Unrealized potential for small and micro hydropower generation exists in Europe's thousands of historical hydro sites. However, the evaluation of possible hydro sites requires large amounts of data. Historical hydro sites are mostly located in mountainous and rural areas that are most of the times poorly gauged. Accordingly, feasibility studies of the possible hydro sites in such areas are difficult, costly, and time intensive. This paper presents a methodology for a large-scale preliminary evaluation of possible historical hydropower sites in poorly gauged areas. The developed methodology automates the estimation of the main required parameters for the evaluation of each hydro site in a geo-information system (GIS). The core of the methodology is a fully spatially distributed continuous hydrological model embedded in the GIS, which estimates streamflow values at every point of the drainage network. Simultaneously the system automates the estimation of other important parameters like expected head, environmental sensitivity, grid connections etc. The results of this study highlight the ability of the developed methodology to provide the data required during the inception phase of small hydropower development planning in a cost and time efficient manner. Thus, expensive ground investigations are limited to the most promising sites for hydropower development. (C) 2016 Elsevier Ltd. All rights reserved.