The start
The oxygen content of a river or stream is likely to be highest at the source. The source of the river or stream is where it originates.
The source
The source of a stream is called a headwater or headstream. This is where the stream initially begins, often from a spring or melting snow.
There are several streams that run quite close to Tauranga CBD. For example the Waimapu Stream and Kopurererua Stream. Strictly speaking though, the closest RIVER is Wairoa River.
The source
headwaters
The "Gulf Stream".
The hottest part of the oven when baking a cake is usually the top heating element or the top rack closest to the heat source.
The strongest part of a magnetic field is typically closest to the magnet or electrical current creating it, while the weakest part is farther away from the source. Magnetic field strength decreases with distance from the source due to the inverse square law.
The Gulf stream
The O2 sensors that are the closest to the engine will be the up stream ones. The ones that are further away from the engine are the down stream sensors.
It beagins from a spring or source