That sucks that you can't get reliable electricity. Most people take such things for granted. Anyway, expanding on what others have said, hydro
electric developments are often massive programs that require great expense, long times and extensive infrastructure.
That being said, it doesn't necessarily mean you can't do it. There is micro hydro which may be a viable alternative, in terms of cost, labour and
materials, especially since your country is rather mountainous, what with Everest and all.
Also, reading up on wiki, it says your country's closest sea port is Calcutta, India, which is a fair way away, to say the least. Add to that a poor
road infrastructure and the costs begin to climb on a major project. Especially, if you have to get materials manufactured overseas.
I think the best thing would be to start small, get communities involved that do support the idea, get them up and running, so other communities can
directly see the benefits of small scale electricity production. It's possible your government may be willing to support smaller grass roots projects
like this, as it may not press on them as much to fix the other problems (such as roads etc) while providing a larger electricity grid without the
growing pains of a major project. I would try to sell it as a win win to the government, even if they may be a corrupt pack of..
You also have the downstream consumers of the water to think about. I did see a mention of dam-less hydro, as well. You must have plenty of wind
there, too. Has anyone looked into that for Nepal?
Anyway, you sure did scare the crappers out of the East India Company, back in the day, I reckon you could do this. Best of luck.