cleanliness of southern rivers

[david t]

Hello,

im beggining to question the overall cleanliness of the rivers in the southeast. Ive spent abit of time fishing in wales recently, and coming back to the south eastern rivers, i get the feeling they arent that pristine, the same goes for the canals as well. What i mean is that, im sure back say 10 years ago i dont remember the rivers being murky and green in summer so much, but over the last two summers, i cant help but notice they have a sluggish feel to them. The water clarity seems worse, and alot of areas seem to have quite alot of filamentous algae in the riffles. I get the impression there is more nutrient going into our rivers now than before. I mean, look at how many sewage treatment works (STWs) there are along the rivers. Take the river thame for instance, its about 20 miles long, at a guess, maybe more, and it has 2 or 3 large STWs and at least 10 minor STWs along its length, this must be pilling alot of excess nutrient into the rivers. Im not talking about physical muck and crap in the rivers, its this excess of phosphates, nitrates and other such nutrients.

 

And with more houses being built in the south east this can only get worse. I think the water companies only do as much as they have to maintain their image, as an environmentally friendly company. Im sure they could do more to make sure what they put back into water is as close to natural river water as possible, but they never will.

 

does anyone else think the rivers in the south maybe arent that clean anymore?

dave

[Steve Walker]

The lowland rivers in the South East are likely naturally to have a richer trophic status than short, predominantly upland Welsh rivers, and more suspended solids too. Having said that, I'm sure that there is a large nutrient load going into rivers in the South East from both treated sewage and agricultural runoff, and increasing population density can only exacerbate that problem. It's generally the case that river water quality has been improving for the last 2-3 decades, but I think the focus has been on reducing BOD and ammonia levels rather than on eutrophication. The EU Urban Wastewater Treatment Directive does concern itself with eutrophication, however, and looks to be forcing the increased use of phosphate recovery for sewage effluent.

 

By the way, I don't know what it's like now, but the small river flowing into the sea at Clarach Bay used to be absolutely minging with sewage; I certainly wouldn't have entered the sea there.

Edited September 5, 2007 by Steve Walker

[starlight]

when i first fished the kennet 20 years ago it had a real ping and clarity about it, you really felt that you could cup your hands and drink it. over the next 15 years i watched it deteriorate, as dave said it become sluggish and the prolific streamer weed and the water clarity disappeared but it never actually seemed to affect the fishing which other than the grayling disappearing seemed to improve! with both chub and barbel getting much bigger!. here i fish the dordogne and it has the same ping and clarity as the kennet used to have but fishing wise the kennet knocks the pants off it!.

[Steve Walker]

Starlight, this may interest you:

 

http://environment.info/commondata/acrobat...lity_835804.pdf

 

look at the case study for the Kennet.

Edited September 5, 2007 by Steve Walker

[Unimexsol]

Conversely I think that the canals and river in and around London have improved greatly in the last 10 years.

[david t]

steve, I know, as you say that the lowland rivers around the south are naturally more rich than those in the uplands of wales, but i still think they have reduced in flow, and have a higher nutrient load. It was last summer, that i first saw the greyish filamentous bacterial biofilm deposit (that usually occurs in the area immediately surrounding a sewage outfall) on the stones of a shallow riffle on a local river, which is indicative of nutrient overload. I did inform the EA, but i never saw them down there, it seems its just a permanent occurence now. And that river at clarach bay is fairly clean now, but I wouldnt swim in it, but thats because its bloody cold!

 

Ive kind of lost touch abit with the Water Framework Directive, but I do hope that the big shake up, concerning various pollutants will maybe clear this up in the future.

 

Unimexsol, I know what you are saying, I suppose london waterways are visibly cleaner, in that there is less rubbish, raw sewage, and obvious chemical pollution, which is all good, but im more concerned with the nutrient loading.

 

one last thought, isnt the set aside scheme for farmers being abolished now? so an extra 8% of land will be farmed now, adding more nutrient to the area. I might have heard it wrong, but i think im correct in that its being abolished.

cheers

dave

[starlight]

that was interesting steve, certainly explains whats going on.

[poledark]

Thanks for the link Steve

 

Den

[Dick Dastardly]

Interesting stuff.

[Steve Walker]

steve, I know, as you say that the lowland rivers around the south are naturally more rich than those in the uplands of wales, but i still think they have reduced in flow, and have a higher nutrient load.

 

I'm pretty sure you are right, but I did think that maybe spending some time in rural Wales had spoilt you a bit It's very likely that the rivers you have in mind have suffered an increased nutrient load from agriculture and processed sewage at the same time as a decrease in flow due to abstraction. I think we just have to hope for more nutrient stripping of effluent and less over-use of fertilisers.