The term 'Millstream Channel' refers to a SLUICE, which is a waterway or channel that is used to control the flow of water. It is typically used to divert water from one area to another, such as from a river to a millpond. The SLUICE is usually made up of a series of gates or valves that can be opened and closed to regulate the amount of water flowing through it. Millstream Channels are often used to power waterwheels, which in turn can be used to generate electricity or to power machinery.