Mixing of an interflow into the ambient water of Lake Iseo

Abstract

River water flowing as an interflow was investigated using field data, collected in Lake Iseo (Italy), and theory. A theory for the lateral falling mechanism of plunging was developed for inflows when the initial densimetric Froude number (Fr 0 ) is slightly larger than unity. The ratio of the river width to the offshore extent of the plunge region was equal to Fr 0 . The mixing ratio in the plunge region was 0.06. Theoretical results were quantitatively consistent with the length scale and mixing ratio of the observed plunge region. The progression of the inflow was interpreted as: initially a laterally falling plunge region with little mixing; followed by a steep underflow region with substantial mixing; and finally an intrusion. The intrusion was at first controlled dynamically by an inertiabuoyancy force balance. Further from the liftoff point, turbulent mixing effects dominated over those due to inertia. Ultimately, the intrusion diffused into the adjacent layers in such a way that the interflow fluid was effectively indistinguishable from the lake water.

Study of tributary inflows in Lake Iseo with a rotating physical model

“…Although already suggested by Bonomi and Gerletti (1967), who underlined the study of the circulation mechanics of this lake as a priority, only recently a set of experimental and modelling activities have been accomplished to specifically investigate its internal hydrodynamics (Pilotti et al, 2013), with a focus on the internal wave structure (Valerio et al, 2012;Vilhena et al, 2013) and on plunging at the entrance of the Oglio River (Hogg et al, 2013). Beside the internal movements triggered by the wind, inflows-induced currents are also central to the understanding of oxygenation, deep-water renewal and nutrient transport in deep lakes.…”

Long-term trends of chemical and modelled photochemical parameters in four Alpine lakes

“…In Lake Iseo, the horizontal length scale of the inlet water intrusions (Oglio River and Italsider Canal) is important from a biological perspective because it is the length scale over which the inflow's potential energy transports nutrients and allochthonous DOC. This length scale is of the order of 4 km as supported by both, conductivity measurements and calculations based on the intrusion dynamics (Hogg et al, 2013).…”

Contribution of extreme meteorological forcing to vertical mixing in a small, shallow subtropical lake

“…The impact of typhoon-induced inflow was large although the inflow effect is usually minor in physical processes in large lakes (Michalsky and Lemmin, 1995). For understanding localized mixing for stratified water bodies, numerous spot measurements are necessary to reveal more precise characteristics of inflow-induced vertical mixing in specific areas with density plume phenomena (Laborde et al, 2010;Hogg et al, 2013). The overall suggestion is that the inflow had an important effect on vertical mixing although wind shear stress was also influential.…”