Groundwater Vulnerability Mapping and Ancestral Systems of Water Galleries (Porto Urban Area, NW Portugal): A Design on Nature-Based Solutions

Groundwater resources are crucial to the settlement of populations, and their quantity and quality are essential to the development of urban areas. In fact, nature-based solutions for water were considered in many places using ancestral systems of water galleries and springs to supply urban areas. That design based in natural solutions had proven during centuries to be much less demanding and resourceful. A multidisciplinary approach was applied in Porto urban area (NW Portugal), to assess the urban groundwater supply and ancestral network of water galleries and springs. The infiltration potential index in urban areas (IPI-Urban) is dependent on several parameters (e.g. lithology, structure, weathering grade, morphotectonics, land use, drainage, slope, rainfall, anthropogenic and urban hydraulic features, like the water supply, the sewer and the stormwater networks) which can be overlapped and cross-linked in a GIS environment. Moreover, several vulnerability indexes (DRASTIC, GODS, DRASTIC-Fm, SINTACS and SI) were outlined within a combined approach, and an evaluation of urban recharge was performed. All these permitted to improve the hydrogeological conceptual model for Porto urban area. Therefore, those old underground structures could be a positive asset as socio-economic, environmental and heritage drivers if are used nature-based solutions and good geoethical practices.