tributaries
n. countable B2 Upper Intermediate US //ˈtɹɪbjəˌtɛɹiz// UK //tɹˈɪbjuːtəɹiz// trib·u·taries
n. smaller rivers or streams that flow into a larger river. They join the main river to help it grow bigger as it moves toward the sea.
n. streams or rivers that flow into a larger main stem or a lake. They do not flow directly into the ocean or sea.
The Missouri River is one of the largest tributaries of the Mississippi.
Heavy rainfall in the mountains caused several small tributaries to overflow, eventually flooding the main river valley.
The health of the entire river system depends on the water quality of its various tributaries, as pollutants upstream eventually accumulate in the primary channel.
Usage
Often used in the plural when discussing geography or drainage basins.