Well, I can give you only first hand information of being there for about 2 years and information of the locals there.TwoTankAmin wrote: 17 Nov 2017, 16:45 @Walter
The information I have read indicated that the onset of the rainy season for the central Brazil region usually starts between Sept and Nov. So I thought perhaps this was the time the water levels in the Big Bend should be rising. Since the official posture is that water levels will be maintained at peak dry season levels year round, I was looking for confirmation from somebody actually there that the normal rise was not happening or that this info was wrong a water levels were indeed rising. Please keep us posted.
I also always had problems to determine high- and lowwater seasons and rainy seasons in the Amazon basin (e.g. using the Smithonian Atlas of the Amazon).
I have always been told, that seasons differ within the Amazon area widely, and every year is different.
My own experience: September seems to be the best month for (ornamental) fishing/diving nearly everywhere in central Amazonia, or let's say August - December. Lowest water levels do not necessarily mean best time, because it is hard or even impossible to go to some places (e.g. Rio Negro Igarapes/tributaries) by boad, because of low levels.
This "September is best" own experience is valid for lower Negro river, central Solimoes river, Tapajos, Xingu, Araguaia, Purus (maybe November).
Lowest water levels probably October - December (depending of start of rains), normal "rainy season" starts around Christmas, rising levels up to April, May, ...
High water means also turbid water (concerning clearwater rivers and also blackwater tributaries to Negro), won't mostly see much underwater.
Low water means clearwater. But this clearwater is not that "crystal clear" as someone may think, as e.g. some Cenotes in Mexico show, or Alpine lakes here in Austria. Snorkeling here in Austria in Danube river (Neue Donau) under good weather conditions I have probably a better visibility than in Xingu or Tapajos. This was a big surprise for me (when I came to those clearwater Amazon tributaries for the first time).
Do not have any experience in Amazon waters of the Andes... so it may be different there.
Walter