Agricultural water pollution survey, Loddon

Affinity Water asked ADAS to undertake desk-based and walkover surveys to identify potential diffuse and point sources of water pollution.

Background

Water pollution from agricultural sources, particularly Metaldedyhe, is a key issue in the Loddon catchment. The catchment is upstream of a number of Affinity Water’s surface water abstractions from the River Thames.

Affinity Water commissioned ADAS to undertake desk-based and walkover surveys to understand land use adjacent to the watercourse and to identify potential diffuse and point sources of pollution.

Actions

ADAS collated and mapped information on agronomists and contractors working in the catchment. Local farmers were asked a series of questions to verify metaldehyde and other oilseed rape herbicide use.

Following desk studies and postal communication with landowners, ADAS consultants produced an interactive PDF map (i-PDF) for each catchment.

A wet weather walkover survey of 4,372 ha was carried out to identify land use adjacent to the watercourse and potential diffuse and point sources of pollution (‘hotspots’). The walkover survey identified 76 hotspots and 25 features. Each hotspot was categorised for scale and severity of the issue. Photographic evidence was also collected.

Based on the catchment walkover results, ADAS created a GIS layer with colour coding by crop type, as well as locations of pollutant hotspots and ‘other features’, for Affinity Water.

Results

The aim was to increase Affinity Water’s understanding of the Loddon catchment through investigations of agricultural pollution pathways, in order to support future catchment management activities. ADAS successfully identifed potential agricultural pollution pathways and made recommendations for the future management of the Loddon catchment.

On completion of the project, ADAS recommended that further investigations at farm and field level would be required in order to fully understand metaldehyde and OSR herbicide use.