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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 on computational power. The aim of this study is to compare three models with different dimensionalities 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 1-year period. Their performance was assessed by comparing model results with measurements of temperature, flow velocity and turbulence. Our 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.

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.

Fluvial systems are endowed with features such as heterogeneity and variability which allow the classification of a fluvial landscape. Rapid assessment protocols have been useful tools for the characterization of integrity, especially in river segment scale. The objective of this paper was to apply three protocols in order to evaluate their performance in comparison with each other and with the results obtained by analytical methods of water quality 86 Jucimara Andreza Rigotti et al.

Nature-based solutions for managing the urban surface runoff: an application of a constructed floating wetlandUrban surface runoff strongly contributes to the degradation of river ecosystems. Innovative and nature-based solutions have been applied to face such environmental problems. In this regard, constructed wetlands -a low-cost green treatment technology -represent a successful example of a solution that results in social and environmental benefits. Constructed floating wetlands (CFW) is a relatively new water treatment technique that consists of emergent macrophytes planted on floating structures. The CFW has been tested for the treatment of wastewater and stormwater runoff. However, few studies assess the system's capability over short periods of retention time and its performance under hydraulic shock-loading. This research reports the performance of CFW applied to treatment of simulated urban surface runoff. The removal efficiency of total nitrogen (TN) and total phosphorus (TP) was investigated for two macrophyte species: Typha domingensis and Schoenoplectus californicus. Total organic carbon, wet biomass, chlorophyll-a, dissolved oxygen (DO), pH, oxygen reduction potential (ORP), conductivity, temperature and turbidity were also measured. A commercial floating structure without growth medium was employed. The experiment utilized batch mesocosms, first with a seven-day retention time and second, under hydraulic shock-loading with 24, 2, and 4 h retention times. Differences between treatments and controls were analysed by PERMANOVA and ANOSIM tests. The results for a seven-day batch indicated that T. domingensis was more efficient than S. californicus (removal efficiency of TP = 47 %, TN = 78 % and TP = 11 %, TN = 30 %, respectively). There was a significant difference in nutrient removal for retention times of 24 h and 4 h for T. domingensis. No significant nutrient removal was noticed for S. californicus when the retention time was less than seven days.