all be it that the rivers come from differant sources, if the river tame water temp was 4.5 degrees in stockport, do you think the river goyt running in a similar direction to stockport would be the same/similar temp?

Good point Jerry, Ive not been doing temps readings for long and not that often but in this cold weather the goyt has always been 1c+ higher than the tame, they will be reasons for this, maybe water surface exposure area.

I know that tree coverage will insulate the ground area under the tree canopy by 3 - 5c, I see this all the time when doing thermal surveys outside.

You can see in this image that the goyt has a lot more tree coverage along its path than the river tame.

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There are other points to consider of course.

Firstly Glenn, do your tree cover surveys mainly deal with large fully forested areas, and over land rather than over water? A river, even with bankside tree cover, still has a lot of water exposed to the air. How far from a forest edge will that 3-5 degrees extend? Not far I suspect, even in still air. And were your trees in full leaf at the time of survey?

Still air will affect things, as will windy conditions. You need to determine the temperature difference across the air water interface. And I suspect that, because hot (warmer) air rises, that a river will cool down quicker than it increases in temperature, when comparing the same +/- x degrees difference across that interface.

The average depth will have an effect, a shallow river cools and warms at a higher rate, than does a deeper one.

The most important effect is likely to come from the geography of the river, how much of it flows through higher, and therefore colder terrain. Higher ground in winter will also contribute more snowmelt water to the river. Melting snow running into the river will have exactly the same effect as rain at zero degrees, the high "latent cold" of snow having already dissipated into the air, before the melt hits the river. But snowmelt is still a source of very cold water into the river, and it is almost guaranteed to be colder than rain.

All in all I suspect this is something which cannot simply be calculated or guessed at. I think you would need, over a period of some time, to sample water temps daily at a location like Watersmeet, with a thermometer and a long piece of string, or a small sampling bucket. Only by doing that would I think any yearly pattern would emerge, from which conclusions might then be drawn. I suspect that any perceived higher temperatures in one river, might well reverse later in the year.

Early this morning as I walked the bank (without tackle) I measured a temperature of 3.4 in the water. But the water was visibly steaming, suggesting strongly that it was getting even colder.
I was getting colder too. ;-(

Apologies to all, I do tend to get a bit technical at times.

Its very true that you have to factor everything in but in general I would still put my money on the exposure effect.

Im very sure that if the tame was heavily lined with trees and sat in more sheltered valleys (geography) as the goyt does it would be warmer river.

The insulating effect can be seen under singular trees

I dont survey trees but I do have a thermal image of this effect, just have to did it out

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I would have thought that with the Goyt starting 200 mts higher than that off the Tame it would have some bearings on the winter temp??

Barrie

Probably has some effect, but remember the uppermost stretches contribute only a small percentage of the river flow at the points where we usually fish.

How quickly do you think the river can absorb higher ambient temperatures.

Looking at my river tame readings I think the rise happens quite quickly.

Edit: talking of low temps read this news report http://www.dailymail.co.uk/news/arti...l-COOLING.html

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I think rivers warm up a fair bit quicker than do stillwaters. A fair bit of the water is run off from the land, and hence there is much more surface area to absorb the heat from the atmosphere. Especially so if direct sunlight can hit any of the small input streams and their catchments.

Consequently they also probably cool down quicker too.


On the article: I really do not know why one blip, one low temperature year is so seriously considered as a trend, rather than a statistic, by so many people.
These people could be right, but I very much doubt it. This winter has merely been one in which I didn't get my fair share of global warming.
I do however consider that the theory of global warming shifting the warm ocean Gulf Stream around, and not to our benefit, is one that might be noteworthy. So I am not discarding the thermals just yet.

I saw a TV doc about how how all this melt water from the north pole is strengthening the Labrador current and how it might redirect gulf stream, the very same system that gives us mild weather. If this goes south then we'll see real winters like Moscow daily winter temps of -25c the norm

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Just great morning temps of -8 or -9 and the ball and chain says I can't go fishing on mothers day? Your my wife not my F***ing mum
Im still going

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