How big of a stream?

[String&stick]

I've felt, read about, and heard on videos people talking about waterways effecting air currents. I've noticed this along streams in the 15-20ft wide range where the cold water seems to pull the air down stream for a little ways around the stream in effect fighting the thermals a bit in and around the stream.

My question is does anyone have a good rule for how much of a stream is needed to start having this effect or is it completely random based on slope, north or south facing, etc?

Just pondering elk while I should be working!

 

[Lark Bunting]

There is a natural seep on the hillside where I shot my bull in 2017. It's about 300 yards long and disappears back into the mountain. My bull happened to die in this little current of water that you could step across. The air temperature was easily 10 degrees cooler while processing the elk than it was a mere 20 yards away. I have no doubt it doesn't take much to impact thermals.

 

[IdahoElk]

More important to me is finding any running water combined with a draw or ravine that will hold the cooler air better giving you a little more time with thermals in both morning and evening.

 

[Sled]

I'm no weatherman but remember a few things from weather classes. Might be wrong but this is as I remember.

Evaporative cooling happens anywhere you have water. Running water accelerates that process. When you add moisture to the air it will be come cooler and more dense, both of which cause sinking. In the afternoon air gets warmer, less dense (lower RH) and rises. Thermals, diurnal or catabatic winds develop accordingly. The presence of a little running water will change that differently based on the amount of water passing by, current RH in the air and topography. A steep canyon wall will have less effect higher on it, especially as the sun hits it.

 

[NJDiverDan]

Evaporative cool is one of the causes, also, most of those seeps / springs are REALLY cold water. I agree that the smallest little trickle will cool off a canyon, especially if it is in a timbered area and basically create it's own thermal effects.

The more open the area, the faster the normal thermals will influence it. But some places I hunt, the bottom has its own wind that has nothing to due with time of the day.