A little while ago, in response to a query on a kayaking forum that I`m a member of, I posted the following information about the Water of Ruchill. There was quite a lot of information in my post, so it may be useful to a wider audience.
I have also added a bit more information in this webpage.
I ran the Water of Ruchill a few times, about 15 or so years ago, so have some vague memories about it.
First off, you need a LOT of rain to get the level up enough to run the upper half of the river, which is continuous boulder river, with a pretty continuous gradient. If the road up the glen is totally awash, then the river will probably be high enough.
If the level of the river is up enough that you aren`t scraping down the first half of the river, then the falls are a very serious undertaking - inspection is an absolute must.
Get out river left quite a bit above the falls - the closer you are to the falls, the more difficult it is to get off the river. If you leave it too late, you`ll get funnelled into the falls.
Do not under estimate the importance of this - if you run the first drop, you are taken down into a gorge - there is no escape from this gorge except down river over the next two drops. You cannot climb out. I know of somebody who had to be pulled out of the gorge on ropes, because there was no way he could run the other two drops.
Inspect and portage from the left bank.
My recollection is that all three drops are nasty at high levels - the first one is a steep ramp, the second one I can`t remember, and the third one is quite a problem. I think ( vaguely ) that at lower levels, there is a sneak route hard left on the third drop, but at higher levels this is a no-no, and the only possible way down would be very hard right - which is quite difficult to get to - you`re going to have to paddle right round between the cliffs and the drop - not for the faint-hearted.
We did run the falls once, probably we scraped our way all down the first half of the river. At higher levels we portaged the falls.
I can`t remember anything about the next bit of the river, which probably means it is a non-event. However there is another significant rapid quite a bit further down - it is nothing like the falls - it is a long rather broken and rocky ramp - I guess a grade 4. I recommend inspection of this as well, again, inspect and portage from the left bank. As far as I can remember, the best route is a bit right of centre, but there is a bit of a sting in the tail of the rapid.
If my memory serves correctly, that rapid is the last feature on the river, and the run from there down to Comrie is very tedious and boring, even when the river is high.
Much better to get off just after the last rapid - if you are coming from Perth, drive through Comrie, just before you leave the village, there is a road on your left, which goes over a stone bridge over the Earn. Take that road, and bear left at the junction. After a long straight, the road joins the river, and after some bends, there is a car park beside the river. Park up there - the last rapid is just upstream of there.
The Water of Ruchill isn`t the most wonderful river to paddle - if the level is low, you scrape all the way down the boulder section, but can do the falls. If the level is high, the boulder run is somewhat featureless for much of its length, just continuous, and then you will probably portage the falls. However it makes a change from the usual rivers.
The Water of Ruchill is not suitable for beginners. If someone takes a swim coming down the upper section, you would have a difficult time getting them and their boat out before the falls.
I hope this is helpful, however don`t rely on it too much, as it was a long time ago. Go read the SCA Scottish River Guide for more information.