The dataset Hydro-CH2018 reservoirs provides estimates of current and future water supply, water demand, and storage volumes for 307 medium-sized catchments in Switzerland. Water supply for current (1981-2010) and future (2070-2099) climate conditions was simulated using the hydrological model PREVAH. For modeling current water supply, observed meteorological time series were used as input, while simulated meteorological time series derived from 39 model chains of the CH2018 initiative were used as an input for simulating future climate conditions. Water demand was estimated for six categories: - 1) Drinking water (households and tourism), - 2) industry (second and third sector), - 3) artificial snow production, - 4) agriculture (irrigation and livestock feeding), - 5) ecology (residual flows), and - 6) hydropower. Future estimates consider changes in demand related to population growth and changes in the hydrological conditions. Storage volumes are provided for natural lakes (storage capacities and usable volumes), artificial reservoirs, reservoirs for artificial snow production, and drinking reservoirs. A detailed description of the simulation and estimation procedures can be found in * Brunner, M.I., Björnsen Gurung, A., Zappa, M., Zekollari, H., Farinotti, D., Stähli, M., 2019. Present and future water scarcity in Switzerland: Potential for alleviation through reservoirs and lakes. Sci. Total Environ. 666, 1033–1047. https://doi.org/10.1016/j.scitotenv.2019.02.169. This dataset contains the following information: 1. Shapefile with the 307 medium-sized Swiss catchments. 2. Textfiles with the water supply simulations for the control run and the 39 climate model chains (one file per chain) at daily resolution for the 307 catchments. 3. Textfiles with the current and future demand estimates per category at monthly resolution for the 307 catchments. 4. Textfiles with the storage volumes per category and catchment.