Refers to a man-made water channel for drainage, irrigation, or sewage. Often used in technical or formal contexts.
A ditch is dug along the side of the road.
The canals in this area serve to carry rainwater to the river.
Compound of 溝 (ditch) and 渠 (channel). The exact historical derivation is uncertain, but the kanji combination is conventionally associated with man-made waterways.