Green River

[Mac of Cygnet]

The river at Ely is completely covered at the moment with a thick layer of duckweed. Not just ordinary duckweed, but a much less common species, greater duckweed (Lemna polyrhiza to be technical). It closes like a curtain to an apparently solid surface as the boat ploughs through. I've never seen this before here. Does it happen every year? I haven't had a look at my raw water strainer yet......

 

[Athy]

I don't think it happens every year, but I remember the North Oxford being similarly afflicted some years ago.

[Phil Ambrose]

I've not seen it as bad as this but I've only been in these parts for 4 years, only ever seen it in patches in the past.

Phil

[Naughty Cal]

The Witham gets patches of that but often accompanied by stringy weed underneath.

 

I would check your raw water filter!

[magnetman]

Limehouse cut going into the marina is a lawn too.

I'm going through it tomorrow, plays havoc with my engine cooling mud box

I think its ordinary duck weed here don't know. CRT have a boat which takes some of it out but I reckon it'd take a week to sort it out.

[magnetman]

View from the dinghy. That was early July and its still like that if not worse.

 

 

 

[Tim Lewis]

Pretty well the whole length of the canal from Thorne to Keadby looked like this the day before yesterday!

 

Tim

[oasistoo]

The river at Ely is completely covered at the moment with a thick layer of duckweed. Not just ordinary duckweed, but a much less common species, greater duckweed (Lemna polyrhiza to be technical). It closes like a curtain to an apparently solid surface as the boat ploughs through. I've never seen this before here. Does it happen every year? I haven't had a look at my raw water strainer yet......

 

Selby canal in same state so thick in basin did not need fenders down!

[gazza]

Christ that's getting bad.

 

Clear as a bell two weeks ago!

 

Constant rodding of our filter on trip from popes corner to Ely last Sunday.

[IanM]

We used to get it a lot on the Stroudwater. There was a time when we had the purple variety.

 

Blunder Lock - Stroudwater Canal by imulford, on Flickr

 

Can't believe that was 20 years ago now!

[pete.i]

Selby canal in same state so thick in basin did not need fenders down!

Yep they have 2 tiny boats trying to clear the Selby canal. Last day today and they have only got as far as the boatyard. It's not the blokes fault doing the job they don't stand a snowball in hells chance of clearing the, relatively, short Selby canal.

[Phil Ambrose]

I think this weed is what's called Fairy Moss (under some conditions turns purple)

Our marina basin is swamped with weed at the moment, almost impossible to row through! Clogging a lot of props too.

Phil

[pete.i]

I haven't taken my boat out in a couple of weeks The last time I took a trip down the Selby the weed stopped my engine once completely and twice nearly stopped it. 3 trips down the weed hatch in 5 miles was too much for me. I know some do more trips down the hatch than that in as few miles but I couldn't be bothered so my boat has stayed in the boatyard since. I have to say it wasn't that surface stuff that stopped my engine it was bind weed below the surface. some of it is yards long and it's a sod to get off. That duck/fairy/moss/surface whatever it's called weed doesn't seem to bother me. My raw water intake is well below the surface and I have an inboard filter.

[Peter X]

Some years back when I was going through a tropical fishkeeping phase I used to be plagued by duckweed, rapidly multiplying to cover the surface of a tank and killing off most plants below them by blocking out light; so you might expect less of the bigger and more troublesome weeds where there's a lot of duckweed?

 

This is a comprehensive article on duckweeds:

http://www.ceh.ac.uk/sci_programmes/documents/duckweeds.pdf

 

Basically they multiply on still or slow waters with enough organic nutrients, so for our purposes the Fenland rivers would be a likely place to see duckweed, or any canal with enough fertiliser running in off farmland.

 

Towards the end it basically says boaters are all to blame for not cruising about enough on the affected waters!:

"The minimum amount of boat traffic required to eliminate Lemna is reckoned to be about 1500 boat movements per annum"

It doesn't elaborate as to what kind of boat; do widebeams count as two I wonder? Anyway, well done the OP or making a start on the problem.

[J R ALSOP]

Well that will give the continuous cruisers a good excuse for not moving.

[Daiboy]

We used to get it a lot on the Stroudwater. There was a time when we had the purple variety.

 

Blunder Lock - Stroudwater Canal by imulford, on Flickr

 

Can't believe that was 20 years ago now!

 

Must have been as there's no handrail on the gate crossing planks !

[saltysplash]

for the first time in the six years weve been on the slough arm we are totally weed free which is very unusual but thanks to the dredging that had taken place between highline and the basin.

 

Sadly they ran out of money so didnt do the couple of miles towards cowley

[MHS]

A couple of years ago we visited the museum at Ellesmere Port.

 

They were clearing weed on a daily basis. At least 2 children had run into the canal assuming it was grass.

[PiRSqwared]

Limehouse cut going into the marina is a lawn too.

I'm going through it tomorrow, plays havoc with my engine cooling mud box

I think its ordinary duck weed here don't know. CRT have a boat which takes some of it out but I reckon it'd take a week to sort it out.

Wait til you get up to the green bridge...duck weed plus the stuff that grows on the river bed...

[ditchcrawler]

The Old West river was very bad between The Fish and Duck and Hermatage Lock about 3 years ago, didn't cause us a problem but cruisers with raw water cooling where really struggling at times.

[gazza]

The Old West river was very bad between The Fish and Duck and Hermatage Lock about 3 years ago, didn't cause us a problem but cruisers with raw water cooling where really struggling at times.

Don't I know it!

 

We have decamped from the Nene to the Ouse for the summer.

Wise move e?!

[blackrose]

A couple of years ago we visited the museum at Ellesmere Port.

 

They were clearing weed on a daily basis. At least 2 children had run into the canal assuming it was grass.

 

It can be quite dangerous. Several years ago I saw a big shaggy dog run straight onto a load of weed and floating grass cuttings that had accumulated above the sluice at the end of the Brentford basin. It was a couple of days after heavy rain and the dog never came back up. It just got sucked straight into the sluice and must have got stuck there because we couldn't see it come out the other side.The owner was distraught. Everyone around hearing his cries thought he'd lost a child. It could easily have been. BW quickly put up short posts and chains around the end of the basin after that.

Edited July 26, 2014 by blackrose

[Phil Ambrose]

I can relate to that, we used to moor on a small island when we were on the Broads and it had a small pond which was covered in duckweed, one of our dogs just trotted onto/into it unaware there was water beneath the green stuff.

Phil

[Mac of Cygnet]

 

The Old West river was very bad between The Fish and Duck and Hermatage Lock about 3 years ago

 

As it is at the moment. The pic is approaching The Lazy Otter. It's the same stuff as at Ely. There were purple patches in it, and I noticed that as I went through, there was a purplis bow wave, so I howked a bit out, and each thallus (leaf) is purple underneath, so the purple bits are upside down, not a different kind. There wasn't much in my raw water strainer at Ely, but after this lot it was pretty full! (But still working).

Spent last night on Wicken Fen and passed Scholar Gypsy moored near Pope's Corner.

 

[KJT]

The first part of the Basingstoke Canal, so far, up to St Johns Locks is the same. A total carpet of green.