Meeting of the Waters

Below Manaus the Rio Negro joins the Solimoes to form the Amazon proper, and for something like six kilometres the two run side by side in the same channel without blending - the Negro almost black with dissolved plant tannins, the Solimoes pale brown with Andean sediment, and a hard line between them that a boat can sit astride. Three things keep them apart: the Negro is warmer by a couple of degrees, it moves at roughly half the speed, and its density differs, so turbulent mixing takes kilometres rather than metres. Put a hand over each side and you feel the temperature step. It is the standard first excursion from Manaus and is usually combined with a run into flooded igapo forest and a stop at a stilt village.

What you actually see

• A hard line down the river - black and sandy water running side by side for kilometres.
• A temperature step - the Negro warmer than the Solimoes by a couple of degrees.
• The reason they resist mixing - different speed, temperature and density.
• Flooded igapo forest - the usual second half of the same boat trip.

When to go

All year; the contrast is sharpest at high water, roughly May to July. Half a day.

Honest expectations

It is a boat trip and the confluence itself takes minutes - the rest of the day is the padded-out tour. Operators vary a great deal in how much motoring and how much shopping they include. It is hot and shadeless on deck.

Nearby

Manaus and the Teatro Amazonas are upstream; the Anavilhanas archipelago is up the Negro.