Seasonal scale modeling of river inflows in stratified reservoirs: Structural vs. parametric uncertainty in inflow mixing

The extent to which vertical transport in reservoirs is accurately represented by one-dimensional (1D) lake models is linked to the quality of the algorithms representing the fate of inflows. Recent findings suggest that gravity currents in stratified environments not only entrain ambient water but they also detrain water as they flow down-slope. Here, we analyze whether the differences between the entrainment and the entrainment-detrainment approaches of river inflow mixing implemented in 1D models could affect the seasonal-scale simulations of vertical transport in a reservoir. We demonstrate that the structural uncertainty associated with using different inflow modeling paradigms is statistically significant in terms of temperature and salinity predictions, as well as phosphorous loads available to the lake surface; and is of similar order of magnitude as the parametric uncertainty errors arising from the unknown value of model parameters and forcing.