The term LOW DAM OVER A STREAM can be solved by the four-letter word WEIR. A WEIR is a man-made structure that is built across a river or stream to control the flow of water. It is usually made of concrete or stone and is designed to raise the water level, forming a shallow pool upstream. The purpose of a WEIR is to regulate the flow of water, reduce flooding, and provide a source of water for irrigation and other uses.