Water Quality Implications of an Observed Trend of Rainfall and Runoff

The catchment of the upper Clyde estuary has experienced a significant and steady increase of rainfall over the past twenty years. The corresponding increase of runoff has had a positive impact on the water quality both of the individual rivers and of the estuary. Examples are provided to show that approximately one third of some observed improvements are attributable to the additional dilution. It is emphasized that comparisons of water quality data, either by region or by period, should allow for climate variability.