Comparison Between Two Hydrodynamic Models in Simulating Physical Processes of a Reservoir with Complex Morphology: Maroon Reservoir

Behnam Zamani,Manfred Koch

doi:10.3390/w12030814

Abstract

Two 3D hydrodynamic models, AEM3D and MIKE3, are compared in simulating hydrodynamics of the Maroon Reservoir in southwest Iran. The reservoir has a complex bathymetry with steep walls, which makes it a good case for studying the performance of hydrodynamic models. The models were compared together and with measured water temperatures from different locations of the reservoir in a five-month period between December 2011 and April 2012. The results indicated that the AEM3D model, which uses a finite difference scheme with a purely z-level vertical discretization, showed better consistency with observations so that the AME and RMSE of the model remain below 1 °C. The MIKE3 model showed overall higher errors from 56% to 130% larger than AEM3D and the level of error strongly depends on its vertical discretization method and the turbulence model. The lowest errors by MIKE3 were seen by the k-ε turbulence model with a hybrid z-sigma discretization, while the highest errors were generated by using the sigma vertical discretization. The vertical mixing model in AEM3D model, used instead of the constant eddy viscosity or k-ε formulation, showed a better performance in modeling vertical mixing and wind mixed layer, which is another reason of observing better results by this model than MIKE3. Overall, this study shows AEM3D as a more appropriate model for simulating deep and complex reservoirs with steep slopes and walls.

Highlights

Dam reservoirs are man-made lakes which, having nearly half of the characteristics of natural lakes [1], possess their own distinct characteristics in many other aspects
The hydrodynamics obtained with the AEM3D and three variants of the MIKE3 model are illustrated and compared to each other over the five-month simulation horizon
Our study shows that both AEM3D and MIKE3 models simulate the hydrodynamics of the Maroon Reservoir with errors in a reasonable range and the results are not significantly different from the observed data

Summary

Introduction

Dam reservoirs are man-made lakes which, having nearly half of the characteristics of natural lakes [1], possess their own distinct characteristics in many other aspects. Hydrodynamic processes dictate stratification and mixing in lakes and reservoirs that, in turn, control the temporal and spatial distribution of nutrients and dissolved oxygen [2,3,4]. The importance of the numerous physical processes in reservoirs necessitates a deep understanding of their intricate mechanisms which, mostly, can only be achieved by advanced numerical modeling, allowing to investigate and to predict their responses to changes imposed on their environment. Hydrodynamic models are the tools to simulate the behavior of water bodies under various forcing conditions. These models are implemented with one-, two- and, nowadays increasingly, three-dimensional numerical schemes which solve spatially and temporally the differential equations describing water transport, advection and dispersion and other processes, driven by physical and climate conditions of the modeled lake

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