Gravitational Motions in a Large Subtropical Reservoir

Abstract:

Subtropical lakes and reservoirs are characterized by a definite, but moderate vertical thermal stratification, so that vertical mixing is the result of a balance between the surface buoyancy flux and wind stirring and horizontal exchanges are the result of a series of gravitational motions: differential mixing, cooling, heating, and absorption. Here we report on two field experiments carried out in Lake Argyle, Australia’s second largest artificial lake by volume, in May 2012 and November 2013 that illustrate the delicate balance that exists in subtropical lakes between buoyancy and inertia and how this balance interacts with the resident biology. The field experiments were conducted using a state-of-the-art real-time field technology that allows instant comparison of field data and 3D numerical modelling results of all physical variables at micro and fine scales and phytoplankton concentration at the group level. The results demonstrate that subtropical lakes present special opportunities and challenges for mitigation of water quality problems in face of global warming.