Pseudo two‐dimensional simulations of internal and boundary fluxes in stratified lakes and reservoirs

Abstract

New mixing algorithms to model the vertical mixing processes in stratified lakes have been developed for the Dynamic Reservoir Simulations Model, DYRESM, and have been validated using five lakes of different size, shape and wind forcing characteristics. An analysis of temperature profiles from Lake Kinneret, Canning Reservoir and Mundaring Reservoir, were used to develop a strong inverse relationship between the Lake number and lake‐wide average vertical eddy diffusion coefficient. Analysis of microstructure data collected in Lake Kinneret using the portable flux profiler suggests that the development of a turbulent benthic boundary layer (BBL) accounts for a large proportion of the lake‐wide average vertical flux. A pseudo two‐dimensional model with explicit BBL and internal fluxes was developed based on the Lake Kinneret field observations and similar investigations in the literature. A sensitivity analysis revealed that improvements in the ability of DYRESM to model the diverse range of lakes considered without user‐calibration was attributable to a wind‐sheltering algorithm and a process‐based description of BBL and internal fluxes.

Keywords:

• Eddy diffusion coefficient
• surface mixed layer
• benthic boundary layer
• DYRESM