I did the first 164 miles last year and I'd consider last year to be a pretty weak winter. Even so, water was very reliable at a lot of the more questionable water spots. I never actually felt like I needed more than 4-5 liters. With the snow they've been getting this season, I'd expect much of the same. However, there are some sections where caching water is recommended, such as between Oracle and Superior, and Flagstaff and the GC, which I plan on doing.