On Apr 25, 10:35*pm, DaveS wrote:
On Apr 25, 5:03*pm, notbob wrote:

I'm about 100ft from river (hypontenuse) and the early bird population is
going crazy. *Saw a BWO on my window so I figure that's the hatch. *My
question is, why do the birds fly so high, about 100-200ft above river.
None down next to river. *Do mayflies go high after emerge?

nb

What is the wind doing? is it am or late pm? Is the incoming wind much
warmer or colder than the water temp? Its got to be the wind and the
swallows at least just go where the food is.

Dave

Here in the West, particularly on the dry side, air (wind) tends to
move up and down the river valleys as hotter (or cooler) air from one
valley, flows into another valley at a lower or higher elevation,
propelled by the need to equalize the temps, one valley to the next in
the chain of valleys that mark the course of these western Rivers. As
this new wind develops, most often towards the late afternoon and
early evening, it flows over the river water which is generally
colder, and tends to lift the insects upward as the warm air is
lighter than the cooler air. Maybe that is why the flying caddis are
more bird food while the fish are keyed into the caddis that are still
in the hatching process?

Narrowing of valleys at exit canyons, and on a much larger scale, gaps
in mountain chains create some amazing wind energy opportunities. For
example the winds in the lower Columbia Gorge = a windsurfing
paradise, and much further inland over 450 turbines produce a max of
300 megawatts at the Stateline project south of Walla Walla. But the
winds blasting thru the Stampede Pass gap in the Cascades have a max
output of 230 megawatts (power for about 75k homes) from only about
130 turbines on the Wildhorse project East of Ellensburg.. These mega
flows of air complicate the valley to valley flow stuff.

Anyway, as near as I understand it, thats what I think happens. There
is a great new book out on weather entitled "The Weather of the
Pacific Northwest," by Cliff Mass, Uof W press. which I am presently
trying to understand.

Dave