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dredger

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Why do the broads and the rivers become clear at this time of the year? I thought it was water temperature but it's not got cold but it has got clear!

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6 minutes ago, dredger said:

Why do the broads and the rivers become clear at this time of the year? I thought it was water temperature but it's not got cold but it has got clear!

Hi Dredger,

Welcome to the NBN Forum :wave As for your question, I am sure someone will be along soon with a possible diffinitive answer.

cheersIain

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Two weeks ago the bure up towards Coltishall was very clear (could see the fish etc)., Wroxham broad is extreemly clear this week and as I walked throgh Norwich Yesterday the Wensum was noticably clearer. Was on Salhouse last week but can't remember the water (could it be the beer!). It always seems to happen at this time of year but why? Not so much to stir the mud or does the algae drop for the winter?  I'll probably go down to Malthouse tomorrow so I'll see what it's like there.

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I have seen it very clear up at Coltishall, also at Norwich Yacht Station, the clearest of all at West Sommerton. However, all at different times of the season. Coltishall in May, Wensum in Mid October, West Sommerton in early July.

cheersIain

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These are towards the head of navigation, Wroxham broad is very clear again today,  I'll check out the river tomorrow, it seems to suddenly happen each year around this time , There must be a reason for it.

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The water has always been clear at Norwich and Coltishall whenever I have been. Same after Stalham , I,always thought it was due to less salt in the water. 

Wroxham broad is probably my least faviroute broad. Alway blowing a gale anytime I've been on it. Not a very welcoming broad in more ways than one.

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Hi Dredger, I guess it's because there's fewer boats out and thus less stirring of the mud. I've seen pike chasing prey at coltishall. Nice to see.. Enjoy, cheers 

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I believe West Somerton is always so clear due to salt water springs leaching through from the sea. Certainly the water weed there more resembles proper seaweed.

A very old local, long gone now told me as a teenager that the stories of a clear patches in Hickling and Horsey ended with the hard defences installed after 1953 because they cut off the patches of salt water spring.

Could just be rubbish though as there were huge Pike about and they don't like salt.

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i've always lived here but have only recently come back to rivers lots is lost to me but I have noticed every year the rivers and broads dropping bright and clear at this time of the year, it's not salt where i am (up the bure) there's a surprising variety of water plants, something causes it but what?. Also don't pike survive in the baltic?

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The Waveney is clear from North Cove to Geldeston, though Geldeston is usually clear all year, and has been pretty much since mid August. You can certainly see the bottom in the yacht station, it needs dredging by the way!

And welcome from me Mr Dredger sir!

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I strarted having broads holidays in the 1960s, the water is far clearer almost everywhere than it used to be. Less toilet paper too. :)

I'm sure the drop in boating traffic has much to do with the improving clarity.

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I remember the year (but not thr date) before they stopped sewage discharge it was very clear and the year after extreemly murky, can only suppose the change upset the system ecology.  Suurely also some of you can remember the other items tat decorated the reed beds! The sudden seasonal clarity is a mystery.

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Hi Dredger and welcome, there are a number of reasons, all the higher reaches like Coltishall are always clear except periods of heavy rainfall, lower down its a combination of low rainfall and this time of year colder evenings and nights lowering the water temperature, less boat traffic and possibly Daphnia blooms clearing the algae on Wroxham Broad not the case at Malthouse which is still pea green, it is also noticeable the general increase in weed growth especially the middle Bure which indicates clearer and cleaner water in general.

Fred

 

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I think there are lots of factors here, and welcome to the forum Dredger. Do you do any dredging by the way? We have need of it!

I know little about Hickling but the Yare and the Bure, although tidal, are flowing out to sea the whole time. Hence the flow over the weir at New Mills in Norwich, and the reason why there were locks at Coltishall. So the upper reaches will often be clear water coming from further inland unless, as Fred says, there has been heavy rainfall, when they become alluvial, and are carrying silt from the surrounding fields.

Other than that, it is a matter of the actual water quality, in different circumstances. I am old enough to remember when the Yare and the lower Bure were gin clear but I fear I have never seen Wroxham Broad look anything other than Brown Windsor soup. Not sure why that is, as it is a large expanse of still water which should not be stirred up too much by the movement of boats. At least it is a dull colour, as over-enriched water will be a bright green.

Or of course it could be because the rivers are now all that is left of the Great Estuary. (Timbo owes me that one, for referring to my scale model railway as toy trains!)

