The availability of water in the rainforest is not usually a problem but the collection, storage and purication of it needs careful thought. It is often brackish so a filter should be used to remove particles. A chemical should then be employed to sterilize the water. Always have at least two bottles, one for drinking from and one for sterilizing so you never run out. A minimum of 2 litres should be with you at all times as you will need to drink a lot. A water bladder with drinking tube is extremely useful when trekking.