Thermal structure and hydrodynamic modeling of tropical floodplain lakes

Abstract

Seasonal and daily variations in stratification and mixing have rarely been examined in tropical floodplain lakes. To do so, we combined field measurements of thermal structure with simulations by a 1-dimensional (1-D) hydrodynamic model forced with meteorological data and including hydrologically-forced large seasonal changes in depth and area. Diel cycles of strong daytime stratification and nocturnal mixing were evident in the field data. The model represented these diel changes but underestimated the depth of nocturnal mixing likely due to processes not included in 1-D models. In comparison to simulations forced by local meteorological measurements, use of a gridded reanalysis product resulted in protracted stratification and excessive surface water temperatures. The simulations were extended to an eight-year period, providing the first continuous, multi-year simulation of thermal structure for a tropical floodplain lake. These long-term simulations revealed an inverse relation between water depth and mixing frequency. Improved predictions of how climate change and hydrological alterations will affect stratification, mixing, and ecological function of tropical floodplain lakes require models that represent the large diel and seasonal variations in thermal and hydrological conditions.