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Author Topic: Which river in Britain has the largest flow?  (Read 23212 times)

Offline P-Kasso2

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Which river in Britain has the largest flow?
« on: 01 October, 2010, 12:24:07 PM »
.
Dispute raged last night at the Brewer's Arms.

We knew that the River Severn is Britain's longest river.



And that the Thames is the deepest.

Not much gets past us on a good day. But which river has the greatest flow was beyond our little brains.

Anybody know?


« Last Edit: 01 October, 2010, 12:36:10 PM by P-Kasso »
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Wumpus

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Re: Which river in Britain has the largest flow?
« Reply #1 on: 01 October, 2010, 01:02:45 PM »
It's a bit of a meaningless question, if you ask me.

For example, I do know that the River Mersey has a tidal difference at its mouth of something like 28 feet, which is a pretty big height difference.
The second biggest in Britain (first is the Severn).

Would this tidal flow count towards your expected answer?

At what point do you measure flow?  Not many rivers would have much flow near their source.

Offline AtMyWitzEnd

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Re: Which river in Britain has the largest flow?
« Reply #2 on: 01 October, 2010, 06:40:23 PM »
River Flow Data is published by the Centre for Ecology and Hydrology for each year back to the 1930s. Just click on the link to say you accept the terms and conditions and it is all available. If you look at the data for each river you expect to be a contender for the latest year available (2008), you can compare the flows. The mean flow is shown at the bottom (also the best yearly mean and the year it was achieved).

This is very complicated data though because the runoff can vary enormously. The site explains this in detail, Each set of data lists the possible factors that might affect the runoff for that river system.

http://www.ceh.ac.uk/data/nrfa/river_flow_data.html

This article has some interesting data about the flow of the River Thames (about half way through) and explains the difference between the tidal basin (from the Port of Lnndon) and the river, although the river is only fresh water down to Toddington.
http://www.the-river-thames.co.uk/thames.htm
« Last Edit: 01 October, 2010, 06:54:08 PM by AtMyWitzEnd »

Offline antonymous

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Re: Which river in Britain has the largest flow?
« Reply #3 on: 02 October, 2010, 10:35:10 AM »
From the data supplied by the CEH site it looks like the TRENT has the highest flow rate.
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Offline P-Kasso2

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Re: Which river in Britain has the largest flow?
« Reply #4 on: 02 October, 2010, 11:26:20 PM »
.
I've enjoyed reading the thoughts and answers so far...and have an apology to make to you for being wooly.

After a a brief return to the Brewer's Arms this Saturday lunchtime, one long-term inmate said he was pretty sure
(from research he'd done since) that the River Tay in Scotland was the river that discharged the most volume of water.

That is, the Tay has the greatest flow by volume (ie in cubic metres of water discharged into the sea).

My wording in the original post was foggy. So Wumpus is definitely right, it was a bit of a meaningless question...
at least as worded by me then. Apologies from me.

So, suitably corrected, in terms of the most cubic metres of waters discharged by any river in Britain
(not just England), which river discharges the greatest volume of water into the sea?

Is the old  geezer in the Brewer's right? Is it the Tay or some other river? Your answers are going to cost me a pint.
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Offline AtMyWitzEnd

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Re: Which river in Britain has the largest flow?
« Reply #5 on: 03 October, 2010, 10:30:12 AM »
Looking at the tables from CEH, since you obviously think it below you lol, the River Tay is indeed the correct answer. In fact the summary for the gauging station at Ballathie (for 2008 figures) says; "90m wide. The most d/s station on the Tay, records highest mean flow in UK". The mean flow in 2008 was 208.5 CuM/Sec.

The Tay is a convincing winner, compared with the Trent at 98 CuM/Sec (as researched by antonymous as the highest in England), the Severn at 69 CuM/Sec and the Thames at 83 CuM/Sec.


Paul Chappell

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Re: Which river in Britain has the largest flow?
« Reply #6 on: 07 January, 2014, 01:29:10 PM »
The largest in the Uk is the Tay, the largest in England is the Yorkshire Ouse

Nubcake121

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Re: Which river in Britain has the largest flow?
« Reply #7 on: 14 December, 2015, 02:38:40 PM »
In terms of discharge,  i.e. the volumetric flow (m^3/s), the Tay does appear to be the winner but if you are speaking the flow, i.e. the speed of the river, then the Spey is the faster. Although as wiki states the Spey is the fastest in Scotland and potentially the UK depending on what you count as a river.

Take form that what you will but as I'm from the north-east of Scotland the Spey is the fastest river in the UK to me.

Hope you can get that pint back with interest added!

Offline seacommander

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Re: Which river in Britain has the largest flow?
« Reply #8 on: 16 December, 2015, 12:08:48 PM »
.
Dispute raged last night at the Brewer's Arms.

We knew that the River Severn is Britain's longest river.



And that the Thames is the deepest.

Not much gets past us on a good day. But which river has the greatest flow was beyond our little brains.

Anybody know?


Interesting about the Thames PK. How deep is the Thames and where is the deepest stretch?


Offline P-Kasso2

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Re: Which river in Britain has the largest flow?
« Reply #9 on: 17 December, 2015, 11:53:24 AM »
Try as I might, Seacommander, I can't find anyone (from Wiki to The Encyclopaedia Britannica and back) who is willing to say how deep the Thames is.

Is it some kind of state secret? Nowhere could I find a definitive answer to how deep is the Thames.

However I can say that, however deep it is, the Thames becomes 7 metres deeper at high tide (because the Port of London Authority says so).

