Retention time and dispersion associated with submerged aquatic canopies

摘要: [1] The shear layer at the top of a submerged canopy generates coherent vortices that control exchange between and overflowing water. Unlike free layers, in do not grow continuously downstream but reach maintain finite scale determined by balance production dissipation. This defines length vortex penetration into canopy, δe, region rapid overflow. Deeper within transport is constrained smaller turbulence scales. A two-box model proposed on basis δe. Using diffusivity rates defined previous studies, predicts timescale required to flush through vertical over range density height. The predicted retention times, which from minutes an hour, are consistent with inferred tracer observations field comparable times for some hyporheic regions. exchange, along in-canopy velocity, determines minimum dominates water renewal. Shorter canopies renew interior longitudinal advection. Finally, influences dispersion transient storage process. When controls retention, increases advection renewal, patch length.