The environmental monitoring of pesticides is conducted primarily in four small catchments (8-16 km2), each representing a major agricultural region in Sweden. The catchments are situated in Skåne (M42), Halland (N34), Östergötland (E21) and Västra Götaland (O18). The areas are referred to as model catchments because they can be viewed as representing typical areas within each region. All four catchments are comprised of ca 90% arable land. Within each model catchment, surface water and sediments are sampled within the stream that drains the area, and groundwater is sampled from 3-6 meters depth. The farmers within the model catchments are interviewed each year to collect information about the crops that are being grown and which pesticides are being used. The reported pesticide usage is compared to the pesticide occurrences detected in the surface water that drains the area. Based on this data, the loss of pesticides from arable land is calculated.
The environmental monitoring program also includes surface water and sediment sampling in two larger streams/rivers in Skåne (Skivarpsån and Vege å, with catchments of 102 and 488 km2, respectively).
Pesticides in precipitation (since 2002) and air (since 2009) are collected at Söderåsen in Skåne (Vavihill/Hallahus). Since 2009, precipitation was also collected at Aspvreten outside Nyköping. This location has now been replaced by Norunda, north of Uppsala, since 2017.