What is the name of this outlet used to drain water from ponds and ditches to irrigate farmland?

Channels in architecture refer to artificial waterways with free water surface. Most of the channels on the ground are open channels. Buried in the ground and enclosed around it is called a culvert (see water pipeline). Channels can be divided into irrigation channels, power generation channels (for water diversion and power generation), water supply channels, navigation channels and drainage channels (for eliminating farmland waterlogging, wastewater and urban sewage). In practical engineering, one canal is multi-purpose, such as irrigation, shipping, water supply, irrigation and power generation. The main contents of channel design include: the selection of channel route, the determination of section form and size, and the formulation of channel seepage control measures.