Viral inactivation and adhesion-aggregation in water are often studied as separate phenomena. When the focus is placed on viral adhesion-aggregation, inactivation is neglected because the phenomena under investigation occur over a short period measured in days. When viral inactivation is studied, adhesion-aggregation phenomena are considered to be negligible because viral survival is traced over several days or months. In the present work, we took a global approach, examining the relative contributions of each of these processes in a complex system composed of groundwater, Poliovirus 1, and a hydrophobic container (polypropylene) maintained in a dark environment at 20 degrees C. We demonstrated that infectious viral load fell off 2.8 log(10) during the first 20 days. During this time, adhesion was far from negligible because it accounted for most of the decline, 1.5 log(10). Adhesion was undoubtedly favored by the presence of divalent ions in the groundwater. After 20 days, aggregation may also have been the cause of 0.66 to 0.92 log(10) of viral loss. Finally, viral inactivation was quantitatively the lowest phenomena because it only explained 0.38 to 0.64 log(10) of the viral loss. This study thus clearly demonstrated that estimates of viral survival in a given system must always take into account adhesion-aggregation phenomena which may be responsible for the majority of viral loss in the aqueous phase. Adhesion and aggregation are reversible processes which may lead to an underestimation of viral load in certain studies