Sadly, after sleuthing merrily around the Net, it is clear that it is only those wonderful folks at Ask and Yahoo who are even prepared to hazard a guess at how deep the Thames is. They say it is 37 feet deep but whether that is at high tide or at low tide or whether you can take what they say with any credence I cannot say.

Is there anybody else out there who can answer Seacommander's question more fully? I know I can't.
« Last Edit: 17 December, 2015, 11:55:55 AM by P-Kasso2 »
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Offline antonymous

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Re: Which river in Britain has the largest flow?
« Reply #10 on: 17 December, 2015, 01:32:04 PM »
" How deep is the River Thames?
In the estuary the charted depth (which can for most general purposes be considered as the depth at low water) is about 20 metres at its deepest . To get the depth of water at Mean High Water Springs (MHWS) you can add about 5 metres to that depth. At Mean High Water Neaps (MHWN) you only need to add about 4 metres.
Opposite Southend the charted depth is about 11 metres. Add about 5.7 metres to get the depth of water at MHWS and 4.8 metres at MHWN.
At Tilbury the charted depth is about 9.8 metres. Add about 6.4 metres to get the depth of water at MHWS and 5.4 metres at MHWN.
At Woolwich the charted depth is about 6.5 metres. Add about 7.0 metres to get the depth of water at MHWS and 5.9 metres at MHWN.
At London Bridge the charted depth is about 1.8 metres. Add about 7.1 metres to get the depth of water at MHWS and 5.9 metres at MHWN.
At Westminster Bridge the charted depth is about 1.9 metres. Add about 6.8 metres to get the depth of water at MHWS and 5.6 metres at MHWN.
At Hammersmith Bridge the charted depth is about 1.4 metres. Add about 5.7 metres to get the depth of water at MHWS and 4.6 metres at MHWN.
At Richmond the charted depth is about 1.0 metre. Add about 4.9 metres to get the depth of water at MHWS and 3.7metres at MHWN.
On the navigable section of the Non-tidal Thames (Teddington to Lechlade) the depths range from about 3.0 metres to 0.9 metres. The depth of water is controlled by the Environment Agency (EA) by adjusting the height of the weirs. The EA also endeavour to maintain a minimum dredged depth on the non-tidal River. It is not a constant depth: it varies depending on the section of river: "
[oops!] a vastly inferior question and answer site
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Offline P-Kasso2

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Re: Which river in Britain has the largest flow?
« Reply #11 on: 18 December, 2015, 03:06:26 PM »
Very interesting stuff, Ant. It'd be good to know where the [oops!] a vastly inferior question and answer site you quote got all their original info from. I couldn't find anything anywhere near like it.

My [oops!] a vastly inferior question and answer site firmly stated that the Thames was exactly 37 feet at its deepest.

There's a big difference between 37 feet and 24 metres at high tide. Thinking the Thames was over 78 feet deep or just 37 feet deep could be crucial.

Having 40 odd feet less draft under your keel than you thought could mean the difference between a nice pleasure jaunt and spending an embarrassing cold and wet night on a mud bank.
« Last Edit: 18 December, 2015, 03:09:50 PM by P-Kasso2 »
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Offline antonymous

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Re: Which river in Britain has the largest flow?
« Reply #12 on: 18 December, 2015, 06:38:15 PM »
The question  "how deep" is ambiguous and should [ I think]   have been "what is the greatest depth of water found along the entire length of the River Thames"

I suspect all the data quoted comes from the The United Kingdom Hydrographic Office (or UKHO) chart makers.

"Admiralty charts are nautical charts issued by the United Kingdom Hydrographic Office[1] and subject to Crown Copyright. Over 3,000 charts are available and cover virtually the entire world in various levels of detail depending on the density of traffic and hazards. Large-scale charts often cover approaches and entrances to harbours, medium-scale charts cover heavily used coastal areas, and small-scale charts are for navigation in more open areas. There is also a Small Crafts Series available at even smaller scales.

Charts include: depths (chart datum), coastline, bouyage, land and underwater contour lines, seabed composition (for anchoring), hazards, tidal information ("tidal diamonds"), prominent land features (e.g. church towers), traffic separation schemes, RF direction finding information, lights, and in short anything which could assist navigation." wiki
« Last Edit: 18 December, 2015, 09:31:30 PM by antonymous »
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Offline seacommander

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Re: Which river in Britain has the largest flow?
« Reply #13 on: 19 December, 2015, 02:27:40 PM »
Thanks chaps for the information. My question was prompted from my surprise how shallow the River Great Ouse is for most of its length. For the non tidal sections, as with the Thames, charted depths rarely exceed 1.5 metres. Similarly, the tidal section of the Great Ouse has a considerably greater depth of course varying with the tide. I had oftened wondered that should my narrowboat capsize would it disappear from view, however, it seems that at least half of it would remain above the surface; but I don't wish to prove this in practice!
« Last Edit: 19 December, 2015, 08:51:35 PM by seacommander »

Offline P-Kasso2

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Re: Which river in Britain has the largest flow?
« Reply #14 on: 20 December, 2015, 12:04:11 PM »
Thanks chaps for the information. My question was prompted from my surprise how shallow the River Great Ouse is for most of its length. For the non tidal sections, as with the Thames, charted depths rarely exceed 1.5 metres. Similarly, the tidal section of the Great Ouse has a considerably greater depth of course varying with the tide. I had oftened wondered that should my narrowboat capsize would it disappear from view, however, it seems that at least half of it would remain above the surface; but I don't wish to prove this in practice!

Ahoy SC! Have you got any photos of your narrowboat you'd care to share? It'd be great to see them.
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