To reply to Nigel H:
I carry two 10 litre Ortlieb water bladders in the boat, though I don't fill them completely. The amount I carry depends on the plan for the days ahead.
I can't say how much I drink as I haven't been monitoring it on this one, but on the records I plan on about 400ml per hour - this varies with intensity, weather etc. I don't think it is enough but I find it difficult to take in more, especially when it's cold.
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