GAIN is a project in collaboration with De Watergroep and KWR which focuses on infiltration of rainwater flowing from impermeable surfaces (e.g. roofs and roads) in protection zones around drinking water production wells. As the practice of increased infiltration is encouraged in Flanders to mitigate the impacts of droughts and flooding events, also regulations on infiltration in drinking water protection zones are changing. Therefore, this project assesses both quantitative and qualitative impacts of rainwater infiltration on groundwater in protection zones.