To quantify how much litter is floating down the more than 2,500 rivers flowing into European seas, the EU Commission’s Joint Research Centre (JRC) launched a two-year project, called "RIMMEL" (http://mcc.jrc.ec.europa.eu) in the summer of 2016. The project is currently in progress on more than 50 rivers across the EU.

To monitor the amount of litter floating on the surface of a river, the first step is to establish an elevated location (bridge, quay, etc.) at the river’s estuary (river/sea boundary). Observers record the amount of floating litter at that specific location, weekly or bi-weekly, by performing short monitoring sessions (around 30 minutes). The recordings are done with a mobile JRC app, called the "Floating Litter Monitoring Application", that classifies "macro litter" (bigger than 2.5 cm) into categories including plastic, rubber, textile, paper, wood, metal, other litter and non-litter items such as leaves.

One of the Clean Europe Network (www.cleaneuropenetwork.eu) members, Paisaje Limpio, the Spanish litter prevention association, is measuring floating litter on three Spanish rivers: the Bésos in Barcelona (1.5m inhabitants), the Guadalhorce in Málaga (0.5m) and the Nervión in Bilbao (0.35m) – providing insights into litter patterns of different-sized cities.

The monitoring phase ends in the autumn of this year, when the JRC will compile and analyse the data gathered from across Europe to get a model of the amount of litter entering European seas. Further understanding river litter movement can improve litter prevention efforts, says the Clean Europe Network.