open channel; open conduit
Technical term in hydraulics and civil engineering for a waterway with a free surface exposed to the atmosphere, such as a canal, flume, or drainage ditch.
Manning's formula is often used to calculate the flow rate in an open channel.
Open channels are used for irrigation in this area.
水路 is a general term for waterway or channel, while 開水路 specifically refers to an open channel as opposed to a closed pipe or tunnel.
Compound of 開 (open) + 水路 (waterway, channel).