"Bravo" normally means that the river is running fast and furious over rapids or falls. The "blanco" obviously means smooth and clear, or clear and calm, before it picks up the red silt of further on downstream. The text is a bit literary, is it not?

I don't think rough collocates with river, (with sea yes), although we could try to turn it around and use rough in conjunction with water.

White refers to white water in the context of canoeing and other sports, and means lots of rapids etc: "The term "whitewater" also has a broader meaning, applying to any river or creek itself that has a significant number of rapids. The term is also used as an adjective describing boating on such rivers, such as whitewater canoeing or whitewater kayaking.." The term "whitewater" also has a broader meaning, applying to any river or creek itself that has a significant number of rapids. The term is also used as an adjective describing boating on such rivers, such as whitewater canoeing or whitewater kayaking..

*The river flows on towards Teruel with turbulence and white water* Not completely happy with how this reads, but maybe someone can knock it into shape!

I don't think we'll be able to keep the neat Spanish alliteration though.

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Note added at 35 mins (2010-06-02 10:10:32 GMT)
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Oh gosh, your further context has come in while I was writing - so it's not white water at all, but the colour as opposed to the red colour of the water later on. Ah well, my "gozo en un pozo"...

I don't think that rough is generally not used to refer to rivers, but rather seas. White-water covers the whole concept given that white-water foam is formed in rapids, where the gradient of a river is such that the speed creates trubulence that causes the water to be aerated. There are varying levels of white-water rapids in Kayaking and Rafting, 6 or up to 10 in fact, as you can see from the references. However white-water is not really used scientifically, and is used more in rafting. Rapids as a simple word contains the idea of rough and consequently white. That gets rid of the problem of referring to a river as white or rough...which sounds awwkward in my opinion. I hope that helps!

I think this might be a natural-sounding poetic option.