Since 1999, the municipalities of the Siauliai District in Lithuania and Jelgava District in Latvia have been cooperating in preparation and implementation of joint projects. These municipalities share a common border, which includes the Lielupe river basin. Both project partners are currently faced with the problem of polluted rivers in the Lielupe river basin due to poor waste water treatment that leads to sewage flowing into surface and groundwater. Poor waste water treatment is a barrier for greater biodiversity and the development of water tourism in both districts. Moreover, it adversely affects the inhabitants of the towns of Sauginiai and Vircava. The water supply and sewage treatment systems are being reconstructed in order to bring cleaner water to inhabitants and also make it more cost-effective. This project is a continuation of a previous project entitled “Improvement of water supply services in small settlements of Siauliai, Joniskis and Jelgava districts”, which was partly financed by the Baltic Sea Region INTERREG III B Neighbourhood programme INTERREG IIIA Priority South. Documentation and feasibility studies done for the previous project were used in the implementation of this project. Inhabitants will be provided with services that comply with European Union, Latvian and Lithuanian regulations. Municipality officials in charge of waterworks in both Siauliai and Jelgava will also be able to enrich their knowledge in order to more effectively carry out their duties and work for the good of the local inhabitants and the environment.