The aim of this research is to study the separation possibilities of household and rainwater sewage collectors in Riga. The performance of sewage pumping stations on the right and left banks of the Daugava River during the dry periods and those of rainfall is analyzed as well as the yearly costs of electric energy are given. This paper analyses the costs that would rise with re-building of the central regional co-system into the separated one. The locations are shown where the rainwater collectors are connected to the household sewage collectors likewise the recommendations are given for the separation of these collectors.

Newly constructed buildings are subject to stricter requirements – the building must not harm the environment, they must be energetically and economically efficient, comfortable, ecological, etc. One such green energy-saving idea is green roofs and walls of buildings. The purpose of this study is to determine the dynamics of rainwater runoff under real natural conditions, in a typical green roof construction, compared to runoff from a roof covered with bituminous tiles. The study was conducted in the year 2022–2023 by installing two 1 m² stands, which are affected by real climatic conditions. One stand was covered with traditional bituminous tiles, but the other was covered with a ‘green roof’ coating. Meteorological data were obtained from the Kaunas City meteorological station. During the first months of observation, it was possible to record the tendency that rainwater runoff is slow in the case of a green roof, but it continues even after the intense rain has ended. Analyzing the data, it was found during the research that the regression coefficients are very small in assessing the relationship between average daily temperatures and runoff in individual months, R2 – 0.0453 to 0.0553. The study showed that under certain meteorological conditions, a green roof can accumulate up to 35–45 percent more water than a roof covered with bituminous tiles. This means that the water is accumulated and then slowly drains into the rain collection systems.