Leading article: Water of life

Where there is life there's hope. And that certainly applies to our rivers.

Yesterday we reported on the return of salmon to the once dreadfully polluted watercourses of South Wales. And the explanation for that turnaround is the fact that the water quality there has improved significantly in the past two decades.

But life in the water is not a simple matter. Another river which has improved its quality in recent years has been the Thames in London. And yet, as we report today, the eel population has almost entirely collapsed in the capital's main waterway. Researchers from the Zoological Society of London suggest a number of potential causes, from changes in oceanic currents due to climate change, to disease, to man-made dams.

Whatever the explanation, the discrepancy between the fortunes of British salmon and eels serves as a reminder that, if we want life to flourish fully once more in our national rivers, clean water is only part of the solution.