What is the name of a man-made ditch used to collect rainwater?

The correct answer identifies irrigation channels as a type of man-made ditch designed to collect and direct rainwater. These channels are constructed to manage water flow, particularly in agricultural settings where excess rainwater needs to be diverted to ensure crops receive adequate water without flooding.

While both stormwater systems and drains can also serve to manage rainwater, their primary focus is often on directing excess water away to prevent flooding in built environments. Drains typically work in urban settings to collect runoff, but may not always be designed specifically for irrigation purposes. Water reservoirs are storage structures, not ditches, that hold water for various uses, including irrigation. Therefore, irrigation channels are the most accurate term for a man-made ditch intended for collecting rainwater, especially in agricultural contexts.