River Corridor Hydrology
Scientific needs and challenges
Hydrological exchange flows, defined as vertical and lateral flows that bring water from the fast moving main channel to slowly moving permeable stream beds, are the primary control of water quality, nutrient dynamics, and ecosystem health in dynamic river corridor systems, and thus necessitate a more accurate prediction for better water resource management and environmental protection.
However, fully coupled models, which simultaneously simulate the relatively fast stream water, slowly moving groundwater, and their interactions in the hyporheic zone, have not yet been developed for large-scale (10s km scale) rivers over long-term periods (a couple of years) due to low computational efficiency in solving fast and slow flows in one system.
Instead, the one-way coupling concept, which simulates surface water and groundwater separately, is more practical and commonly used for large-scale rivers over long time periods. However, high uncertainties existed in both surface and groundwater models because the boundary conditions at the river bed (and in the hyporheic zone) for both models are usually unknown. Despite other uncertainties in groundwater models, we argue that achieving more reliable boundary conditions, such as hydrostatic pressure, hydrodynamic pressure, and shear stress, at the river bed is an necessary step for reducing the uncertainties of groundwater models.