As someone who has primarily car/canoe camped, its never been too big of an issue for me to bring any water i may need. with backpacking, i would imagine packing water wouldnt be practical, so im guessing finding and filtering water on the trail is my best bet.

aside from obvious contaminators, like upstream farms/livestock ranches, is it safe to assume that water from natural sources can be filtered and drank? should i avoid lakes/reservoirs and go for rivers/streams? should i boil in addition to filtering?

the area ill likely be hiking in this spring, on the east side of the cascades, is full of rivers and streams, fed by melting snow i believe. it sounds pretty clean to me, but any advice would be greatly appreciated, thanks!