Abstract
AbstractRecent years have seen the development of 1‐D and 2‐D regional‐scale hydrological‐hydrodynamic models, which differ greatly from reach‐scale applications in terms of subgrid assumptions, parameterization, and applied resolution. Although 1‐D and 2‐D comparisons have already been performed at reach and local scales, model differences at regional scale are poorly understood. Moreover, there is a need to improve the coupling between hydrological and hydrodynamic models. It is addressed here by applying the MGB model at 1‐D and 2‐D dimensions for the whole ~700,000 km2 Negro basin (Amazon), which presents different wetland types. Long‐term continuous simulations are performed and validated with multisatellite observations of hydraulic variables. Results showed that both approaches are similarly able to estimate discharges and water levels along main rivers, especially considering parameter uncertainties, but differ in terms of flood extent and volume and water levels in complex wetlands. In these latter, the diffuse flow and drainage patterns were more realistically represented by the 2‐D scheme, as well as wetland connectivity across the basin. The 2‐D model led to higher drainage basinwide, while the 1‐D model was more sensitive to hydrodynamic parameters for discharge and flood extent and had a similar sensitivity for water levels. Finally, tests on the coupling between hydrologic and hydrodynamic processes suggested that their representation in an online way is less important for tropical wetlands than model dimensionality, which largely impacts water transfer and repartition.
Highlights
The 2‐D model led to higher drainage basinwide, while the 1‐D model was more sensitive to hydrodynamic parameters for discharge and flood extent and had a similar sensitivity for water levels
The basin is divided into unit‐catchments using a fixed‐length, vector‐based discretization (Siqueira et al, 2018), which in turn are divided into hydrologic response units (HRUs) where vertical hydrological processes as canopy interception, evapotranspiration, and soil infiltration are considered to model the generation of surface, subsurface, and groundwater flows
Our results show that 1‐D and 2‐D models respond differently for each wetland type, while 1‐D and 2‐D models had similar performance for flood extent and volume, discharges, and water levels in the Negro mainstem, the main difference related to the interfluvial wetlands. 1‐D models are developed for river floodplains, and they are expected to be sufficient for large‐scale in‐channel river hydrodynamics only (Schumann et al, 2013)
Summary
Recent years have seen the development of regional‐ to global‐scale river hydrodynamic models at increasing resolution, using either the full Saint‐Venant equation or its simplifications (diffusive and local inertia) and adopting either 1‐D or 2‐D schemes (Bates et al, 2018; Dottori et al, 2016; Falter et al, 2016; Getirana et al, 2017; Mateo et al, 2017; Paiva et al, 2013; Paiva et al, 2011; Pontes et al, 2017; Sampson et al, 2015; Schumann et al, 2016; Yamazaki et al, 2013; Yamazaki, Sato, et al, 2014). Intercomparison projects between global models have showed the necessity of improving routing schemes with hydrodynamic modules (Zhao et al, 2017) and the potentiality of continental 1‐D models with floodplain modules to represent large‐scale flooding (Trigg et al, 2016). In this latter, a case study in the African continent showed relevant discrepancies between models in large deltas and arid/semiarid wetlands (Trigg et al, 2016), which frequently present complex 2‐D hydrodynamic flow patterns
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