It is widely documented that about 80% of the marine litter found in the seas and oceans has a terrestrial origin and that the rivers are one of the main transport ways of pollution from land. Only through the knowledge of the quantities and the phenomena associated with the transport of litter by rivers will be possible to anticipate appropriate mitigation measures. The trans-European RIMMEL project intends to get some answers to the existing gaps of knowledge.

Through the Marine Strategy Framework Directive and various international initiatives (Rio + 20; (G7), the Marine Litter has been recognized as an important issue that requires action, however, the degree of knowledge about their origins is still limited. Some sources cite an indicative value of 80% of the marine waste as having entered into the sea through rivers. It will be expected that the amount of litter is very variable depending on the type of river and the period of the year.

The waste carried by rivers to the sea is originated on land and are transported to the sea simultaneously with the fresh water, natural waste, nutrients and sediment. The component of waste transported that causes problems for marine ecosystems are those that are not biodegradable, many of these materials are plastic, but also they include free glass and metal, although with a smaller visual impact on the surface of the rivers. Images from the bottom of the sea near the mouth of the rivers show that these heavier products remain in the bottom of the sea.

The need to quantify the litter of rivers as major source supplier of litter to the marine environment is recognized. The studies on this subject are still tiny, and the information available is not in many cases comparable. Searching the literature also reveals that there is no ongoing monitoring program for a long period for the litter floating in rivers or in the marine environment. However, there are a number of studies carried out by researchers from outside Europe that show that the pollution by garbage (especially plastic) and which accumulates in the marine environment, mostly originates in land-based sources.

It is possible to anticipate that without mitigation measures, any region with major rivers flowing into the sea will be suppliers of high quantities of litter to the coastal system, however, the size of such inputs remain without systematic quantification.

In 2013 the DG Environment of the European Commission sponsored the project "Identification and evaluation of inputs of litter (Marine) by the rivers". This project aimed to investigate the level of pollution caused by plastic litter in the rivers of the European Union and to estimate the magnitude of the inputs of plastic litter rivers for four regional seas of Europe, the report of this project can be consulted em:

In 2016, was published by the Joint Research Center (JRC) the technical report “Riverine Litter Monitoring - Options and recommendations", prepared by the Technical Group of Marine Litter, which supports Member States (MS) in the implementation of the Marine Strategy Framework Directive (DQEM) )

This technical report will support the MS in the implementation of programs for the monitoring and the planning of measures to reduce marine litter. This report is a compilation of options for monitoring the litter of rivers and for the quantification of waste flows with a focus on anthropogenic litter. It includes the current scientific and technical references about litter in hydrographic systems, his regime of flows and basic properties, also provides recommendations for approaches and methodologies for monitoring.

In November 2015, the JRC has launched an exploratory research project, RIMMEL, “Modeling and Monitoring of environmental loads in rivers of macro litter" in rivers: page=RIMMEL, which will had a duration of 24 months. This project quantifies floating macro litter transported by the rivers to the sea and is aimed at the creation of a trans-European network for monitoring by observation of loads of debris/litter floating in water lines. Portugal participates in this project with some rivers and streams of the region Norte, Centro, Tejo and Oeste and the Algarve.

The leaflet can be consulted at