Polluted surface waters that infiltrate into adjacent aquifers can impair groundwater quality. Contaminated groundwater discharging into streams, lakes, wetlands or the ocean can compromise their water quality. Indeed, various types of groundwater-surface water interactions and related processes can spread pollution across such boundaries or even remedy it. And we want to hear all about it, and the factors affecting it, from both sides of the groundwater-surface water interface (hydrogeology – hydrology disciplines), in this joint CGU/IAH-CNC session. Pollutant sources can encompass anthropogenic contaminants or be natural in origin (nutrients, metals, salts, etc.) where human activity has thrown things out of balance, and include legacy or emerging contaminants. Impacts on drinking water supplies and on ecosystems (aquatic or terrestrial), and attenuation processes active within the transition zone (between groundwater and surface water) are especially of interest. Studies on assessing the challenges and mechanisms to actively managing or remediating these pollutants (using gw-sw interaction related approaches) are most welcome.