Detection of transient pollution events in an Irish river catchment in the context of increasing frequency and intensity of rainfall events due to climate change

Keywords

Freshwater pollution, climate change, water quality monitoring, emerging contaminants, diffuse agricultural pollution, catchment monitoring.

Abstract

Despite the implementation of river basin management plans across EU, river water quality is in decline with agriculture, forestry and hydromorphological pressures now the dominant pressure for river waters in Ireland.  The number of high quality river sites reflecting natural, undisturbed conditions declined from 31.6% of river sites monitored in 1990 to just 1.1% of monitored sites in 2021¹. 

Climate change increases in heavy rainfall events in conjunction with flooding will lead to increased suspended solid and nutrient loadings in rivers² with a substantial upsurge in the intensity of winter rainfall together with increasing frequency in heavy rainfall events³ in Ireland⁴ leading to increased pollution of freshwater systems and a surge in transient pollution events.

‘Reliable high quality information on the environmental quality of surface waters’ is critical for  agencies to make evidence based decisions on appropriate management measures to restore water quality at European scale⁵.  However current water quality monitoring programmes in Ireland rely heavily on grab water samples which is inadequate at detecting transient pollution⁶. 

Are transient pollution events contributing to increased solids, nutrients loads and emerging contaminants affecting aquatic species in these declining Q5 sites?  This research aims to investigate by applying field assessments, sensor technology and automatic sampling to two river stations in the North West of Ireland; on the River Unshin a high ecological status water body and on the River Owenmore, a moderate ecological status water body.  As the pathway from land to waters for multiple diffuse agricultural pollutants, including phosphorus, sediment and pesticide are similar⁷ and turbidity can be used as an indicator for suspended sediment⁸, a baseline turbidity survey is being carried out to identify a ‘trigger level’ above which the collection of water samples is initiated. 

Other research has shown no simple relationship between discharge, turbidity and precipitation⁹ but initial baseline data obtained shows some correlation with turbidity and increased flows.

References

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