Far-future hydrology will differentially change the phosphorus transfer continuum

Area of Science:

• Environmental Science
• Hydrology
• Water Quality Management

Background:

• Climate change intensifies land-to-water phosphorus (P) transfers, degrading freshwater quality in Northwestern Europe.
• Understanding P loss dynamics under changing hydrological regimes is crucial for effective mitigation planning.

Purpose of the Study:

• To assess the impact of climate-induced hydrological changes on the P transfer continuum in six contrasting Irish river catchments.
• To estimate changes in total P (TP) and total reactive P (TRP) transfer processes under future climate scenarios (RCP4.5 and RCP8.5).

Main Methods:

• Utilized far-future climate scenarios (RCP4.5, RCP8.5) of modelled river discharge.
• Linked observed hydrological regimes (baseflow, flashiness) to P transfer processes (mobilisation, delivery indices).
• Compared projected P transfer processes for 2080 (2070-2099) against 2020 (2010-2039) baseline.

Main Results:

• P mobilisation is projected to remain relatively stable across catchments under both RCP scenarios.
• P delivery is highest in flashy catchments, with significant increases projected in groundwater-fed catchments under RCP8.5 (+22% TRP, +24% TP).
• Inter-annual variability of P delivery is expected to rise in groundwater-fed systems.

Conclusions:

• Hydrological connections to P mobilisation areas are increasing, making them critical targets for mitigation.
• Focusing on hydrologically connected areas with favourable P mobilisation conditions (soil/bedrock chemistry, biology, hydrology) is recommended.
• Effective water quality management requires targeted strategies addressing critical P mobilisation zones, not solely P source magnitudes.