Effects of dimensionality on the performance of hydrodynamic models

Abstract

Abstract. Numerical models are an important tool for simulating temperature, hydrodynamics and water quality in lakes and reservoirs. Existing models differ in dimensionality by considering spatial variations of simulated parameters (e.g., flow velocity and water temperature) in one (1D), two (2D) or three (3D) spatial dimensions. The different approaches are based on different levels of simplification in the description of hydrodynamic processes and result in different demands in computational power. The aim of this study is to compare three models with different dimensionality and to analyze differences between model results in relation to model simplifications. We analyze simulations of thermal stratification, flow velocity, and substance transport by density currents in a medium-sized drinking water reservoir in the subtropical zone, using three widely used open-source models: GLM (1D), CE-QUAL-W2 (2D) and Delft3D (3D). The models were operated with identical initial and boundary conditions over a one-year period. Their performance was assessed by comparing model results with measurements of temperature, flow velocity and turbulence. Results show that all models were capable of simulating the seasonal changes in water temperature and stratification. Flow velocities, only available for the 2D and 3D approaches, were more challenging to reproduce, but 3D simulations showed closer agreement with observations. With increasing dimensionality, the quality of the simulations also increased in terms of error, correlation and variance. None of the models provided good agreement with observations in terms of mixed layer depth, which also affects the spreading of inflowing water as density currents, and the results of water quality models that build on outputs of the hydrodynamic models.

Physical mechanisms of internal seiche attenuation for non-ideal stratification and basin topography

“…S8), demonstrating that Delft3D is capable of reproducing heat transport and hydrodynamics of the stratified reservoir. This result confirms previous studies that have successfully applied hydrostatic models to simulate large-scale flow features, including internal seiches in stratified lakes and reservoirs (Laval et al, 2005;León et al, 2005;Dissanayake et al, 2019;Ishikawa, Gonzalez, et al, 2021).…”

“…4a). A detailed model validation is presented in the supplementary information and has also been performed by Ishikawa, Gonzalez, et al (2021).…”

Reconsideration of wind stress, wind waves, and turbulence in simulating wind-driven currents of shallow lakes in the Wave and Current Coupled Model (WCCM) version 1.0

“…Although the WCCM performance has been improved relative to the reference models of the EFDC, LCM_1, and LCM_2, the correlation between WCCM-simulated and ADP-measured current speed remains low, and the mean of the simulated current speed is lower than that of the measured current speed. Similar conclusions can be drawn from the model validation studies in other lakes (Huang et al, 2010;Jin et al, 2000;Ishikawa et al, 2021;Soulignac et al, 2017). There are three possible explanations for this problem.…”