Clarity trends at National River Water Quality Network sites, 1989-2007
Notes:
(1) A ‘meaningful’ trend is both statistically significant and environmentally meaningful, while a ‘significant’ trend is statistically significant but not necessarily environmentally meaningful (eg, the scale of the change could be very minor).
(2) An increase in visual clarity is seen as an improvement in water quality, while a decrease is seen as a decline in water quality.
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