Resupply & water
Towns, caches, and where the next reliable water is.
Towns and boxes
Most long trails pass a town every 3–7 days. You carry 4–6 days of food at a time, send boxes ahead to the ones with nothing to buy, and resupply in the rest.
Water
desert cache or carry — plan every mile east filter from streams, easy high snowmelt, reliable in season report check the live water report
Why it matters
Water is the only planning mistake that can end a hike. A dry 30-mile stretch in July is a real problem if you didn't cache it.