Many scientific disciplines address, and societal sectors interact with, various aspects, components, and subsystems of water on land, which together form the terrestrial hydrosphere within the Earth System. Advancing knowledge of this sphere as a coherent, integrated whole requires a consistent and realistic understanding across the water-related domains. Achieving such knowledge convergence requires systematically and synergistically identifying and bridging major gaps across the domains. A network-based standard model is proposed as a foundation for this.