The Protect-Streams-4-Sea project focuses on a joint environmental monitoring of nonpoint source pollutants and litter that end up in the Black Sea. This is a main priority of the Black Sea Programme and essential, because once the enclosed Black Sea is polluted, it is very difficult to depollute. Most cleaning efforts focus on the sea itself or along the coastal areas. The watersheds that end in the Black Sea have not been focal points despite providing many of the pollutants and litter. A similar example is the Mississippi Basin that transports the pollutants that have created the dead zone in the Mexico Gulf. The idea of this project is to stop the nonpoint source pollutants and litter from reaching the streams and rivers and consequently not reaching the Black Sea. If successful, this can cost-effectively maintain a clean Black Sea that will benefit the welfare of the entire region. This will be achieved by using innovative methods (fingerprinting) to correlate landscape position with the pollutants in the stream water and bed. Soil samples will be taken along stream banks, soil surfaces and in-stream. This way the origins and the contributions of sediment and other nonpoint source pollutants to the stream water and bed will be estimated. The origins could be the stream banks (e.g. steep, non-vegetated, etc.) or soil surface with different land covers (e.g. burnt areas, flooded areas, forests, degraded or specific crops). In addition, traditional (erosion pins, runoff plots) and new innovative (remote sensing, indices and drones) methods will be used for the pollutant estimations. Hydrologic models will be applied to simulate the pollutants at the watershed scale based on the project data from the fingerprinting method and the stream bank and bed and soil surface plots. A Multi-Criteria Decision Analysis and a Decision Support System will be developed to find the “hot spots” and recommend best management practices in each pilot area. Hot spots are the areas that contribute most pollutants and/or litter. The recommended practices will be nature-based and applicable to the entire region. The final part will develop and/or test innovative tools/machines: 4 litter traps (in Armenia, Greece, Moldova and Turkey) and 1 skimmer vessel (in Romania) in the pilot area water bodies to collect litter and other pollutants. The pilot areas will be in five different Black Sea countries allowing to test the tools and methods in different environments representative of the region. This should help the tools and methods adoption by all Black Sea countries and lead to a joint monitoring program for inland nonpoint source pollutants and litter. With Universities, NGOs and public authorities partnering on this project the methods and tools developed will be science-based and practical. Finally, numerous and diverse communication activities will help reach all target groups and lead to the adoption of these joint monitoring methods and tools in the region.