sambor rapids, Kratie province – Since the day they set their eyes on the Mekong river in the 19th century, the French hoped it would provide easy access to the riches of China’s interior.
It was here, their diaries show, they began to lose hope.
The rapids are not dramatic, but they were big enough to present a serious challenge to explorers lacking powerful engines or intimate knowledge of its rocks and eddys.
It took the first French explorers, traveling in 1866, three days to make the journey from Kratie town to Stung Treng town.
Today it takes more than seven hours in the dry season, and it seems like almost every kilometer is riddled with barely submerged rocks and trees.
Boats travel in such dramatic zigs-zags to avoid shoals that it can be difficult to tell if they are going upriver at all. Even with experienced captains and concrete channel markers, boats still run aground often, and passengers wait patiently as they are pushed off the banks by pole.
For the French, the shoals and islands were an obstacle on the road to riches. Today, the same view may be held by the Chinese, who are looking to revive the French dream of forging a navigation channel from Yunnan province to the South China Sea—a distance of some 2,500 km.
China is already funding a $5.3 million project to blast rapids, build dikes and remove shoals along the river from the China-Burma border to Ban Houayxai in Laos.
Little is known about how the project will be carried out. Officials at the Mekong River Commission, a multilateral agency formed to provide technical expertise on river development, have petitioned China for more information.
Meanwhile, fishery experts have begun to speak out on the importance of the rapids to the survival of a variety of fish populations on the river. Many of those experts will be meeting in Phnom Penh today at the NGO Forum’s second regional conference on fisheries in the Mekong basin.
The Sambor rapids are just one flashpoint of controversy. Today the rapids are mostly known as the habitat for the rare Irawaddy dolphins. Tourists board boats to observe the shy, elusive and still largely unstudied animals, which can live in both fresh and saltwater. There may be fewer than 200 dolphins left in the river.
During the dry season the dolphins live in deep pools just beneath the rapids, said Isabel Beasley, a biologist with the Wildlife Conservation Society. “Bomb blasts [for dynamiting the rapids] could kill dolphins very easily,” Beasley said. The channel “could cause the regional extinction of the population.”
Rapids act like a “natural water treatment system” in the river, said Council of Ministers Undersecretary of State Touch Seang Tana, who has studied the rapids fisheries. Water passing through rapids gains dissolved oxygen and sheds minerals. Fish need the dissolved oxygen to survive.
Much river life depends on sunlight, which can be blocked by blooming algae and plankton. Rapids force the algae and plankton to the bottom, where it turns into nutrients.
Fish typically use the deep pools just beneath the rapids as shelter from predators and fishermen, Touch Seang Tana said. In the early mornings and early evenings, they move to the rapids to feed and to absorb oxygen.
The rapids also play a key role in spawning, he said. As the fish struggle against rapids, the fat they accumulated during the feeding season is transformed into reproductive organs, a process aided by the clean, oxygen-rich rapids water. Many fish do not eat during the spawning season, living exclusively on oxygen.
Scaly fish lay their eggs in the sandy spaces between rocks, where water is warm and high in oxygen. Nonscaly fish deposit their eggs on the submerged portions of a tree species that flourishes near the rapids.
Destroying the rapids could extinguish fish species that live their entire life cycle near them, Touch Seang Tana said. Without the natural cleaning aided by rapids, the water will also be more subject to pollution from sewage or industrial sources.
The results may take a decade or more to show, Touch Seang Tana said. But the implications are worrying.
“The rapids are very special,” he said.