Snow accumulates fresh water at high altitudes, then releases it at an opportune time (spring) in large yet tempered rates. If you can’t pump water up, nor have good low altitude sources of it, build your farm up near the snowpack and build terraces & irrigation to take advantage of timely runoff of fresh clean water. The higher the farm plot, the greater the volume and quality of water available, as mountain peaks concentrate the snow in relatively small areas.
I remember reports from the Donner Party regarding such novel survival methods.