Hydro-chemical responses at different scales in a rural catchment, UK, and implications for managing the unintended consequences of agriculture

A - Papers appearing in refereed journals

Granger, S. J., Upadhayay, H. and Collins, A. L. 2023. Hydro-chemical responses at different scales in a rural catchment, UK, and implications for managing the unintended consequences of agriculture. Environmental Research. 228, p. 115826. https://doi.org/10.1016/j.envres.2023.115826

AuthorsGranger, S. J., Upadhayay, H. and Collins, A. L.

Diffuse pollutant transfers from agricultural land often constitute the bulk of annual loads in catchments and storm events dominate these fluxes. There remains a lack of understanding of how pollutants move through catchments at different scales. This is critical if the mismatch between the scales used to implement on-farm management strategies, compared to those used for assessment of environmental quality, is to be addressed. The aim of this study was to understand how the mechanisms of pollutant export may change when assessed at different scales and the corresponding implications for on-farm management strategies.

A study was conducted within a 41 km2 catchment containing 3 nested sub-catchments, instrumented to monitor discharge and various water quality parameters. Storm data over a 24-month period were analysed and hysteresis (HI) and flushing (FI) indices calculated for two water quality variables that are typically of environmental significance; NO3–N and suspended sediment (SSC). For SSC, increasing spatial scale had little effect on the mechanistic interpretation of mobilisation and the associated on-farm management strategies. At the three smallest scales NO3–N was chemodynamic with the interpretation of dominant mechanisms changing seasonally. At these scales, the same on-farm management strategies would be recommended. However, at the largest scale, NO3–N appeared unaffected by season and chemostatic. This would lead to a potentially very different interpretation and subsequent on-farm measures.

The results presented here underscore the benefits of nested monitoring for extracting mechanistic understanding of agricultural impacts on water quality. The application of HI and FI indicates that monitoring at smaller scales is crucial. At large scales, the complexity of the catchment hydrochemical response means that mechanisms become obscured. Smaller catchments more likely represent critical areas within larger catchments where mechanistic understanding can be extracted from water quality monitoring and used to underpin the selection of on-farm mitigation measures.

KeywordsChemo-dynamic; Chemostatic; Water quality; Nutrients; Sediments
Year of Publication2023
JournalEnvironmental Research
Journal citation228, p. 115826
Digital Object Identifier (DOI)https://doi.org/10.1016/j.envres.2023.115826
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 3 (WP3) - Sustainable intensification - optimisation at multiple scales
Publisher's version
Supplemental file
Copyright license
Output statusPublished
Publication dates
Online01 Apr 2023
Publication process dates
Accepted31 Mar 2023
PublisherAcademic Press Inc Elsevier Science

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