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The Water Framework Directive establishes that both water quality and water quantity are essential components of sustainable water management. Protecting chemical status without considering hydrological balance, or managing quantity without addressing pollution pressures, would undermine the Directive’s integrated approach.
Water quality is directly affected by:
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Diffuse nutrient pollution from agriculture
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Sediment transport linked to erosion
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Pesticide and contaminant runoff
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Hydromorphological alterations
At the same time, water quantity is influenced by:
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Runoff generation and peak flow dynamics
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Groundwater recharge rates
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Abstraction pressures
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Seasonal variability intensified by climate change
The WFD explicitly links ecological status to hydrological conditions. A river’s ecological functioning depends not only on chemical concentrations but also on flow regimes, connectivity, and morphological structure. Excessive runoff, rapid transfer of nutrients, or insufficient base flow can all compromise the achievement of good ecological status.
In agricultural catchments, climate variability further complicates this balance. Intense rainfall increases erosion and nutrient leaching, while prolonged droughts reduce dilution capacity and stress aquatic ecosystems. Maintaining both hydrological stability and pollutant control is therefore central to WFD implementation.
Within OPTAIN, this dual dimension is addressed through integrated modelling at both field and catchment scales. Process-based simulations allow assessment of:
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Water balance components (infiltration, runoff, evapotranspiration)
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Nutrient transport pathways
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Sediment mobilisation under varying rainfall intensities
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System behaviour under projected climate conditions
This approach strengthens understanding of how retention measures influence both quantity and quality simultaneously. Importantly, modelling does not replace regulatory monitoring under the WFD. It supports decision-making by analysing potential measure impacts before implementation.
Maintaining water quality and quantity is therefore not a parallel objective but a combined ecological requirement embedded in basin management planning.