A landmark event to celebrate the achievement of the GWF Founding Program Director and Canada Excellence Research Chair in Water Security, to develop international strategy for GWF, and to develop vision and identify grand challenges in the field of hydrology of societal relevance. The symposium reflected on developments in hydrology, science and practice over the last 40 years, and projections of future directions for the next 40 years. Thirty-five leading international scientists shared their vision and provided valuable feedback to further the GWF international agenda.