Water rights and free speech are the latest sparks that have inflamed protests in Tibet against the Chinese government.

Hundreds of nomads -- yak herders and others whose way of life seems to exist outside of politics and time -- fought with police last month after a disagreement involving three teenage Tibetan monks and Chinese shopkeepers.

The incident, in Baikar (in Chinese, Baiga Shang), Nagchu Prefecture (China's Naqu Prefecture), ended with the monks being detained, and one severely beaten by police, witnesses told Radio Free Asia.

Afterward, nomads gathered outside to demand the monks' release.

The mob's numbers rose to almost 1,000 a day later, witnesses said, and soon began to grow violent, attacking government offices.

Hundreds of police were dispatched to the area, and an untold number of the rioters were detained.

Also in November, a Chinese court convicted a group of nomads and sentenced them to as much as 10 years after one of them called publicly for the return of the Dalai Lama, the exiled spiritual leader of Tibet.

All four tried to protest their trial, but were denied the chance to speak and escorted out of the courtroom by guards.

According to Radio Free Asia, a self-decribed "private nonprofit corporation," the nomads shouted, "This is not a fair trial, we cannot accept this decision."

Relatives of the nomads have appealed the decision.

Meanwhile, Tibetan exiles have charged China with causing serious environmental damage to the Himalayas, the highest mountain range in the world, and the source of the most important rivers in Asia.

According to the United Nations, half the population of the planet gets its water from rivers that originate in the Himalayas.

According to a report by the Tibetan government-in-exile, Chinese hydroelectric projects will cause reduced water supplies in India, Bangladesh and even Vietnam.

The government-in-exile charges that these projects are designed to provide power to Chinese cities, but contribute nothing to Tibet.

The Chinese government has been reluctant to acknowledge environmental concerns in the region, but the issue is being openly discussed in China, according to the U.S.-based International Campaign for Tibet.

"From a central level, there's intransigence," the group's spokeswoman Kate Saunders told the U.S. government-funded Voice of America, "but on different levels, multiple levels of Chinese society, it's still possible to make some headway and have some discussion on environment."