yes you can, keeping in mind the need to create proper dams and seals.
would it be possible for me to create hillsides and move the earth to whatever position or shape I want?
the small slopes I do see are north facing.
ok. no worries.
I have no problem with installing water pumps and moving the land I will put the effort in and do the work if need be.
You might want to choose species that do not require such a fast flow. I'm thinking that you might be considering arctic char, which are not the easiest fish from my own studies. I don't mean to sound weird about it, and correct me if I'm wrong, but I'm thinking that you have no experience whatsoever in fish farming, or developing land, so I'm going to say that you are going to have to ask a lot more questions if you are wanting to avoid either a catastrophic failure of your system, or a vast waste of money and time on a system that does not perform the way you want it to. Considering that you clearly have some income that you can put to the task, you might want to hire a consultant who specializes in such things-at least for your water system/pond infrastructure.
Also I can't seem to find water pumps that can pump a high enough volume of water to create artficial stream like systems and also what about soil erosion due to faster flowing water? What about tree roots hitting the river bed and causing leakage?