Acid herbicide wash-off exploration tool

Acid herbicide wash-off exploration tool. Guidance document.

  • The Acid herbicide wash-off exploration tool can be used to explore the potential impacts of acid herbicide wash-off (i.e. agricultural run-off from grassland) during periods of intense rainfall, on phytoplankton in South West’s estuaries.
  • Using a logic chain risk assessment process, it provides a simple, high-level risk-assessment approach and is easily adaptable to incorporate new catchments, chemicals and future scenarios.
  • The MS Excel spreadsheet tool is available on request from Dr Ross Brown (
  • The Guidance Document sets out details of the tool.
> Download the full Guidance Document

Application of the ‘Acid herbicide washoff exploration tool’ to the South West’s estuaries

  • This report outlines a high-level risk assessment undertaken to understand the scale and trajectory of mobilised acid herbicides (i.e. agricultural run-off from grassland) during periods of intense rainfall, and their impacts on phytoplankton within five of the South West’s estuaries (Camel, Clyst, Exe, Kenn, Taw & Torridge).
  • Computational tools quantifying contaminant run-off throughout river catchments have a key role to play in the management of agricultural land and river water quality. We trialled a whole catchment approach to evaluate acid herbicide wash-off in rivers and estuaries in SW England. Our results indicate that improving soil quality (carbon content and water infiltration capacity e.g. through cover cropping) is not only likely to benefit crop yield, but also reduce peak (first flush) herbicide concentrations in these water bodies from 60% to >500% depending on baseline soil quality.
  • This analysis was developed under the NERC-funded South West Partnership for Environmental and Economic Prosperity programme (SWEEP) and, specifically, its project on Water Quality and Aquaculture which seeks to evaluate the effect of water quality on the viability of bivalve aquaculture in South West England’s estuaries.
  • The report [Application of the ‘Acid herbicide wash-off exploration tool’ to the South West’s estuaries. Report assessing the risk to estuarine phytoplankton from agricultural run-off from grassland] is available on request from Dr Ross Brown (

Published: November 2021
Dr James Webber, SWEEP, Impact Fellow
Dr Ross Brown, SWEEP, Impact Fellow
Dr Nick Paling, Westcountry Rivers Trust, Head of Evidence
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