in the caravan menu (when in town) it tells you your water consumption per day (example 10 litres per day) and your speed (e.g. 6 km/per hour) times the speed by 24 (6 x 24 = 144 km/ per day)
now go to the map and draw the line between location and destination this will tell you the distance (e.g. 288km away) so this trip would take you 2 days so 2 days of 10 litres per day is 20 litres same applies to food and forage
its wonderful and rubbish at the same time im deeply confused the graphics look terrible at first glance but look closly and there fantastic its weird ill give it 5/5 just to make my brain stop hurting