An investigation into the impact of nine catchment characteristics on the accuracy of two phosphorus load apportionment models

Jamie Lee Stevenson, Sean O'Riordain, Edwin Harris, Lucy Crockford* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Phosphorus (P) load apportionment models (LAMs), requiring only spatially and temporally paired P and flow (Q) measurements, provide outputs of variable accuracy using long-term monthly datasets. Using a novel approach to investigate the impact of catchment characteristics on accuracy variation, 91 watercourses’ Q-P datasets were applied to two LAMs, BM and GM, and bootstrapped to ascertain standard errors (SEs). Random forest and regression analysis on data pertaining to catchments’ land use, steepness, size, base flow and sinuosity were used to identify the individual relative importance of a variable on SE. For BM, increasing urban cover was influential on raising SEs, accounting for c.19% of observed variation, whilst analysis for GM found no individually important catchment characteristic. Assessment of model fit evidenced BM consistently outperformed GM, modelling P values to ±10% of actual P values in 85.7% of datasets, as opposed to 17.6% by GM. Further catchment characteristics are needed to account for SE variation within both models, whilst interaction between variables may also be present. Future research should focus on quantifying these possible interactions and should expand catchment characteristics included within the random forest. Both LAMs must also be tested on a wide range of high temporal resolution datasets to ascertain if they can adequately model storm events in catchments with diverse characteristics.
Original languageEnglish
Article number142
Number of pages14
JournalEnvironmental Monitoring and Assessment
Issue number3
Early online date24 Feb 2021
Publication statusPublished - 1 Mar 2021

Bibliographical note

Funding: No funding was provided for this study aside from supervisory support through Harper Adams University.

Data Availability Statement

Data were sourced from the National River Flow Archive and the EA historical river water quality. These were obtained under licence and are unavailable for distribution without the express permission of NRFA or the EA.


  • Phosphorus
  • Load apportionment model
  • Modelling
  • Certainty
  • Catchment


Dive into the research topics of 'An investigation into the impact of nine catchment characteristics on the accuracy of two phosphorus load apportionment models'. Together they form a unique fingerprint.

Cite this