I am so glad that you loved this wonderland. It means a lot when people read and respond to your travel memories.

Is this river created by melting snow or does it have a source in the ground?

It is created by melting snow. I have posted the glacial lake on the post linked at the bottom of this post.

Did you have any steep ascents on the way?

The first day was a bit steep but this is an easy route and its straight and easy most of the time. We did it pre-season, so weather made it a bit difficult for us. But it is definitely an easy trek.

can imagine there is no other way to transport goods there than by using the animals?

There are helipads but helicopters are too expensive to carry everything. And of course, these are trails and not actual roadways.