Analysis of possibilities for rainwater harvesting from green roofs as a part of sustainable water management in Lithuania

Abstract Europe faces extreme climate change; these changes are fixed as longer drought periods, not just in springs or the middle of summer but all over the vegetation period. Long droughts mean water shortages in rural areas, reduced river water flows, and limited opportunities to use this water for irrigation. Attention should be paid to different rational water management technologies and systems with particular emphasis on rainwater harvesting. Sustainable development goals targeted for the water sector in Lithuania can be reached underwater by harvesting from roof systems using water tanks or harvesting rainwater in green roof systems. One method meets farmers’ requirements, another - sustainable development goals. Lithuania is in a zone of excess moisture, and by accumulating this water, it is possible to compensate for the lack of water reserves in topsoil in the dry season. This study aims to investigate how water can be storage in green roof structures. The investigation runs as field experiment study, when the dynamics of rainwater runoff from an experimental green and bituminous roof was recorded in 2021-2022 two 1 m 2 stands were affected by open field climatic conditions. Meteorological data were obtained from the Kaunas City meteorological station. The study confirms that a green roof can reduce the load on rainwater systems and retain precipitation in the green roof layers. Study confirms that rain retention from the green roof varied from 58.8, % to 46.8, % in October and November and from 26, % to 34, % in the winter period, when there was fixed frost and snow cover. From bituminous tile the retention rate warried from 6-45 %.