In reply to Stephen Reid - Needle Sports:
Interesting and sounds about right for lower level fast flowing water falls. Of course Udlaidh forms from springs not fast flowing streams/rivers and is higher up the hill. Generally as you go up higher the temperature fluctuates less during cold snaps than lower down in the glens,when the day time temperature may be closer to zero but the night time temps can be much colder than on the tops.
I've found in the past even when it's been -10 to -20 during sustained very cold snaps (here and abroad) there is still normally water flowing over the ice in places (and for most proper water ice there will usually be behind IMO)
I have read for Udlaidh if its really cold the springs can freeze at source and then it won't form properly, but that didn't happen during the 09/10 10/11 winters that were properly baltic for fairly sustained periods.
Post edited at 23:00