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Pesticide forecasting for drinking water quality risk management

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It is approaching the time of year when we start to think about forecasting the usage of pesticides in the next growing season for our water utility clients. UK Regulations (e.g. The Water Supply (Water Quality) Regulations 2016 for England and Wales) require water companies to develop pesticide monitoring strategies for their raw water based on risk. Individual pesticides should be included in these monitoring programmes on the basis of their properties and usage in the drinking water catchment. Expert forecasting of pesticide usage is the best way to ensure that this obligation is met and that the most effective use is made of monitoring resources. The ADAS Predictive Pesticide Risk Assessment and Alerting Service enables water companies to take an informed risk-based approach to their monitoring and keeps them abreast of any changes in usage patterns throughout the seasons.

Pesticide forecasting for drinking water quality risk management

Forecasting pesticide usage

The use of pesticides in agriculture is very dynamic. There are a huge range of products on the market, with new ones being added and old ones being removed every year. Approvals for active ingredients are also continually changing and the legislative environment is very complex. Changes in weather, cropping and markets can have a considerable effect on the level and timing of usage of agricultural pesticides. To keep up to date with these changes locally and to enable us to provide the best possible forecasts, we interact with BASIS qualified advisors working with farmer across major arable and horticultural crops within many of the counties of England and Wales. These advisors provide us with data on cropping plans, changes in practice and key pesticide use changes at least twice every year. We consult with research scientists within ADAS to identify new chemistry and the most common programmes for crops in different parts of the country. We also consult with key agronomy distributers and manufacturers and carry out desk research to identify new products and actives, when they will become available and how they will be marketed. These data sources are turned into county-level forecasts of cropping patterns and pesticide usage by crop for the coming season(s). Cropping and pesticide usage forecasts are distributed onto a 1km grid based on a spatial dataset of land cover previously developed by ADAS (Comber et al., 2008).

Modelling relative risk

The relative rates and areas of usage of agricultural pesticides in a catchment are not the only factors influencing the risk of a pesticide being present in detectable concentrations in raw water. The properties of the pesticide active ingredients, the physical attributes of the soil and the underlying geology, the local climate, the method of application of the pesticide and the growth stage of the crop are also important factors that together determine the likelihood of a pesticide reaching a water body. The predicted concentrations of pesticides in surface water run-off from fields and in groundwater bodies are estimated using simple models that incorporate all of these factors. Outputs from the models at 1km grid cell resolution are used to provide catchment-scale seasonally-specific forecasts of pesticide risk in surface and groundwaters for water companies.

What are the benefits of this service?

The ADAS Predictive Pesticide Risk Assessment and Alerting Service provides an expert-informed prediction of pesticide concentrations and the likely timing of these concentrations to enable water companies to target the highest risk pesticides as part of their water quality monitoring strategy. The insight that is gained into current and future changes to pesticide usage also help inform the planning of the next year’s water quality monitoring and analysis. Update reports at peak application times in the cropping season are used to provide water companies with advance warning of new pesticide formulations and active ingredients to enable them to develop effective methods to test and remove these contaminants from drinking water. Armed with the latest knowledge on this fast-moving industry, water company catchment officers are also better able to promote safe and effective pesticide use to targeted user groups.

If you would like to know more, please contact Lucy Wilson:


Comber, A. Procter, C. Anthony, S. 2008. The Creation of a National Agricultural Land Use Dataset: Combining Pycnophylactic Interpolation with Dasymetric Mapping Techniques. Transactions in GIS. 12(6): 775–791

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