<blockquote class=quoteheader>The bad one wrote (
see)</blockquote><blockquote class=quote>
Tony Thermoclines don't happen on running water and on deep stillwaters (waters over 20 ft deep) where they do happen, they only occur in the summer months.
I can see the logic of your thinking re river and weirs but it's not totally correct.River temperatures are acomplexmatter, but as a rule of thumb, they are more or less the same temperature from the the upper midsection down to the estuary. The upper zone on the hills, the temperature will generally be colder that the mid section simply because the hills are a colder place for much of the yearthan the lowlands.There may be a short period of time during the high summer when the two are equal. And that is only likely where the head of the river leaches out of bogland. If the headof the river starts from a deepunderground aquifer the waterleaving it is going to be much colder (between 42 -50 F) than the surface source head.
In the winter the opposite is true. The aquifer water is still between 42-50F, as the water temperature in aquifers doesn't vary much, a couple of degrees F at most. But the bog water may be nearfreezing, 34-38 F,for much of the winter.
By now you kinda get the picture of the complexity of it and I've not even factored in warm and coldrain, heat island effects of discharges from towns and cities, other discharges from lakes, reservoirs and so on.</blockquote>
Ther's always a danger of making a tw*t of yourself when you start discussing things that you have little knowledge of!
I don't mind though because I now understand a little bit more about the river than I did before, thanks to your excellent reponse Bad One/forum/smilies/smile_smiley.gif(the moral of this is don't be afraid to ask stupid questions!!/forum/smilies/wink_smiley.gif)
Still need to understand more about the effects of environmental factors on fish, particularly with respect to locating them and their propensity to feed.
Anyone know of any good reading or articles online that deal with this important aspect of angling?