The overall project objective is to reduce the quantity of contaminants from rain and surface water drained into the Baltic from the south-east part of the Baltic Sea Region. Main activities of the RAINNET I project concern two fields:1) Conception and designing works leading to the preparation of concepts of the development of water management systems, including rainwater drainage in the municipalities of Gdynia, Reda, Rumia and Wejherowo in Poland and Klaipeda in Lithuania, and to the development of technical documentations for investments (for all project partners) connected with the pre-treatment of rain water that are key to the improvement of water purity of Baltic Sea;2) Knowledge sharing and exchange of experience on improving functioning of water management systems in coastal areas of South-East Baltic.