and struggle in their new lives.

"My life was better before where I stayed," said Mampai Lesgapa, who was resettled for the Mohale Dam in 2002. "Now things are worse here because I have to buy on a daily basis and I don't have money."

At 62, she lives in a neat neighbourhood of cinder block homes in Ha Seoehlana village. The new homes are close to a main road, giving children a short walk to school.

They have electricity, which she can only afford a few times a month. But her family has no fields, forcing them to sharecrop for local landowners who take half the harvest.

She makes traditional brooms to earn cash, but now has to buy the grass that she once grew herself.

Under the agreement with the dam authority, the families could receive 2,000 maloti a year for 50 years to make up for lost crops.

Many here opted for a lump payout, which they used to start businesses, like a taxi service, said local councillor Lebohang Kolotsane.

"But you'd find if the car broke down, there was nothing to repair it (with)," so the business failed, he said.

Lucy Sekoboto, a lawyer with the Lesotho Highlands Water Commission, said lessons were learned from the first round of resettlements.

"Sometimes it's not easy to please people 100 percent. People were compensated," she said, but added: "If they find life difficult here and there, they start blaming the project. That's why I'm saying you'll never get rid of that, it's natural for people."

The commission says changes have been made to the compensation programme, including making payments ahead of resettlement to help families prepare for their new lives.

There has also been a clean-up in management. The first phase of the South African dam project resulted in convictions of some of the world's largest engineering firms, after massive corruption was uncovered in 1999.

More than 12 multinational firms and consortiums were found to have bribed the chief executive of the project, Masupha Sole, who served nine years in prison.

Metolong is different from the other dams. Its main purpose is to provide water and electricity to people in Lesotho.

Even those benefiting most directly are worried about the social cost.

"The dams are good for us because we are able to get jobs," said Michael Lenka, 51, a mechanic at Metolong.

"It's better if they don't move, it's better here," he said over the din of bulldozers and dump trucks, looking at Tsapane's quiet home.