The are some concepts around rivers that are not necessarily intuitive- 1. When rain infiltrates into the soil and downward into aquifers that helps river flow year round. Wet season rain can come out (in the river) during dry season because water traveling underground moves very slowly. So activities like digging swales can get rivers running year round again, as swales help guide rainfall undeground.
On rivers, floodplains, vegetation, and climate
Thank you, Alpha.