Our understanding of hydrological systems enables decision-makers to respond to rapidly evolving issues of water security and water quality. Stable, radioactive, and radiogenic isotopes, trace elements, and noble gases are routinely utilized within the hydrologic sciences to quantify subsurface flow paths, sources, residence times and reactive processes. New analytical techniques, experimental designs, and modeling approaches that incorporate chemical signatures can more accurately resolve the coupled structure of fluid transport and solute transformation across a broad range of scales. This session invites presentations that highlight new and diverse applications of innovative tracers in field systems, laboratory experiments and numerical models. We welcome studies that provide new insights into the connections between hydrology, ecology, and reactive solute transport. We encourage presentations that seek to gain new insights in critical zone processes of understudied systems such as intermittent or ephemeral streams, interconnected or managed surface water-groundwater systems.