How many dams are in the Mekong River have?

Mekong River Dams Ruin Livelihoods of 65 Million -- 11 More Are Planned

17 dams recently built on the Mekong River in Southeast Asia are threatening fisheries, destroying a vast ecosystem, and starving millions. And 11 more dams are currently in the planning process.

 

The dams already in place are blocking fish from traveling upstream to spawn, and the new dams-- many of which will sit nearer the river's headwaters-- could threaten the entire river ecosystem. 65 million people currently live and rely upon the Mekong for their sustenance and livelihood, and about 80 percent of their protein intake comes from the river's fisheries.

The Mekong is Southeast Asia's largest river, and it flows over a vast distance-- from China to Myanmar (Burma), Laos, Thailand, Cambodia and Vietnam. The totality of the river's basin is one of the world's biodiversity hotspots, and it provides a habitat for over 1,300 species of fish. In fact, no other river is home to as many species of very large fish, such as giant river carps, giant catfish and massive freshwater stingrays. But the dams could change that forever.
Most of the new development is slated to happen within China's border, which will effect the entire river system downstream. That development is already undermining fish populations and causing erosion in Myanmar, northern Thailand and northern Laos.
Aside from harming fisheries, the dams are putting millions out of work who make and sell products from the river, including jobs like repairing boats and making fishing gear. Furthermore, thousands are set to be displaced. The controversial Nam Theun 2 Dam project alone will flood more than 600 square km, and will displace at least 7,000 when completed.
Meanwhile, victims of the dams and displacement are often promised compensation which they never properly receive, or which is hardly enough. For instance, in China two resettled communities have seen lower fish catches as well as an increased incidence in disease, both long and short term consequences which are hardly treatable with the compensation they got, according to the group International Rivers. That's just one example of what is happening all across the river system.
Of course, the region's growing electricity needs are often cited for the necessity of building more dams. It's true that the dams already in place along the Mekong provide much needed renewable power to millions. Though there is certainly a point when enough becomes enough. Too many dams end up harming far more people than they help, and in immeasurable ways that aren't sustainable.
If you're interested in learning more and doing something about it, one of many groups you should contact/donate to is International Rivers.