The Mekong River shows surprising signs of health, but officials from the regional Mekong River Commission (MRC) warned that a lack of available data meant trouble could be lurking beneath the surface. That was the finding in the MRC's first State of the Basin Report, which was released on August 27.

"As far as it looks today, there is no reason to ring the alarm bells," said MRC chief executive Joern Kristensen. "You have a pristine river compared to other rivers in the world."

However the MRC's scientists said more research was necessary in order to understand the river's ecology and the effects it has on Cambodia, Laos, Burma, Vietnam and Thailand.

Earlier this year, the MRC launched the first long-term studies to provide a comprehensive assessment of the ecological health of the river. Initial results surprised researchers.

"The changes we found in the river were not the ones we expected to find," said Ian Campbell, a river ecologist at MRC. "We need to spend more time to work out the implications."

The research indicates that the average water flows in the Mekong in recent decades have risen during the dry season and fallen during the wet season-a potential boon for farmers, fishermen and those living in flood-prone areas. Additionally, expected increases in river-borne silt and saline levels have not materialized despite rapid deforestation and development.

The scientists said that was likely due to the more than 20,000 small irrigation works built on the river and its tributaries. The small dams and levies moderate extremes in seasonal water flow and catch silt headed downstream. The report also put to rest rumors that the Tonle Sap will fill up with silt by the next century. MRC estimates that at present rates the process will take at least another 10,000 years.

The report highlighted the growing importance of fisheries and wetlands under threat by development. The population in the Lower Mekong Basin is expected to grow from 55 million today to 90 million in 2025. Fisheries in particular will bear the strain of feeding millions of people who rely on fish for their protein. The river already provides an annual harvest of two million metric tons of fish worth $1.4 billion.

And although the total catch in Cambodia has almost doubled since the middle of the century, individual fisherman now catch just half of what they once did. A typical haul today consists of fish with one or two-year life cycles rather than longer-living species that, at least in the case of the giant Mekong catfish, have been nearly wiped out.

The report also stressed that the use of pesticides and the presence of toxins such as heavy metals are a long-term concern for fisheries. The use of agricultural chemicals in Thailand has already forced that country to import some species from less polluted countries such as Cambodia. A cascade of dams to be built on the upper reaches of the Mekong in China also threatens the river's health.

Campbell said governments needed quality information to help them understand the problems and effectively deal with them.

"The biggest issue is how the water is used, where it is used and what it is used for," he said.