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Phosphorus dynamics observed through increasing scales in a nested headwater-to-river channel study
P M Haygarth1, F L Wood, A L Heathwaite
1Soil Science and Environmental Quality Team, Institute of Grassland and Environmental Research (IGER), North Wyke Research Station, Okehampton, Devon EX20 2SB, UK. phil.haygarth@bbsrc.ac.uk
The Science of the Total Environment
|May 24, 2005
Summary
Phosphorus (P) transport dynamics differ across plot to river basin scales. Agricultural runoff significantly impacts P export, especially during storm events, highlighting scale-dependent processes.
Area of Science:
- Environmental Science
- Hydrology
- Biogeochemistry
Background:
- Understanding phosphorus (P) transport across different spatial scales is crucial for managing water quality.
- Previous studies have often focused on single scales, limiting insights into cross-scale P dynamics.
- The hypothesis tested is that P transport patterns are scale-invariant from plot to river basin levels.
Purpose of the Study:
- To test the hypothesis of similar P transport dynamics (inputs and dilution) at plot and river basin scales.
- To infer the connectivity and mass flux of P transport between observation scales.
- To investigate the influence of rainfall and runoff conditions on P transport across scales.
Main Methods:
- An intensive field study was conducted in the River Taw basin, UK.
- Data were collected from 30-m², 1-ha plots, and nested river channels (20 ha to 834 km²).
- Three hydrological campaigns were performed: base flow, residual flow (10-mm rainfall), and storm flow (42-mm rainfall).
Main Results:
- Total P mass flux varied significantly, from 49 kg (base flow) to 4 tonnes (storm period) at the largest scale.
- During storm flow, total P concentrations increased across all scales, overriding point source inputs.
- P attenuation and dilution were greater at larger scales, while hydrological connectivity was highest at smaller scales during high flows.
Conclusions:
- Phosphorus transfer processes are scale-dependent, contradicting the initial hypothesis of similarity.
- Diffuse agricultural sources are significant contributors to P export, driven by hydrological dynamics and particulate P.
- Further research is needed to address uncertainties in spatial heterogeneity and scale-dependent P transport.