nawang norbu is the director of the school for field studies bhutan program. >> and what country is building do the indians build it and then get the power to pay it? >> they get the power. >> we sell it to them, and then we sort of liquidate the loans away. we have five such dams which are operational. >> five. >> and i think six being constructed at the moment. you know, obviously there's a lot of destruction. it will stop some of the fishes from migrating up and down. you're also talking about a lot of transmission lines. but obviously for bhutan, i think when we started on the path of development, i think we were left with few other options, and i think this was the best thing for us to do. >> the water that comes through this dam, is it an inexhaustible supply? >> it's all glacial water. >> we hope so. there are many studies which are showing that the himalayan glaciers will disappear in about 50 to 60 years. >> whoa, whoa, whoa. that's soon. >> yeah. >> yeah, but nobody knows for sure. i mean, the science is debatable. >> are we talking about the difference between 50 years and 100 yea