Water transit times and flow pathways are crucial elements in characterizing catchment hydrologic response. Understanding their variability in space and time sheds light on the link between discharge formation and water quality at the catchment scale. Here, we introduce a novel modeling framework to explore water transport mechanisms using the Hafren catchment in Wales (UK) as a case study. We show that a fully distributed hydrological model coupled with a transport component for conservative tracers is useful in analyzing how hydrometeorological conditions and spatial heterogeneity may affect water transit times and age distributions in a real catchment. We use the model to track the paths of water parcels that entered the catchment as rainfall over 2 years, labeling each day of rain individually. There is a reasonable agreement between tracer simulations and observations, suggesting that dynamic transit time distributions (TTDs) both forward and backward in time can be approximated using a high spatial and temporal resolution hydrochemical model, without assuming a priori any transit and storage selection functions at the catchment scale. TTDs are quantified for the modeled internal dynamics of the study catchment. TTDs conditional on a given rainfall time are mostly correlated to the season in which the rain event occurs, whereas TTDs conditional on a given exit time are mostly affected by catchment wetness. When TTDs for individual rainfall events are re‐scaled as functions of cumulative discharge, they collapse around a single common distribution, suggesting a potential characteristic catchment function.

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Concerns over water scarcity, climate change, and environmental health risks have prompted some Asian cities to invest in river rehabilitation, but deciding on the end goals of rehabilitation is a complex undertaking. We propose a multidisciplinary framework linking riparian landscape change to human well‐being, providing information relevant to decision makers, in a format that facilitates stakeholder involvement. We illustrate this through a case study of the densely settled, environmentally degraded, and flood prone Ciliwung River flowing through metropolitan Jakarta, Indonesia. Our methodology attempts to respond to this complexity through an iterative approach, strongly based on conceptualization and mathematical modeling. Nested hydrologic, hydrodynamic, and water quality models provide outputs at catchment‐, corridor‐, and localized site‐scales. Advanced 3‐D landscape modeling is used for procedural design and precise visualization of proposed changes and their impacts, as predicted by the mathematical models. Finally, participatory planning and design methods allow us to obtain critical stakeholder feedback in shaping a socially acceptable approach. Our framework aims at demonstrating that a change in paradigm in river rehabilitation is possible, and providing future scenarios that balance concerns over flooding, water quality, and ecology, with the realities of a rapidly growing megacity.