The ultimate fighting machine runs on water, and dehydration sky rockets when soldiers are forced to fight or labour in body armour. That the Roman soldier carried water, or that water would need to be carried for him, is beyond question.
Unfortunately evidence for the personal carriage of water is not obvious in our era. Contemporary military sculpture does not give any clear hints.
Some re-enactors choose to use metal containers as these are robust and have been found on Roman sites in Northern Europe. However, we have been unable to provenance such items before the third century AD, and may have been used for oil, not water.
Given its light weight, leather seems to be a good alternative. Several fragments of leather water skins have been found at Roman period sites in Egypt, some of which have early military associations. Interestingly, many of these leather fragments are made from simple intact goatskins, and similar types are still in use in the developing world today. This raises the question as to whether the hide shaped bag on Trajan’s column was intended by the sculptor to represent a water skin. This is at variance with Fuentes’ interpretation that water was carried within a container in the net bag. The reconstruction of just such a water skin, based on fragments from Egypt and Israel, is likely to be a future project for us.