How water proof are these boots. I will be backpacking in the Colorado Mountians, will they hold up to stream crossings and keep my feet dry?

They are very waterproof. I've walked around in shallow streams to test this. Walking around in the snow is typically not a good test as these are not tall boots, and wearing gaitors with your boots doesn't always prevent water from snow from getting in there.. that being said these boots have been great to me even in the snow.

I walked with gaitors on in waist deep snow for several miles last winter, and my feet got soaked. I think brief exposure to very shallow water is OK, but don't expect to be able to stand in it with these boots.

They are made of waterproof fabric. That being said, your feet will inevitably get wet. between the stitchings, going over the boat, and in hot conditions, just sweat build up -- you can't stop the wetness from happening. If you are fording large rivers that goes above the middle of the tongue, your best bet would be to find a pair of quick drying socks and carry news paper to dry out the inside of your boots. The other options (the one I used when fording rivers along the Appalachian Trail in Maine) is to take the extra minute to stop and change into crocs. If the streams are really small and wont go up high, then you won't have too much to worry about, your feet will stay pretty dry.

GTX translates to Gore-Tex waterproof awesomeness. All encompassing dry feet.

they are totally waterproof