Length of river in Thames catchment in ‘Good’ biological condition now lower than in 1995

We’ve heard a lot about improvements in the R. Thames recently, and I’ve just seen re-Tweeted this Environment Agency press release from 25th October 2010 which starts:

“Water quality in the River Thames area has improved over the past year, according to Environment Agency figures.”

So I looked at what’s actually happened in the Thames region – both chemically and biologically – using the Environment Agency’s data, and here are the results.

Chemically there was indeed a slight increase in the length of river at Good status between 2008 and 2009, the year with the most recent data.

That’s Graph 1 below.

Graph 1: Percentage of river length in the Thames catchment that was in chemical 'Good' condition between 1990 and 2009 (Click to enlarge graph).

But biologically, the length of river in Good condition is actually lower now than in 1995 (Graph 2).

Graph 2. Percentage of river length in the Thames catchment which was in biological 'Good' condition between 1990 and 2009 (Click to enlarge graph).

So it’s a bit misleading to imply that things are generally getting better in the Thames area.

Biologically – at least as measured by invertebrate animals – the opposite seems to be true, at least for the last 15 years.

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