sidguppy wrote:the location is Paraná River basin
any idea if this is really cold or subtropical?
The Parana river begins in tropical regions and flows south. It ends in the Rio de la Plata, where it meets the Rio Uruguay. This later river has a similar pattern, but leys more to the east
Said R de la Plata is at 35 degrees south - that is, in summer max average 22 C in winter min average 10 C
Due to the fact that bodies of weater - seas, that is - keep summers relatively cool and winters relatively warm, the Rio Parana (and Rio Uruguay) tend to be nearly the same temperature in winter for at least the last 800 km / 500 miles: further north the sun has more power (hotter) but the sea is further away (cooler)
Obviously, in summer these 2 factors both result in warmer water.
However, back to the Parana river - it is mostly sub-tropical