Flow rates and Thames conditions

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alanch

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The flow rate shown on the Maidenhead rowing club website shows that the flow rate has been decreasing for the past 4 days. Yet on the EA thames conditions website it has shown caution stream increasing for the same period from Boulters to Bray. Anyone know why they are different? I depend on this info to decide when to take my low powered boat out.
 
Could be as simple as the rowers are there every day whereas the EA gizmo is remote?
A few times last winter B1 reported flow rates increasing/decreasing and this didn't correspond with what we were seeing riverside maidenhead.
 
Flow rate at Maidenhead Bridge is a single point measurement. Maidenhead is also within the area served by the Jubilee River so, if the JR is being employed to relieve the main river the flow between Boulters and Romney will be very different to flow above and below that stretch. If the JR was being shut in then I would expect that to increase the flow rate at Maidenhead. I certainly don't think it likely that there was any adjustments being made to favour Henley, which is still weeks away yet anyway !

I don't pretend to fully understand the workings but I would say that the Yellow and Red board warnings are more useful to us boaters than a single point flow rate measurement. I only regard the flow rate readings as an indicator of rate of change and how much water is coming down the river.

We ran down from Penton Hook to Hampton Court on Saturday with Yellow Increasing and it made for a swift journey with, perhaps, a couple of knots of current assisting us down river. The strength of the weir stream below Shepperton Lock was certainly noticeable as the flow swept round towards the Desborough Cut and arriving at Hampton Court called for some focussed thinking when mooring as, head to, the bow was quickly caught and swung out by the current. Several NB's had a difficult time turning, and without enough power to react quickly in the same way that I could with a lighter craft and twin shafts.

Coming back upriver on Sunday things were calming down but probably still around a knot and a half so slower progress but little to worry about as long as you allowed for offsetting if crossing weir streams such as entering Penton Hook marina.

You mention having a low powered boat - how low powered exactly? I tend to err on the side of caution and would not go out on Red Boards or on yellows if the forecast was worsening. Last Saturday was actually quite a rare experience for us in that I cannot remember having previously set off with Yellow Increasing boards out, but it was a good call and the weather generally made for an enjoyable weekend.
 
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You mention having a low powered boat - how low powered exactly? I tend to err on the side of caution and would not go out on Red Boards or on yellows if the forecast was worsening. Last Saturday was actually quite a rare experience for us in that I cannot remember having previously set off with Yellow Increasing boards out, but it was a good call and the weather generally made for an enjoyable weekend.[/QUOTE]

The boat is 30ft by 12ft with a 38hp hydraulic drive and good for 6 kts. Because of its low power I don't go out on reds or yellow increasing, but am quite happy to go on yellow decreasing. I went out on Sunday from Shepperton to just above Chertsey lock and back having seen that the flow was ok having decreased considerably at Maidenhead quite a bit over the previous few days. Probably wrong on my part to use that as a guide so much further downriver, although having been around the area since Thursday I judged that the flow was decreasing not increasing so went out and did not have any problems. Then again I am well acquainted with going sideways on the water!
 
"Dumping water so the river can be slowed down for HRR?"

"Doesn't work like that."

I think we had this conversation some years ago on the Forum!
 
Just a thought, but does "yellow, stream increasing" actually mean: "stream increasing, or steady at a higher rate than normal, but not actually decreasing!"?

The boards from Boveney to Marsh appear to have been 'Yellow Increasing' for quite some time (if I'm not mistaken). If actually increasing all this time, you would have thought they'd be Red by now ;)
 
thames cruiser said:
Just a thought, but does "yellow, stream increasing" actually mean: "stream increasing, or steady at a higher rate than normal, but not actually decreasing!"?

The boards from Boveney to Marsh appear to have been 'Yellow Increasing' for quite some time (if I'm not mistaken). If actually increasing all this time, you would have thought they'd be Red by now ;)
Click to expand...

Doesn't the whole thing about red and yellow boards relate to how many weir gates have been pulled? If they are stilling pulling them then it is increasing, it's only when they start putting them back in that the sign would change to decreasing. I'm sure I learned all this from Teddington Lock and Shades via this forum. but of course I could have totally misunderstood them :)
 
That's completely right. :)

However , it does rely on the message that they are shutting in getting to the people who update the website.

If in doubt , the lock is only a phone call away.
 
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