Observations and modeling of mixing processes in a fresh water reservoir - Valle de Bravo (Mexico)

Current understanding of small-scale physical processes, such as mixing, in tropical water bodies is lacking and observations are scarce at best. This study sheds more light on these processes through a combined observational-modeling approach. For this purpose, observations were made in Valle de Bravo's freshwater reservoir, about 100 km west of Mexico City and at an elevation of 1830 m above sea surface. Turbulence kinetic energy dissipation (TKED) rates were estimated by fitting a theoretical Batchelor spectrum to the temperature gradient spectrum. From similarity scaling of dissipation rates, it was found that in the surface layer, winds were the main driving force in generating turbulence during the day, while convective forces were responsible during the night. Bottom boundary layer (BBL) mixing was mainly driven by internal wave (first vertical and first horizontal mode) breaking at the bottom. Lognormality of turbulence dissipation rates is also discussed for surface, intermediate and bottom boundary layers. For our modeling efforts, a state-of-the-art one-dimensional turbulence model was used and forced with the observed surface meteorology to obtain simulated temperature and dissipation rate profiles. The model results were found to be in good agreement with the observations, though minor differences in dissipation rates were found in the vicinity of the thermocline and the BBL.