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51 minutes ago, Vaughan said:

Or of course it could be because the rivers are now all that is left of the Great Estuary. (Timbo owes me that one, for referring to my scale model railway as toy trains!)

Love it :)

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54 minutes ago, Vaughan said:

of course it could be because the rivers are now all that is left of the Great Estuary. (Timbo owes me that one, for referring to my scale model railway as toy trains!)

Hmm blasphemy that is, Vaughan, toy trains they are most definately, not !!! Model Railway if you please:party: That archipeligo or whatever you wish to call him type chap had better watch his Ps n Qs. Its time RT was completed! :wave

cheersIain

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In my opinion the rain fall thing is true, the downward flow at the head of navigation is true but there's something happening  every autumn in other areas! The edges of wroxham broad were clear enough to be able to see the bottom yesterday and it's been like that at this time of the year in previous seasons. I'll check further afield this afternoon.

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When I was coming to the Broads in the 60s the only place I saw white water lilies was Martham Broad, in the last 20 years yellow ones took up residence in Horning. This year for the first time I have seen white in Horning. I am assuming due to water quality although someone else may correct me?

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Oi you three...just for that I'm going to give you a headache... and answer the question!:naughty:

Hi Dredger welcome to the forum. What you are seeing is a seasonal action seen in most temperate lakes or in our case 'Broads' due primarily to stratification of the water and the natural processes of aquatic plants. The water can be divided into three layers. The epilimnion which is the top layer or surface layer of the water, the hypolimnion which is the bottom layer of water and the thermocline which is the area where the top and bottom layers meet and there is a rapid fall in temperature between the top and bottom layers.

In the summer and winter months there is a distinct stratification of the water. In other words the temperature difference between the top and the bottom of the water is large. The colder the water, the more dense it is. So the thermocline acts as a barrier, the warm water of the surface sliding over the cold water at the bottom. This stops the water mixing.

The  hypolimnion or cold layer of the Broad has a greenish colour thanks to the plants and algae which reside there, not to mention the dark peat. However throughout the summer and winter the hypolimnion becomes starved of oxygen, the thermocline prevents the oxygen rich epilimnion from mixing with it. Respiration of aquatic plants and animals can make matters worse. The bacteria that break down the dead matter starts to do so anaerobically. However plant matter unprocessed by the oxygen starved bacteria builds up and the water of the hypolimnion becomes nutrient rich and stagnant. A dark green sulphurous soup I'm sure we've all caught a whiff of when pulling up the mudweight. So throughout the summer and winter when you look into the water you are peering through the clear warmer water of the epilimnion down to the stagnant gunk in the hypolimnion.

Now to keep from becoming stagnant mires of filth, water requires energy to mix the top and bottom layers of water to bring oxygen down to it on a regular basis. Energy in the form of wind and of course BOATS!

Twice a year, dependant upon the stupid weather we get these days, the temperature of the epilimnion and hypolimnion match and the waters mix. Floods of rich nutrients and algae surge from the bottom and oxygen is flushed from the top.

It is during these mixing periods that the water clears and this is what you are seeing now.

Now I'm sure everyone is putting two and two together much faster than I did and realise that a rant is on the way.

It's during the spring when the waters and nutrients mix, at these times we get algal blooms from the stagnant, to use the correct scientific term, weed choked waters of Hickling. Poor land management in allowing water to become unaerated, weed choked, quagmires in the name of misguided ecology. This is the reason some fat cat in Wroxham is dipping into public funds to finance the cleanup of the cesspool they've turned Hoveton Great Broad into. And incidentally I think it's time the Broads Authority started sticking to its actual job in 'promoting' the navigation, as in the correct definition of 'promoting' making more water navigable...not trying to advertise courses in paddle boarding, basket weaving and bird watching. I wouldn't trust Dr Doom to mow my lawn let alone manage the Broads.

Please excuse the rant towards the end Dredger and I hope I didn't give you a headache?

I blame it on too many nutrients from breakfast...I'm collecting cereal packet tops for a PhD in ecology...hang on...to much All Bran...explains what comes out of the upper echelons of Yare House these days! :naughty: 

 

 

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51 minutes ago, Timbo said:

What you are seeing is a seasonal action seen in most temperate lakes or in our case 'Broads' due primarily to stratification 

Oh I do like that word Tim! :clap

cheersIain

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