The term 'dams up' refers to the act of blocking or obstructing the flow of water in a river or a stream, leading to the formation of a dam or a barrier. The antonyms for this word would include phrases like 'opens up', 'lets flow', or 'releases'. These words imply the opposite of holding back and are associated with the free movement and circulation of water. Other antonyms for 'dams up' include 'frees', 'unblocks', 'disperses', and 'unleashes'. With their connotations of openness and fluidity, these words help to paint a picture of a river or stream flowing naturally and unimpeded, without any human intervention.