To reduce the impact of droughts and increase the resilience of regional water systems, various demands, such as hydropower, supply and irrigation, need to be reconciled. In this perspective, designers and practitioners must be able to use information tools to define the hydrological constraints for a sustainable management of the resource. In this work, a web-based open-source geoinformation system is presented, that allows to estimate Flow Duration Curves (FDCs) in ungauged basins. The regional statistical model used, developed by Ganora et al., 2013 [1] in North-Western Italy, is based on the characterization of the FDC in a parametric framework where parameters depend on topographic, climatic, land use and vegetation descriptors computed at the basin scale. The software tool, accessible both by web browsers and GIS desktop (e.g. QGIS), pilots the estimations steps by computing the spatial descriptors and applying relations needed to estimate the full FDC via Burr distribution. The developed server-side scripting provides users with always updated data and procedures, being free from software client compatibility issues.