The stream's catchment.
Drainage Basin
it sounds like a drainage basin
The area a stream gets heat from is generally the part moving slowest allowing it to be heated by the sun.
it gets water from the rain and the ocean
The velocity of the water in a stream increases when the stream gets narrower or shallower (or both).
An effluent stream receives water from the banks surrounding it and so gets bigger as it goes along. An influent stream donates water to the banks around it and so gets smaller as it goes along (think desert conditions)
A 'floodplain'.
a stream gets wider when it gets older and the water erodes the bed of the river to make it wider
A zebra gets water from a river, or stream.
The flood plain
the gulf stream gets its warmth from the tropics
Energy that water gets from the sun is most commonly absorbed in the form of heat.