Thailand, too, has dammed the main tributaries that flow across its territory.

ECONOMIST: The Mekong river

Interest is kept with subplots that intersect with the main one, like tributaries of a river.

FORBES: Fact and Comment

One is an immediate effect as surface run-off takes roughly 50% of the free nitrate straight into Thames tributaries and the main river.

BBC: Thames archive reveals long nitrate rise